Gefitinib – Uses, Dosage, Side Effects, Interaction

Gefitinib inhibits the intracellular phosphorylation of numerous tyrosine kinases associated with transmembrane cell surface receptors, including the tyrosine kinases associated with the epidermal growth factor receptor (EGFR-TK). EGFR is expressed on the cell surface of many normal cells and cancer cells.

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Gefitinib is the first selective inhibitor of epidermal growth factor receptor’s (EGFR) tyrosine kinase domain. Thus gefitinib is an EGFR inhibitor. The target protein (EGFR) is a member of a family of receptors (ErbB) which includes Her1(EGFR), Her2(Erb-B2), Her3(Erb-B3), and Her4 (Erb-B4). EGFR is overexpressed in the cells of certain types of human carcinomas – for example in lung and breast cancers. This leads to inappropriate activation of the anti-apoptotic Ras signaling cascade, eventually leading to uncontrolled cell proliferation. Research on gefitinib-sensitive non-small cell lung cancers has shown that a mutation in the EGFR tyrosine kinase domain is responsible for activating anti-apoptotic pathways.^[rx][rx] These mutations tend to confer increased sensitivity to tyrosine kinase inhibitors such as gefitinib and erlotinib. Of the types of non-small cell lung cancer histologies, adenocarcinoma is the type that most often harbors these mutations. These mutations are more commonly seen in Asians, women, and non-smokers (who also tend to more often have adenocarcinoma). Gefitinib inhibits EGFR tyrosine kinase by binding to the adenosine triphosphate (ATP)-the binding site of the enzyme.^[rx] Thus the function of the EGFR tyrosine kinase in activating the anti-apoptotic Ras signal transduction cascade is inhibited, and malignant cells are inhibited.^[rx]

Indications

• For the continued treatment of patients with locally advanced or metastatic non-small cell lung cancer after failure of either platinum-based or docetaxel chemotherapies.
• Iressa is indicated for the treatment of adult patients with locally advanced or metastatic non-small-cell lung cancer with activating mutations of epidermal-growth-factor-receptor tyrosine kinase.
• Gefitinib is a selective tyrosine kinase receptor inhibitor used in the therapy of non-small cell lung cancer.
• Gefitinib is used to treat non-small cell lung cancer that has spread to other parts of the body in people with certain types of tumors. Gefitinib is in a class of medications called kinase inhibitors.
• In Europe, gefitinib is indicated since 2009 in advanced NSCLC in all lines of treatment for patients harboring EGFR mutations. This label was granted after gefitinib was demonstrated as a first-line treatment to significantly improve progression-free survival vs. a platinum doublet regime in patients harboring such mutations. IPASS has been the first of four phases III trials to have confirmed gefitinib superiority in this patient population.
• IRESSA is contraindicated in patients with severe hypersensitivity to gefitinib or to any other component of IRESSA.

Use in Cancer

Gefitinib is approved to treat:

• Non-small cell lung cancer (NSCLC) that has metastasized (spread to other parts of the body). It is used as first-line treatment in patients whose tumors have certain EGFR gene mutations.

Gefitinib is also being studied in the treatment of other types of cancer.

Contraindications

• a type of inflammation of the lung called interstitial pneumonitis
• a condition where there is a formation of fibrous tissue in the lung called pulmonary fibrosis
• liver problems
• severe renal impairment
• pregnancy
• a patient who is producing milk and breastfeeding

Dosage

Strengths: 250 mg

Non-Small Cell Lung Cancer

• 250 mg orally once a day until disease progression or unacceptable toxicity
• Select patients for the first-line treatment of metastatic NSCLC with this drug based on the presence of EGFR exon 19 deletions or exon 21 L858R mutations in their tumor or plasma specimens.
  

  NOTE: For patients who have difficulty swallowing tablets immerse the tablet in 4 to 8 ounces of water (noncarbonated) and stir until dispersed (about 15 minutes). Drink the liquid or administer through a nasogastric tube. Rinse the container with 4 to 8 ounces of water and drink or administer through nasogastric tube.

Dose Adjustments

Withhold therapy for up to 14 days for the following adverse drug reactions and resume when fully resolved to Grade 1:

• Acute onset or worsening of pulmonary symptoms (e.g., dyspnea, cough, fever)
• Grade 2 or higher in alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) elevations
• Grade 3 or higher diarrhea
• Severe or worsening ocular disorders including keratitis
• Grade 3 or higher skin reactions

Permanently discontinue therapy for:

• Confirmed interstitial lung disease (ILD)
• Severe hepatic impairment
• GI perforation
• Persistent ulcerative keratitis

Concomitant use with strong CYP450 3A4 inducers:

• Avoid concomitant use if possible.
• If concomitant use is required, increase dose to 500 mg orally once a day (in the absence of severe adverse drug reaction); resume at 250 mg dose 7 days after discontinuation of the strong CYP450 3A4 inducer.

Concomitant use with proton-pump inhibitor/H2 receptor antagonist/antacid:

• Avoid concomitant use if possible.
• If concomitant use is required, take this drug 12 hours after the last dose of the proton-pump inhibitor or 12 hours before the next dose of the proton-pump inhibitor.
• Take this drug 6 hours after the last dose of the H2-receptor antagonist or antacid, or 6 hours before the next dose of the H2-receptor antagonist or antacid.

Administration Advice:

• Therapy should be initiated and supervised by a physician experienced in the use of anticancer therapies.
• This drug should be taken at about the same time each day, with or without food.
• A missed dose should not be taken within 12 hours of the next dose.

Side Effects

The Most Common

• dry skin
• itching
• rash
• acne
• mouth sores
• weakness
• new or worsening shortness of breath, cough, or fever
• severe or ongoing diarrhea
• severe abdominal pain
• loss of appetite
• eye pain, redness, or irritation
• vision changes
• watery eyes
• eye sensitivity to light
• hives
• blisters or peeling skin
• swelling of the eyes, face, lips, tongue, throat, hands, arms, feet, ankles or lower legs
• nausea
• vomiting
• yellowing of the skin or eyes
• dark urine
• pale stools
• pain or discomfort in the right upper stomach area

More common

• Abdominal or stomach pain or tenderness
• clay-colored stools
• dark urine
• decreased appetite
• diarrhea, severe
• fever
• headache
• itching or skin rash
• loss of appetite
• nausea and vomiting
• swelling of the feet or lower legs
• unusual tiredness or weakness
• yellow eyes or skin
• Burning, dry, or itching eyes
• chest pain
• chills
• cough
• difficult breathing
• discharge or excessive tearing
• dry eyes
• a general feeling of discomfort or illness
• redness, pain, or swelling of the eye, eyelid, or inner lining of the eyelid
• thickening of bronchial secretions
• troubled breathing
• troubled or quick, shallow breathing

Rare

• severe or ongoing diarrhea;
• sudden chest pain or discomfort, new or worsening cough with fever, trouble breathing;
• blurred vision, watery eyes, eye pain or redness, eyes being more sensitive to light;
• liver problems–nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
• signs of stomach bleeding–severe stomach pain, bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds; or
• severe skin reaction–fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.
• Blistering, peeling, or loosening of the skin
• bloody, black, or tarry stools
• eye redness, irritation, or pain
• heartburn
• indigestion
• joint or muscle pain
• red skin lesions, often with a purple center
• severe abdominal or stomach pain, cramping, or burning
• sore throat
• sores, ulcers, or white spots in the mouth or on the lips
• vomiting of material that looks like coffee grounds, severe and continuing

Drug Interactions

DRUG	INTERACTION
Abaloparatide	The therapeutic efficacy of Abaloparatide can be decreased when used in combination with Gefitinib.
Abametapir	The serum concentration of Gefitinib can be increased when it is combined with Abametapir.
Abatacept	The metabolism of Gefitinib can be increased when combined with Abatacept.
Abemaciclib	Gefitinib may decrease the excretion rate of Abemaciclib which could result in a higher serum level.
Abiraterone	The metabolism of Gefitinib can be decreased when combined with Abiraterone.
Acalabrutinib	The metabolism of Gefitinib can be decreased when combined with Acalabrutinib.
Acebutolol	The metabolism of Gefitinib can be decreased when combined with Acebutolol.
Acenocoumarol	Gefitinib may increase the anticoagulant activities of Acenocoumarol.
Acetaminophen	The serum concentration of Acetaminophen can be increased when it is combined with Gefitinib.
Adalimumab	The metabolism of Gefitinib can be increased when combined with Adalimumab.
Afatinib	Gefitinib may decrease the excretion rate of Afatinib which could result in a higher serum level.
Alectinib	Alectinib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Alfentanil	The metabolism of Alfentanil can be decreased when combined with Gefitinib.
Allopurinol	Gefitinib may decrease the excretion rate of Allopurinol which could result in a higher serum level.
Almasilate	Almasilate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Almotriptan	The metabolism of Almotriptan can be decreased when combined with Gefitinib.
Alogliptin	The metabolism of Alogliptin can be decreased when combined with Gefitinib.
Alpelisib	The serum concentration of Alpelisib can be increased when it is combined with Gefitinib.
Alprazolam	The metabolism of Alprazolam can be decreased when combined with Gefitinib.
Aluminium	Aluminium phosphate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Aluminum	Aluminum hydroxide can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Ambrisentan	The metabolism of Ambrisentan can be decreased when combined with Gefitinib.
Aminophenazone	The metabolism of Aminophenazone can be decreased when combined with Gefitinib.
Amiodarone	The metabolism of Gefitinib can be decreased when combined with Amiodarone.
Amitriptyline	The metabolism of Amitriptyline can be decreased when combined with Gefitinib.
Amoxapine	The metabolism of Amoxapine can be decreased when combined with Gefitinib.
Amphetamine	The metabolism of Amphetamine can be decreased when combined with Gefitinib.
Amprenavir	The metabolism of Gefitinib can be decreased when combined with Amprenavir.
Anakinra	The metabolism of Gefitinib can be increased when combined with Anakinra.
Antipyrine	The metabolism of Antipyrine can be decreased when combined with Gefitinib.
Apalutamide	The metabolism of Gefitinib can be increased when combined with Apalutamide.
Apixaban	Gefitinib may decrease the excretion rate of Apixaban which could result in a higher serum level.
Apomorphine	The metabolism of Apomorphine can be decreased when combined with Gefitinib.
Apremilast	The metabolism of Gefitinib can be increased when combined with Apremilast.
Aprepitant	The metabolism of Gefitinib can be decreased when combined with Aprepitant.
Arformoterol	The metabolism of Arformoterol can be decreased when combined with Gefitinib.
Aripiprazole	The metabolism of Aripiprazole can be decreased when combined with Gefitinib.
Aripiprazole	The metabolism of Aripiprazole lauroxil can be decreased when combined with Gefitinib.
Armodafinil	The metabolism of Gefitinib can be increased when combined with Armodafinil.
Artemether	The metabolism of Artemether can be decreased when combined with Gefitinib.
Artenimol	The metabolism of Gefitinib can be decreased when combined with Artenimol.
Articaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Articaine.
Asenapine	Asenapine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Astemizole	The metabolism of Astemizole can be decreased when combined with Gefitinib.
Asunaprevir	The metabolism of Gefitinib can be decreased when combined with Asunaprevir.
Atazanavir	The metabolism of Gefitinib can be decreased when combined with Atazanavir.
Atenolol	The metabolism of Atenolol can be decreased when combined with Gefitinib.
Atomoxetine	The metabolism of Atomoxetine can be decreased when combined with Gefitinib.
Atorvastatin	The metabolism of Atorvastatin can be decreased when combined with Gefitinib.
Avanafil	The serum concentration of Avanafil can be increased when it is combined with Gefitinib.
Avatrombopag	Avatrombopag may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Axitinib	The metabolism of Axitinib can be decreased when combined with Gefitinib.
Azelastine	The metabolism of Gefitinib can be decreased when combined with Azelastine.
Beclomethasone	Beclomethasone dipropionate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Belumosudil	Belumosudil may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Benzatropine	The metabolism of Benzatropine can be decreased when combined with Gefitinib.
Benzocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Benzocaine.
Benzyl alcohol	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Benzyl alcohol.
Bepridil	The metabolism of Gefitinib can be decreased when combined with Bepridil.
Berotralstat	The serum concentration of Berotralstat can be increased when it is combined with Gefitinib.
Betamethasone	The metabolism of Gefitinib can be increased when combined with Betamethasone.
Betamethasone	The metabolism of Gefitinib can be increased when combined with Betamethasone phosphate.
Betaxolol	The metabolism of Betaxolol can be decreased when combined with Gefitinib.
Bimekizumab	The metabolism of Gefitinib can be increased when combined with Bimekizumab.
Biperiden	The metabolism of Gefitinib can be decreased when combined with Biperiden.
Bismuth	Bismuth subnitrate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Boceprevir	The metabolism of Gefitinib can be decreased when combined with Boceprevir.
Bortezomib	The metabolism of Bortezomib can be decreased when combined with Gefitinib.
Brexpiprazole	The metabolism of Brexpiprazole can be decreased when combined with Gefitinib.
Brigatinib	Gefitinib may decrease the excretion rate of Brigatinib which could result in a higher serum level.
Budesonide	The metabolism of Gefitinib can be increased when combined with Budesonide.
Bupivacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Bupivacaine.
Buprenorphine	Buprenorphine may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Bupropion	The metabolism of Gefitinib can be decreased when combined with Bupropion.
Buspirone	The metabolism of Buspirone can be decreased when combined with Gefitinib.
Butacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Butacaine.
Butamben	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Butamben.
Cabazitaxel	The metabolism of Cabazitaxel can be decreased when combined with Gefitinib.
Caffeine	Caffeine may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Calcium	Calcium carbonate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Canakinumab	The metabolism of Gefitinib can be increased when combined with Canakinumab.
Cannabidiol	Cannabidiol may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Capmatinib	The serum concentration of Gefitinib can be increased when it is combined with Capmatinib.
Capsaicin	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Capsaicin.
Carbamazepine	The metabolism of Gefitinib can be increased when combined with Carbamazepine.
Carbimazole	The therapeutic efficacy of Carbimazole can be decreased when used in combination with Gefitinib.
Carvedilol	The metabolism of Carvedilol can be decreased when combined with Gefitinib.
Celecoxib	The metabolism of Gefitinib can be decreased when combined with Celecoxib.
Celiprolol	The metabolism of Celiprolol can be decreased when combined with Gefitinib.
Cenobamate	The serum concentration of Gefitinib can be decreased when it is combined with Cenobamate.
Cerivastatin	Gefitinib may decrease the excretion rate of Cerivastatin which could result in a higher serum level.
Certolizumab	The metabolism of Gefitinib can be increased when combined with Certolizumab pegol.
Cevimeline	The metabolism of Cevimeline can be decreased when combined with Gefitinib.
Chloramphenicol	The metabolism of Gefitinib can be decreased when combined with Chloramphenicol.
Chloroprocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Chloroprocaine.
Chloroquine	The metabolism of Gefitinib can be decreased when combined with Chloroquine.
Chlorpheniramine	The metabolism of Gefitinib can be decreased when combined with Chlorpheniramine.
Chlorpromazine	The metabolism of Gefitinib can be decreased when combined with Chlorpromazine.
Chlorzoxazone	The metabolism of Chlorzoxazone can be decreased when combined with Gefitinib.
Cholecalciferol	The metabolism of Gefitinib can be decreased when combined with Cholecalciferol.

Cholesterol	Cholesterol may increase the excretion rate of Gefitinib which could result in a lower serum level and potentially a reduction in efficacy.
Ciclesonide	The metabolism of Ciclesonide can be decreased when combined with Gefitinib.
Cilostazol	The metabolism of Cilostazol can be decreased when combined with Gefitinib.
Cimetidine	Cimetidine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Cinacalcet	The metabolism of Gefitinib can be decreased when combined with Cinacalcet.
Cinchocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Cinchocaine.
Cinnarizine	The metabolism of Cinnarizine can be decreased when combined with Gefitinib.
Ciprofloxacin	The metabolism of Gefitinib can be decreased when combined with Ciprofloxacin.
Cisapride	The metabolism of Gefitinib can be decreased when combined with Cisapride.
Citalopram	The metabolism of Gefitinib can be decreased when combined with Citalopram.
Cladribine	Gefitinib may decrease the excretion rate of Cladribine which could result in a higher serum level.
Clarithromycin	The metabolism of Gefitinib can be decreased when combined with Clarithromycin.
Clemastine	The metabolism of Gefitinib can be decreased when combined with Clemastine.
Clevidipine	The metabolism of Clevidipine can be decreased when combined with Gefitinib.
Clindamycin	The metabolism of Clindamycin can be decreased when combined with Gefitinib.
Clobazam	The metabolism of Gefitinib can be decreased when combined with Clobazam.
Clobetasol	The metabolism of Gefitinib can be increased when combined with Clobetasol propionate.
Clofarabine	Gefitinib may decrease the excretion rate of Clofarabine which could result in a higher serum level.
Clofazimine	Clofazimine may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Clomipramine	The metabolism of Clomipramine can be decreased when combined with Gefitinib.
Clonidine	The metabolism of Clonidine can be decreased when combined with Gefitinib.
Clopidogrel	The metabolism of Clopidogrel can be decreased when combined with Gefitinib.
Clozapine	The metabolism of Gefitinib can be decreased when combined with Clozapine.
Cobicistat	The metabolism of Gefitinib can be decreased when combined with Cobicistat.
Cocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Cocaine.
Codeine	The metabolism of Codeine can be decreased when combined with Gefitinib.
Conivaptan	The metabolism of Gefitinib can be decreased when combined with Conivaptan.
Conjugated	Gefitinib may decrease the excretion rate of Conjugated estrogens which could result in a higher serum level.
Copanlisib	The metabolism of Copanlisib can be decreased when combined with Gefitinib.
Cortisone	The metabolism of Gefitinib can be increased when combined with Cortisone acetate.
Crizotinib	The metabolism of Crizotinib can be decreased when combined with Gefitinib.
Curcumin	The metabolism of Gefitinib can be decreased when combined with Curcumin.
Cyclophosphamide	The metabolism of Cyclophosphamide can be decreased when combined with Gefitinib.
Cyclosporine	The metabolism of Gefitinib can be decreased when combined with Cyclosporine.
Dabrafenib	The serum concentration of Gefitinib can be decreased when it is combined with Dabrafenib.
Daclatasvir	Daclatasvir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Dacomitinib	The metabolism of Dacomitinib can be decreased when combined with Gefitinib.
Dactinomycin	Gefitinib may decrease the excretion rate of Dactinomycin which could result in a higher serum level.
Danazol	The metabolism of Gefitinib can be decreased when combined with Danazol.
Dapagliflozin	The metabolism of Dapagliflozin can be decreased when combined with Gefitinib.
Dapsone	The metabolism of Gefitinib can be decreased when combined with Dapsone.
Darbepoetin	The risk or severity of Thrombosis can be increased when Darbepoetin alfa is combined with Gefitinib.
Darifenacin	The metabolism of Gefitinib can be decreased when combined with Darifenacin.
Darolutamide	The serum concentration of Gefitinib can be increased when it is combined with Darolutamide.
Darunavir	The metabolism of Gefitinib can be decreased when combined with Darunavir.
Dasabuvir	Dasabuvir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Dasatinib	The metabolism of Dasatinib can be decreased when combined with Gefitinib.
Daunorubicin	Gefitinib may decrease the excretion rate of Daunorubicin which could result in a higher serum level.
Debrisoquine	The metabolism of Debrisoquine can be decreased when combined with Gefitinib.
Delafloxacin	Gefitinib may decrease the excretion rate of Delafloxacin which could result in a higher serum level.
Delavirdine	The metabolism of Gefitinib can be decreased when combined with Delavirdine.
Desipramine	The metabolism of Gefitinib can be decreased when combined with Desipramine.
Desvenlafaxine	The metabolism of Gefitinib can be decreased when combined with Desvenlafaxine.
Deutetrabenazine	The metabolism of Deutetrabenazine can be decreased when combined with Gefitinib.
Dexamethasone	The metabolism of Gefitinib can be increased when combined with Dexamethasone.
Dexamethasone	Dexamethasone acetate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Dexchlorpheniram	The metabolism of Gefitinib can be decreased when combined with Dexchlorpheniramine maleate.
Dexfenfluramine	The metabolism of Dexfenfluramine can be decreased when combined with Gefitinib.
Dexlansoprazole	Dexlansoprazole can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Dexmedetomidine	The metabolism of Gefitinib can be decreased when combined with Dexmedetomidine.
Dextroamphetam	The metabolism of Dextroamphetamine can be decreased when combined with Gefitinib.
Dextromethorphan	The metabolism of Dextromethorphan can be decreased when combined with Gefitinib.
Dextropropoxy	The metabolism of Gefitinib can be decreased when combined with Dextropropoxyphene.
Diacerein	The metabolism of Gefitinib can be decreased when combined with Diacerein.
Diazepam	The metabolism of Diazepam can be decreased when combined with Gefitinib.
Dicoumarol	Gefitinib may increase the anticoagulant activities of Dicoumarol.
Diethylstilbestrol	Diethylstilbestrol may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Difluocortolone	The metabolism of Gefitinib can be increased when combined with Difluocortolone.
Dihydrocodeine	The metabolism of Dihydrocodeine can be decreased when combined with Gefitinib.
Diltiazem	The metabolism of Gefitinib can be decreased when combined with Diltiazem.
Dimethyl sulfoxide	The metabolism of Gefitinib can be decreased when combined with Dimethyl sulfoxide.
Diphenhydramine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Diphenhydramine.
Disulfiram	The metabolism of Disulfiram can be decreased when combined with Gefitinib.
Docetaxel	The metabolism of Docetaxel can be decreased when combined with Gefitinib.
Dolasetron	The metabolism of Dolasetron can be decreased when combined with Gefitinib.
Dolutegravir	Gefitinib may decrease the excretion rate of Dolutegravir which could result in a higher serum level.
Domperidone	The metabolism of Domperidone can be decreased when combined with Gefitinib.
Donepezil	Gefitinib may decrease the excretion rate of Donepezil which could result in a higher serum level.
Doravirine	The metabolism of Doravirine can be decreased when combined with Gefitinib.
Dosulepin	The metabolism of Gefitinib can be decreased when combined with Dosulepin.
Doxazosin	The metabolism of Doxazosin can be decreased when combined with Gefitinib.
Doxepin	Doxepin can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Doxorubicin	Gefitinib may decrease the excretion rate of Doxorubicin which could result in a higher serum level.
Dronabinol	The metabolism of Gefitinib can be decreased when combined with Dronabinol.
Dronedarone	The metabolism of Gefitinib can be decreased when combined with Dronedarone.
Duloxetine	The metabolism of Gefitinib can be decreased when combined with Duloxetine.
Dutasteride	The metabolism of Dutasteride can be decreased when combined with Gefitinib.
Duvelisib	Gefitinib may decrease the excretion rate of Duvelisib which could result in a higher serum level.
Dyclonine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Dyclonine.
Efavirenz	The metabolism of Gefitinib can be decreased when combined with Efavirenz.
Elagolix	The metabolism of Elagolix can be decreased when combined with Gefitinib.
Elbasvir	Elbasvir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Eletriptan	The metabolism of Eletriptan can be decreased when combined with Gefitinib.
Elexacaftor	The metabolism of Elexacaftor can be decreased when combined with Gefitinib.
Eliglustat	The metabolism of Gefitinib can be decreased when combined with Eliglustat.
Eltrombopag	Eltrombopag may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Elvitegravir	The metabolism of Gefitinib can be decreased when combined with Elvitegravir.
Emapalumab	The metabolism of Gefitinib can be increased when combined with Emapalumab.
Enasidenib	The metabolism of Enasidenib can be decreased when combined with Gefitinib.
Encainide	The metabolism of Encainide can be decreased when combined with Gefitinib.

Encorafenib	The metabolism of Encorafenib can be decreased when combined with Gefitinib.
Entacapone	The metabolism of Gefitinib can be decreased when combined with Entacapone.
Enzalutamide	The metabolism of Gefitinib can be increased when combined with Enzalutamide.
Epinastine	Epinastine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Eplerenone	The metabolism of Eplerenone can be decreased when combined with Gefitinib.
Ergotamine	The metabolism of Gefitinib can be decreased when combined with Ergotamine.
Erlotinib	The metabolism of Erlotinib can be decreased when combined with Gefitinib.
Ertugliflozin	Gefitinib may decrease the excretion rate of Ertugliflozin which could result in a higher serum level.
Erythromycin	The metabolism of Gefitinib can be decreased when combined with Erythromycin.
Erythropoietin	The risk or severity of Thrombosis can be increased when Erythropoietin is combined with Gefitinib.
Escitalopram	The serum concentration of Gefitinib can be increased when it is combined with Escitalopram.
Esmolol	The metabolism of Esmolol can be decreased when combined with Gefitinib.
Esomeprazole	Esomeprazole can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Estradiol	Estradiol may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Estradiol acetate	Estradiol acetate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Estradiol	Estradiol benzoate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Estradiol	Estradiol cypionate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Estradiol	Estradiol dienanthate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Estradiol	Estradiol valerate may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Etanercept	The metabolism of Gefitinib can be increased when combined with Etanercept.
Ethambutol	The metabolism of Gefitinib can be decreased when combined with Ethambutol.
Ethinylestradiol	The metabolism of Ethinylestradiol can be decreased when combined with Gefitinib.
Ethyl chloride	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Ethyl chloride.
Etidocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Etidocaine.
Etoposide	The metabolism of Etoposide can be decreased when combined with Gefitinib.
Etoricoxib	The metabolism of Gefitinib can be decreased when combined with Etoricoxib.
Everolimus	The metabolism of Gefitinib can be decreased when combined with Everolimus.
Ezetimibe	Gefitinib may decrease the excretion rate of Ezetimibe which could result in a higher serum level.
Famotidine	Famotidine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Febuxostat	The excretion of Gefitinib can be decreased when combined with Febuxostat.
Fedratinib	Fedratinib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Felodipine	The metabolism of Gefitinib can be decreased when combined with Felodipine.
Fenfluramine	The metabolism of Gefitinib can be decreased when combined with Fenfluramine.
Fesoterodine	The metabolism of Fesoterodine can be decreased when combined with Gefitinib.
Fexinidazole	The metabolism of Fexinidazole can be decreased when combined with Gefitinib.
Finasteride	The metabolism of Finasteride can be decreased when combined with Gefitinib.
Flecainide	The metabolism of Flecainide can be decreased when combined with Gefitinib.
Fluconazole	The metabolism of Gefitinib can be decreased when combined with Fluconazole.
Fluindione	Gefitinib may increase the anticoagulant activities of Fluindione.
Flunarizine	The metabolism of Flunarizine can be decreased when combined with Gefitinib.
Fluocinonide	The metabolism of Gefitinib can be increased when combined with Fluocinonide.
Fluocortolone	The metabolism of Gefitinib can be increased when combined with Fluocortolone.
Fluorouracil	Gefitinib may decrease the excretion rate of Fluorouracil which could result in a higher serum level.
Fluoxetine	The serum concentration of Gefitinib can be increased when it is combined with Fluoxetine.
Fluphenazine	The metabolism of Gefitinib can be decreased when combined with Fluphenazine.
Flutamide	The metabolism of Flutamide can be decreased when combined with Gefitinib.
Fluticasone	The metabolism of Gefitinib can be decreased when combined with Fluticasone.
Fluticasone	The metabolism of Gefitinib can be decreased when combined with Fluticasone furoate.
Fluticasone	The metabolism of Gefitinib can be decreased when combined with Fluticasone propionate.
Fluvastatin	The metabolism of Fluvastatin can be decreased when combined with Gefitinib.
Fluvoxamine	The metabolism of Gefitinib can be decreased when combined with Fluvoxamine.
Folic acid	Gefitinib may decrease the excretion rate of Folic acid which could result in a higher serum level.
Follitropin	The therapeutic efficacy of Follitropin can be decreased when used in combination with Gefitinib.
Formoterol	The metabolism of Formoterol can be decreased when combined with Gefitinib.
Fosnetupitant	The metabolism of Gefitinib can be decreased when combined with Fosnetupitant.
Fosphenytoin	The metabolism of Gefitinib can be increased when combined with Fosphenytoin.
Fostamatinib	Fostamatinib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Fostemsavir	Gefitinib may decrease the excretion rate of Fostemsavir which could result in a higher serum level.
Fusidic acid	The metabolism of Gefitinib can be decreased when combined with Fusidic acid.
Galantamine	The metabolism of Galantamine can be decreased when combined with Gefitinib.
Gilteritinib	Gilteritinib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Givosiran	The serum concentration of Gefitinib can be increased when it is combined with Givosiran.
Glasdegib	Gefitinib may decrease the excretion rate of Glasdegib which could result in a higher serum level.
Glecaprevir	Gefitinib may decrease the excretion rate of Glecaprevir which could result in a higher serum level.
Glyburide	Gefitinib may decrease the excretion rate of Glyburide which could result in a higher serum level.
Glycerol	The metabolism of Gefitinib can be decreased when combined with Glycerol phenylbutyrate.
Golimumab	The metabolism of Gefitinib can be increased when combined with Golimumab.
Grazoprevir	Grazoprevir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Halofantrine	The metabolism of Gefitinib can be decreased when combined with Halofantrine.
Haloperidol	The serum concentration of Haloperidol can be increased when it is combined with Gefitinib.
Hydrocodone	The metabolism of Hydrocodone can be decreased when combined with Gefitinib.
Hydrocortisone	The metabolism of Hydrocortisone can be decreased when combined with Gefitinib.
Hydrocortisone	The metabolism of Hydrocortisone acetate can be decreased when combined with Gefitinib.
Hydrocortisone	The metabolism of Hydrocortisone butyrate can be decreased when combined with Gefitinib.
Hydrocortisone	The metabolism of Hydrocortisone cypionate can be decreased when combined with Gefitinib.
Hydrocortisone	The metabolism of Hydrocortisone phosphate can be decreased when combined with Gefitinib.
Hydrotalcite	Hydrotalcite can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Hydroxychloroquine	The metabolism of Gefitinib can be decreased when combined with Hydroxychloroquine.
Hydroxyprogester	The metabolism of Hydroxyprogesterone caproate can be decreased when combined with Gefitinib.
Hydroxyzine	The metabolism of Gefitinib can be decreased when combined with Hydroxyzine.
Ibrutinib	The metabolism of Ibrutinib can be decreased when combined with Gefitinib.
Idarubicin	The metabolism of Idarubicin can be decreased when combined with Gefitinib.
Idelalisib	Gefitinib may decrease the excretion rate of Idelalisib which could result in a higher serum level.
Ifosfamide	The metabolism of Ifosfamide can be decreased when combined with Gefitinib.
Iloperidone	The metabolism of Iloperidone can be decreased when combined with Gefitinib.
Imatinib	The serum concentration of Gefitinib can be increased when it is combined with Imatinib.
Imipramine	The metabolism of Gefitinib can be decreased when combined with Imipramine.
Indinavir	The metabolism of Gefitinib can be decreased when combined with Indinavir.
Infliximab	The metabolism of Gefitinib can be increased when combined with Infliximab.
Ipecac	The metabolism of Ipecac can be decreased when combined with Gefitinib.
Irinotecan	Gefitinib may decrease the excretion rate of Irinotecan which could result in a higher serum level.
Isavuconazole	The metabolism of Gefitinib can be decreased when combined with Isavuconazole.
Isavuconazonium	The metabolism of Gefitinib can be decreased when combined with Isavuconazonium.
Isoniazid	The metabolism of Gefitinib can be decreased when combined with Isoniazid.
Isradipine	The metabolism of Gefitinib can be decreased when combined with Isradipine.
Istradefylline	Istradefylline may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Itraconazole	The metabolism of Gefitinib can be decreased when combined with Itraconazole.
Ivacaftor	The metabolism of Ivacaftor can be decreased when combined with Gefitinib.
Ivermectin	Gefitinib may decrease the excretion rate of Ivermectin which could result in a higher serum level.
Ivosidenib	The metabolism of Gefitinib can be increased when combined with Ivosidenib

Ketoconazole	The metabolism of Gefitinib can be decreased when combined with Ketoconazole.
Labetalol	The metabolism of Gefitinib can be decreased when combined with Labetalol.
Lamivudine	Gefitinib may decrease the excretion rate of Lamivudine which could result in a higher serum level.
Lansoprazole	Lansoprazole can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Lapatinib	The metabolism of Lapatinib can be decreased when combined with Gefitinib.
Lasmiditan	The serum concentration of Gefitinib can be increased when it is combined with Lasmiditan.
Ledipasvir	Ledipasvir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Leflunomide	Gefitinib may decrease the excretion rate of Leflunomide which could result in a higher serum level.
Lemborexant	The metabolism of Lemborexant can be decreased when combined with Gefitinib.
Lenvatinib	Gefitinib may decrease the excretion rate of Lenvatinib which could result in a higher serum level.
Lercanidipine	The metabolism of Lercanidipine can be decreased when combined with Gefitinib.
Letermovir	Letermovir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Levamlodipine	The metabolism of Levamlodipine can be decreased when combined with Gefitinib.
Levobetaxolol	The metabolism of Levobetaxolol can be decreased when combined with Gefitinib.
Levobupivacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Levobupivacaine.
Levoketoconazole	The metabolism of Gefitinib can be decreased when combined with Levoketoconazole.
Levomilnacipran	The metabolism of Levomilnacipran can be decreased when combined with Gefitinib.
Levonorgestrel	The metabolism of Levonorgestrel can be decreased when combined with Gefitinib.
Levothyroxine	The therapeutic efficacy of Levothyroxine can be decreased when used in combination with Gefitinib.
Lidocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Lidocaine.
Linagliptin	The metabolism of Gefitinib can be decreased when combined with Linagliptin.
Liothyronine	The therapeutic efficacy of Liothyronine can be decreased when used in combination with Gefitinib.
Liotrix	The therapeutic efficacy of Liotrix can be decreased when used in combination with Gefitinib.
Lisdexamfetamine	The metabolism of Lisdexamfetamine can be decreased when combined with Gefitinib.
Lisuride	The metabolism of Lisuride can be decreased when combined with Gefitinib.
Lofexidine	The metabolism of Lofexidine can be decreased when combined with Gefitinib.
Lonafarnib	The metabolism of Gefitinib can be decreased when combined with Lonafarnib.
Lopinavir	The metabolism of Gefitinib can be decreased when combined with Lopinavir.
Lorcaserin	The metabolism of Gefitinib can be decreased when combined with Lorcaserin.
Lorlatinib	The metabolism of Lorlatinib can be decreased when combined with Gefitinib.
Lorpiprazole	The metabolism of Lorpiprazole can be decreased when combined with Gefitinib.
Lovastatin	The metabolism of Gefitinib can be decreased when combined with Lovastatin.
Lumacaftor	The metabolism of Gefitinib can be increased when combined with Lumacaftor.
Lumefantrine	The metabolism of Gefitinib can be decreased when combined with Lumefantrine.
Lusutrombopag	Gefitinib may decrease the excretion rate of Lusutrombopag which could result in a higher serum level.
Magaldrate	Magaldrate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Magnesium	Magnesium carbonate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Magnesium	Magnesium hydroxide can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Magnesium oxide	Magnesium oxide can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Magnesium silicate	Magnesium silicate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Magnesium	Magnesium trisilicate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Manidipine	The metabolism of Gefitinib can be decreased when combined with Manidipine.
Maprotiline	The metabolism of Maprotiline can be decreased when combined with Gefitinib.
Maribavir	Maribavir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Mavacamten	The serum concentration of Gefitinib can be decreased when it is combined with Mavacamten.
Meclizine	The metabolism of Meclizine can be decreased when combined with Gefitinib.
Meloxicam	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Meloxicam.
Mephenytoin	The metabolism of Mephenytoin can be decreased when combined with Gefitinib.
Mepivacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Mepivacaine.
Meprednisone	The metabolism of Gefitinib can be increased when combined with Meprednisone.
Mepyramine	The metabolism of Gefitinib can be decreased when combined with Mepyramine.
Mesoridazine	The metabolism of Mesoridazine can be decreased when combined with Gefitinib.
Metamfetamine	The metabolism of Metamfetamine can be decreased when combined with Gefitinib.
Methadone	The metabolism of Gefitinib can be decreased when combined with Methadone.
Methantheline	Methantheline can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Methimazole	The metabolism of Gefitinib can be decreased when combined with Methimazole.
Methotrexate	Gefitinib may decrease the excretion rate of Methotrexate which could result in a higher serum level.
Methotrimeprazine	The metabolism of Gefitinib can be decreased when combined with Methotrimeprazine.
Methoxy	The risk or severity of Thrombosis can be increased when Methoxy polyethylene glycol-epoetin beta is combined with Gefitinib.
Methoxyflurane	The metabolism of Methoxyflurane can be decreased when combined with Gefitinib.
Methylene blue	The metabolism of Gefitinib can be decreased when combined with Methylene blue.
Metoclopramide	The metabolism of Gefitinib can be decreased when combined with Metoclopramide.
Metoprolol	The metabolism of Gefitinib can be decreased when combined with Metoprolol.
Metreleptin	The metabolism of Gefitinib can be increased when combined with Metreleptin.
Metronidazole	The metabolism of Metronidazole can be decreased when combined with Gefitinib.
Mexiletine	The metabolism of Mexiletine can be decreased when combined with Gefitinib.
Mianserin	The metabolism of Mianserin can be decreased when combined with Gefitinib.
Miconazole	The metabolism of Gefitinib can be decreased when combined with Miconazole.
Midazolam	The metabolism of Midazolam can be decreased when combined with Gefitinib.
Midostaurin	The metabolism of Gefitinib can be increased when combined with Midostaurin.
Mifepristone	The metabolism of Gefitinib can be decreased when combined with Mifepristone.
Milnacipran	The metabolism of Gefitinib can be decreased when combined with Milnacipran.
Minaprine	The metabolism of Minaprine can be decreased when combined with Gefitinib.
Mirabegron	The serum concentration of Gefitinib can be increased when it is combined with Mirabegron.
Mirtazapine	The metabolism of Mirtazapine can be decreased when combined with Gefitinib.
Mitotane	The metabolism of Gefitinib can be increased when combined with Mitotane.
Mitoxantrone	Gefitinib may decrease the excretion rate of Mitoxantrone which could result in a higher serum level.
Mobocertinib	The metabolism of Mobocertinib can be decreased when combined with Gefitinib.
Moclobemide	The metabolism of Gefitinib can be decreased when combined with Moclobemide.
Modafinil	The metabolism of Gefitinib can be increased when combined with Modafinil.
Mometasone	The metabolism of Gefitinib can be increased when combined with Mometasone furoate.
Mycophenolate	Gefitinib may decrease the excretion rate of Mycophenolate mofetil which could result in a higher serum level.
Nadolol	The metabolism of Nadolol can be decreased when combined with Gefitinib.
Naloxone	The metabolism of Gefitinib can be decreased when combined with Naloxone.
Nateglinide	The metabolism of Nateglinide can be decreased when combined with Gefitinib.
Nebivolol	The metabolism of Nebivolol can be decreased when combined with Gefitinib.
Nefazodone	The metabolism of Gefitinib can be decreased when combined with Nefazodone.
Nelfinavir	The metabolism of Gefitinib can be decreased when combined with Nelfinavir.
Netupitant	The metabolism of Gefitinib can be decreased when combined with Netupitant.
Nevirapine	The metabolism of Gefitinib can be decreased when combined with Nevirapine.
Niacin	The metabolism of Gefitinib can be decreased when combined with Niacin.
Nicardipine	The metabolism of Gefitinib can be decreased when combined with Nicardipine.
Nicergoline	The metabolism of Nicergoline can be decreased when combined with Gefitinib.
Nifedipine	The metabolism of Nifedipine can be decreased when combined with Gefitinib.
Nilotinib	The metabolism of Gefitinib can be decreased when combined with Nilotinib.
Nilvadipine	The metabolism of Gefitinib can be decreased when combined with Nilvadipine.
Nisoldipine	The metabolism of Nisoldipine can be decreased when combined with Gefitinib.
Nitrendipine	The metabolism of Nitrendipine can be decreased when combined with Gefitinib.
Nitrofurantoin	Gefitinib may decrease the excretion rate of Nitrofurantoin which could result in a higher serum level.
Nizatidine	Nizatidine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.

Norethisterone	The metabolism of Norethisterone can be decreased when combined with Gefitinib.
Nortriptyline	The metabolism of Nortriptyline can be decreased when combined with Gefitinib.
Novobiocin	Novobiocin may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Olanzapine	Olanzapine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Olaparib	The metabolism of Olaparib can be decreased when combined with Gefitinib.
Oliceridine	The metabolism of Oliceridine can be decreased when combined with Gefitinib.
Ombitasvir	Gefitinib may decrease the excretion rate of Ombitasvir which could result in a higher serum level.
Omeprazole	Omeprazole can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Ondansetron	The metabolism of Ondansetron can be decreased when combined with Gefitinib.
Opium	The metabolism of Opium can be decreased when combined with Gefitinib.
Oritavancin	The metabolism of Gefitinib can be decreased when combined with Oritavancin.
Orphenadrine	The metabolism of Gefitinib can be decreased when combined with Orphenadrine.
Osilodrostat	The metabolism of Gefitinib can be decreased when combined with Osilodrostat.
Osimertinib	Gefitinib may decrease the excretion rate of Osimertinib which could result in a higher serum level.
Ospemifene	The metabolism of Gefitinib can be decreased when combined with Ospemifene.
Oteseconazole	The serum concentration of Gefitinib can be increased when it is combined with Oteseconazole.
Oxaliplatin	Gefitinib may decrease the excretion rate of Oxaliplatin which could result in a higher serum level.
Oxamniquine	The metabolism of Gefitinib can be decreased when combined with Oxamniquine.
Oxcarbazepine	The metabolism of Gefitinib can be increased when combined with Oxcarbazepine.
Oxetacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Oxetacaine.
Oxprenolol	The metabolism of Gefitinib can be decreased when combined with Oxprenolol.
Oxybuprocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Oxybuprocaine.
Oxybutynin	The metabolism of Gefitinib can be decreased when combined with Oxybutynin.
Oxycodone	The metabolism of Oxycodone can be decreased when combined with Gefitinib.
Oxymorphone	The metabolism of Oxymorphone can be decreased when combined with Gefitinib.
Ozanimod	Gefitinib may decrease the excretion rate of Ozanimod which could result in a higher serum level.
Paclitaxel	The metabolism of Paclitaxel can be decreased when combined with Gefitinib.
Pacritinib	The serum concentration of Gefitinib can be increased when it is combined with Pacritinib.
Palbociclib	Gefitinib may decrease the excretion rate of Palbociclib which could result in a higher serum level.
Paliperidone	The metabolism of Paliperidone can be decreased when combined with Gefitinib.
Palonosetron	The metabolism of Palonosetron can be decreased when combined with Gefitinib.
Panobinostat	The metabolism of Gefitinib can be decreased when combined with Panobinostat.
Pantoprazole	Pantoprazole can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Parathyroid	The therapeutic efficacy of Parathyroid hormone can be decreased when used in combination with Gefitinib.
Paritaprevir	Paritaprevir may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Paroxetine	The metabolism of Gefitinib can be decreased when combined with Paroxetine.
Pazopanib	Gefitinib may decrease the excretion rate of Pazopanib which could result in a higher serum level.
Peginesatide	The risk or severity of Thrombosis can be increased when Peginesatide is combined with Gefitinib.
Peginterferon	The metabolism of Gefitinib can be decreased when combined with Peginterferon alfa-2b.
Penbutolol	The metabolism of Penbutolol can be decreased when combined with Gefitinib.
Pentamidine	The metabolism of Pentamidine can be decreased when combined with Gefitinib.
Pentobarbital	The metabolism of Gefitinib can be increased when combined with Pentobarbital.
Perampanel	The metabolism of Perampanel can be decreased when combined with Gefitinib.
Perhexiline	The metabolism of Gefitinib can be decreased when combined with Perhexiline.
Perphenazine	The metabolism of Gefitinib can be decreased when combined with Perphenazine.
Phenformin	The metabolism of Phenformin can be decreased when combined with Gefitinib.
Phenindione	Gefitinib may increase the anticoagulant activities of Phenindione.
Phenobarbital	The metabolism of Gefitinib can be increased when combined with Phenobarbital.
Phenol	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Phenol.
Phenprocoumon	Gefitinib may increase the anticoagulant activities of Phenprocoumon.
Phenylbutyric acid	The metabolism of Gefitinib can be decreased when combined with Phenylbutyric acid.
Phenytoin	The metabolism of Gefitinib can be increased when combined with Phenytoin.
Pibrentasvir	Gefitinib may decrease the excretion rate of Pibrentasvir which could result in a higher serum level.
Pimozide	The metabolism of Pimozide can be decreased when combined with Gefitinib.
Pindolol	The metabolism of Pindolol can be decreased when combined with Gefitinib.
Piperazine	The metabolism of Piperazine can be decreased when combined with Gefitinib.
Pipotiazine	The metabolism of Gefitinib can be decreased when combined with Pipotiazine.
Pirfenidone	The metabolism of Pirfenidone can be decreased when combined with Gefitinib.
Pitavastatin	Gefitinib may decrease the excretion rate of Pitavastatin which could result in a higher serum level.
Pitolisant	The serum concentration of Gefitinib can be decreased when it is combined with Pitolisant.
Ponatinib	The metabolism of Ponatinib can be decreased when combined with Gefitinib.
Ponesimod	The metabolism of Ponesimod can be decreased when combined with Gefitinib.
Posaconazole	The metabolism of Gefitinib can be decreased when combined with Posaconazole.
Potassium Iodide	The therapeutic efficacy of Potassium Iodide can be decreased when used in combination with Gefitinib.
Potassium	The therapeutic efficacy of Potassium perchlorate can be decreased when used in combination with Gefitinib.
Practolol	The metabolism of Practolol can be decreased when combined with Gefitinib.
Pralatrexate	Gefitinib may decrease the excretion rate of Pralatrexate which could result in a higher serum level.
Pralsetinib	Gefitinib may decrease the excretion rate of Pralsetinib which could result in a higher serum level.
Pramocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Pramocaine.
Pravastatin	Pravastatin may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Praziquantel	The metabolism of Praziquantel can be decreased when combined with Gefitinib.
Prazosin	Gefitinib may decrease the excretion rate of Prazosin which could result in a higher serum level.
Prednisolone	The metabolism of Gefitinib can be increased when combined with Prednisolone phosphate.
Prednisone	The metabolism of Gefitinib can be increased when combined with Prednisone acetate.
Prilocaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Prilocaine.
Primaquine	The metabolism of Gefitinib can be decreased when combined with Primaquine.
Primidone	The metabolism of Gefitinib can be increased when combined with Primidone.
Procainamide	The metabolism of Procainamide can be decreased when combined with Gefitinib.
Procaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Procaine.
Prochlorperazine	The metabolism of Prochlorperazine can be decreased when combined with Gefitinib.
Progesterone	Progesterone may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Proguanil	The metabolism of Gefitinib can be decreased when combined with Proguanil.
Promazine	The metabolism of Promazine can be decreased when combined with Gefitinib.
Promethazine	Promethazine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Propafenone	The metabolism of Gefitinib can be decreased when combined with Propafenone.
Proparacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Proparacaine.
Propoxycaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Propoxycaine.
Propranolol	The metabolism of Propranolol can be decreased when combined with Gefitinib.
Propylthiouracil	The therapeutic efficacy of Propylthiouracil can be decreased when used in combination with Gefitinib.
Protirelin	The therapeutic efficacy of Protirelin can be decreased when used in combination with Gefitinib.
Quetiapine	The metabolism of Quetiapine can be decreased when combined with Gefitinib.
Quinidine	The metabolism of Gefitinib can be decreased when combined with Quinidine.
Quinine	The metabolism of Gefitinib can be decreased when combined with Quinine.
Rabeprazole	Rabeprazole can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Raloxifene	Gefitinib may decrease the excretion rate of Raloxifene which could result in a higher serum level.
Ranitidine	Ranitidine can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Ranolazine	The serum concentration of Gefitinib can be increased when it is combined with Ranolazine.
Reboxetine	The metabolism of Gefitinib can be decreased when combined with Reboxetine.
Regorafenib	Regorafenib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Relugolix	The metabolism of Relugolix can be decreased when combined with Gefitinib.

Remoxipride	The metabolism of Remoxipride can be decreased when combined with Gefitinib.
Reserpine	The metabolism of Gefitinib can be increased when combined with Reserpine.
Revefenacin	Gefitinib may decrease the excretion rate of Revefenacin which could result in a higher serum level.
Ribociclib	The metabolism of Gefitinib can be decreased when combined with Ribociclib.
Rifampicin	The metabolism of Gefitinib can be increased when combined with Rifampicin.
Rifamycin	The metabolism of Gefitinib can be increased when combined with Rifamycin.
Rifapentine	The metabolism of Gefitinib can be increased when combined with Rifapentine.
Rilonacept	The metabolism of Gefitinib can be increased when combined with Rilonacept.
Rilpivirine	Rilpivirine may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Riluzole	Gefitinib may decrease the excretion rate of Riluzole which could result in a higher serum level.
Rimegepant	The serum concentration of Rimegepant can be increased when it is combined with Gefitinib.
Riociguat	Gefitinib may decrease the excretion rate of Riociguat which could result in a higher serum level.
Ripretinib	Gefitinib may decrease the excretion rate of Ripretinib which could result in a higher serum level.
Risperidone	The metabolism of Risperidone can be decreased when combined with Gefitinib.
Ritonavir	The serum concentration of Gefitinib can be increased when it is combined with Ritonavir.
Rivaroxaban	Gefitinib may decrease the excretion rate of Rivaroxaban which could result in a higher serum level.
Rolapitant	The metabolism of Gefitinib can be decreased when combined with Rolapitant.
Romidepsin	The metabolism of Romidepsin can be decreased when combined with Gefitinib.
Ropeginterferon	The metabolism of Gefitinib can be decreased when combined with Ropeginterferon alfa-2b.
Ropivacaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Ropivacaine.
Rosuvastatin	Gefitinib may decrease the excretion rate of Rosuvastatin which could result in a higher serum level.
Rotigotine	The metabolism of Gefitinib can be decreased when combined with Rotigotine.
Roxadustat	The serum concentration of Gefitinib can be increased when it is combined with Roxadustat.
Rucaparib	The metabolism of Gefitinib can be decreased when combined with Rucaparib.
Rupatadine	The metabolism of Rupatadine can be decreased when combined with Gefitinib.
Safinamide	Safinamide may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Salmeterol	The metabolism of Salmeterol can be decreased when combined with Gefitinib.
Salmon calcitonin	The therapeutic efficacy of Salmon calcitonin can be decreased when used in combination with Gefitinib.
Saquinavir	The metabolism of Gefitinib can be decreased when combined with Saquinavir.
Natalizumab	The serum concentration of Gefitinib can be decreased when it is combined with Satralizumab.
Saxagliptin	The metabolism of Saxagliptin can be decreased when combined with Gefitinib.
Secukinumab	The metabolism of Gefitinib can be increased when combined with Secukinumab.
Selegiline	The metabolism of Selegiline can be decreased when combined with Gefitinib.
Selumetinib	Gefitinib may decrease the excretion rate of Selumetinib which could result in a higher serum level.
Sertindole	The metabolism of Sertindole can be decreased when combined with Gefitinib.
Sertraline	The metabolism of Sertraline can be decreased when combined with Gefitinib.
Sildenafil	The metabolism of Gefitinib can be decreased when combined with Sildenafil.
Siltuximab	The metabolism of Gefitinib can be increased when combined with Siltuximab.
Simeprevir	The metabolism of Gefitinib can be decreased when combined with Simeprevir.
Simvastatin	The metabolism of Simvastatin can be decreased when combined with Gefitinib.
Sirolimus	The metabolism of Sirolimus can be decreased when combined with Gefitinib.
Sodium bicarbon	Sodium bicarbonate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Sodium zirconium	Sodium zirconium cyclosilicate can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Sofosbuvir	Gefitinib may decrease the excretion rate of Sofosbuvir which could result in a higher serum level.
Solifenacin	The metabolism of Solifenacin can be decreased when combined with Gefitinib.
Somatrogon	The metabolism of Gefitinib can be increased when combined with Somatrogon.
Sorafenib	The metabolism of Sorafenib can be decreased when combined with Gefitinib.
Sotagliflozin	Sotagliflozin may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Sotalol	The metabolism of Sotalol can be decreased when combined with Gefitinib.
Sotorasib	The serum concentration of Gefitinib can be decreased when it is combined with Sotorasib.
St. John’s Wort	The metabolism of Gefitinib can be increased when combined with St. John’s Wort.
Stiripentol	The metabolism of Gefitinib can be decreased when combined with Stiripentol.
Sulfaphenazole	The metabolism of Gefitinib can be decreased when combined with Sulfaphenazole.
Sulfasalazine	Gefitinib may decrease the excretion rate of Sulfasalazine which could result in a higher serum level.
Sumatriptan	Gefitinib may decrease the excretion rate of Sumatriptan which could result in a higher serum level.
Sunitinib	The metabolism of Sunitinib can be decreased when combined with Gefitinib.
Tacrolimus	The metabolism of Tacrolimus can be decreased when combined with Gefitinib.
Tadalafil	The metabolism of Tadalafil can be decreased when combined with Gefitinib.
Tafamidis	The serum concentration of Gefitinib can be increased when it is combined with Tafamidis.
Tafenoquine	The metabolism of Tafenoquine can be decreased when combined with Gefitinib.
Talazoparib	Gefitinib may decrease the excretion rate of Talazoparib which could result in a higher serum level.
Tamoxifen	The metabolism of Tamoxifen can be decreased when combined with Gefitinib.
Tamsulosin	The metabolism of Tamsulosin can be decreased when combined with Gefitinib.
Taurocholic acid	Taurocholic acid may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Tazemetostat	Gefitinib may decrease the excretion rate of Tazemetostat which could result in a higher serum level.
Tegafur	The metabolism of Tegafur can be decreased when combined with Gefitinib.
Tegaserod	The metabolism of Gefitinib can be decreased when combined with Tegaserod.
Telaprevir	The metabolism of Gefitinib can be decreased when combined with Telaprevir.
Telithromycin	The metabolism of Gefitinib can be decreased when combined with Telithromycin.
Telmisartan	Telmisartan may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Telotristat ethyl	The serum concentration of Gefitinib can be decreased when it is combined with Telotristat ethyl.
Temsirolimus	The metabolism of Temsirolimus can be decreased when combined with Gefitinib.
Teniposide	The metabolism of Teniposide can be decreased when combined with Gefitinib.
Tenofovir alafenamide	The serum concentration of Tenofovir alafenamide can be increased when it is combined with Gefitinib.
Tepotinib	Tepotinib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Terbinafine	The metabolism of Gefitinib can be decreased when combined with Terbinafine.
Terfenadine	The metabolism of Gefitinib can be decreased when combined with Terfenadine.
Teriflunomide	Gefitinib may decrease the excretion rate of Teriflunomide which could result in a higher serum level.
Teriparatide	The therapeutic efficacy of Teriparatide can be decreased when used in combination with Gefitinib.
Testosterone	Gefitinib may decrease the excretion rate of Testosterone which could result in a higher serum level.
Testosterone	Gefitinib may decrease the excretion rate of Testosterone cypionate which could result in a higher serum level.
Testosterone	Gefitinib may decrease the excretion rate of Testosterone enanthate which could result in a higher serum level.
Tetrabenazine	The metabolism of Tetrabenazine can be decreased when combined with Gefitinib.
Tetracaine	The risk or severity of methemoglobinemia can be increased when Gefitinib is combined with Tetracaine.
Tezacaftor	The metabolism of Tezacaftor can be decreased when combined with Gefitinib.
Thalidomide	The metabolism of Gefitinib can be increased when combined with Thalidomide.
Theophylline	The metabolism of Theophylline can be decreased when combined with Gefitinib.
Thioridazine	The metabolism of Gefitinib can be decreased when combined with Thioridazine.
Thyroid, porcine	The therapeutic efficacy of Thyroid, porcine can be decreased when used in combination with Gefitinib.
Thyrotropin alfa	The therapeutic efficacy of Thyrotropin alfa can be decreased when used in combination with Gefitinib.
Ticagrelor	The metabolism of Ticagrelor can be decreased when combined with Gefitinib.
Ticlopidine	The metabolism of Gefitinib can be decreased when combined with Ticlopidine.
Timolol	The metabolism of Timolol can be decreased when combined with Gefitinib.
Tiotropium	The metabolism of Tiotropium can be decreased when combined with Gefitinib.
Tipranavir	The metabolism of Gefitinib can be decreased when combined with Tipranavir.
Tivozanib	Tivozanib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Tocilizumab	The metabolism of Gefitinib can be increased when combined with Tocilizumab.
Tolterodine	The metabolism of Tolterodine can be decreased when combined with Gefitinib.
Topotecan	Gefitinib may decrease the excretion rate of Topotecan which could result in a higher serum level.
Trabectedin	The metabolism of Trabectedin can be decreased when combined with Gefitinib.

Tramadol	The metabolism of Tramadol can be decreased when combined with Gefitinib.
Tranylcypromine	The metabolism of Gefitinib can be decreased when combined with Tranylcypromine.
Trastuzumab emtansine	The metabolism of Trastuzumab emtansine can be decreased when combined with Gefitinib.
Trazodone	The metabolism of Trazodone can be decreased when combined with Gefitinib.
Tretinoin	The metabolism of Tretinoin can be decreased when combined with Gefitinib.
Triamcinolone	The metabolism of Gefitinib can be increased when combined with Triamcinolone.
Triazolam	The metabolism of Triazolam can be decreased when combined with Gefitinib.
Triclabendazole	The metabolism of Gefitinib can be decreased when combined with Triclabendazole.
Trilaciclib	Gefitinib may decrease the excretion rate of Trilaciclib which could result in a higher serum level.
Trimipramine	The metabolism of Trimipramine can be decreased when combined with Gefitinib.
Tripelennamine	The metabolism of Gefitinib can be decreased when combined with Tripelennamine.
Troglitazone	The metabolism of Gefitinib can be decreased when combined with Troglitazone.
Troleandomycin	The metabolism of Gefitinib can be decreased when combined with Troleandomycin.
Trospium	The metabolism of Gefitinib can be decreased when combined with Trospium.
Tucatinib	The metabolism of Tucatinib can be decreased when combined with Gefitinib.
Ubrogepant	The serum concentration of Ubrogepant can be increased when it is combined with Gefitinib.
Udenafil	The metabolism of Udenafil can be decreased when combined with Gefitinib.
Umeclidinium	The metabolism of Umeclidinium can be decreased when combined with Gefitinib.
Valbenazine	The metabolism of Valbenazine can be decreased when combined with Gefitinib.
Vandetanib	Vandetanib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Vardenafil	The metabolism of Vardenafil can be decreased when combined with Gefitinib.
Velpatasvir	Gefitinib may decrease the excretion rate of Velpatasvir which could result in a higher serum level.
Vemurafenib	Gefitinib may decrease the excretion rate of Vemurafenib which could result in a higher serum level.
Venetoclax	The metabolism of Gefitinib can be decreased when combined with Venetoclax.
Venlafaxine	The metabolism of Gefitinib can be decreased when combined with Venlafaxine.
Verapamil	The metabolism of Gefitinib can be decreased when combined with Verapamil.
Vernakalant	The metabolism of Vernakalant can be decreased when combined with Gefitinib.
Vilazodone	The metabolism of Gefitinib can be decreased when combined with Vilazodone.
Viloxazine	The metabolism of Gefitinib can be decreased when combined with Viloxazine.
Vinblastine	The metabolism of Gefitinib can be decreased when combined with Vinblastine.
Vincristine	The metabolism of Vincristine can be decreased when combined with Gefitinib.
Vinorelbine	Gefitinib may increase the neutropenic activities of Vinorelbine.
Vismodegib	Vismodegib may decrease the excretion rate of Gefitinib which could result in a higher serum level.
Vonoprazan	Vonoprazan can cause a decrease in the absorption of Gefitinib resulting in a reduced serum concentration and potentially a decrease in efficacy.
Voriconazole	The serum concentration of Gefitinib can be increased when it is combined with Voriconazole.
Vortioxetine	The metabolism of Vortioxetine can be decreased when combined with Gefitinib.
Voxilaprevir	Gefitinib may decrease the excretion rate of Voxilaprevir which could result in a higher serum level.
Warfarin	Gefitinib may increase the anticoagulant activities of Warfarin.
Yohimbine	The metabolism of Yohimbine can be decreased when combined with Gefitinib.
Zaleplon	The metabolism of Zaleplon can be decreased when combined with Gefitinib.
Zidovudine	Gefitinib may decrease the excretion rate of Zidovudine which could result in a higher serum level.
Zimelidine	The metabolism of Gefitinib can be decreased when combined with Zimelidine.
Ziprasidone	The metabolism of Gefitinib can be decreased when combined with Ziprasidone.
Zolpidem	The metabolism of Zolpidem can be decreased when combined with Gefitinib.
Zonisamide	The metabolism of Zonisamide can be decreased when combined with Gefitinib.
Zuclopenthixol	The metabolism of Zuclopenthixol can be decreased when combined with Gefitinib.

Pregnancy and Lactation

AU TGA pregnancy category: C
US FDA pregnancy category: Not assigned.

Pregnancy

Based on its mechanism of action and animal data, IRESSA can cause fetal harm when administered to a pregnant
woman. In animal reproductive studies, oral administration of gefitinib from organogenesis through weaning resulted in fetotoxicity and neonatal death at doses below the recommended human dose (see Animal Data). Advise pregnant women of the potential hazard to a fetus or potential risk for loss of the pregnancy. The background risk of major birth defects and miscarriage for the indicated population is unknown; however, the background risk in the U.S. general population of major birth defects is 2-4% and miscarriage is 15-20% of clinically
recognized pregnancies

Lactation

No information is available on the clinical use of gefitinib during breastfeeding. Because gefitinib is 90% bound to plasma proteins, the amount in milk is likely to be low. However, its half-life is about 48 hours and it might accumulate in the infant. The manufacturer recommends that breastfeeding be discontinued during gefitinib therapy.

How should this medicine be used?

Gefitinib comes as a tablet to take by mouth. It is usually taken with or without food once a day. Take gefitinib at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take gefitinib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you are unable to swallow the tablets, you may dissolve them in water. Place one tablet in 4 to 8 ounces (120 to 240 mL) of plain, noncarbonated drinking water. Stir with a spoon for about 15 minutes until the tablet is dissolved. Drink the mixture right away. Rinse the glass with another 4 to 8 ounces (120 to 240 mL) of water and drink the rinse water right away to be sure that you swallow all of the medication.

Your doctor may delay or permanently stop your treatment if you experience certain side effects. Be sure to tell your doctor how you are feeling during your treatment with gefitinib.

What special precautions should I follow?

Before taking gefitinib,

• tell your doctor and pharmacist if you are allergic to gefitinib, any other medications, or any of the ingredients in gefitinib tablets. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Be sure to mention any of the following: anticoagulants (‘blood thinners) such as warfarin (Coumadin, Jantoven); antifungals such as itraconazole (Onmel, Sporanox) and ketoconazole (Nizoral); metoprolol (Lopressor, Toprol XL, in Dutoprol); phenytoin (Dilantin, Phenytek); and tricyclic antidepressants such as imipramine (Tofranil) and amitriptyline. Many other medications may interact with gefitinib, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• if you are taking an antacid or an H₂ blocker medication for indigestion, heartburn, or ulcers such as cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid), or ranitidine (Zantac), take them at least 6 hours before or 6 hours after taking gefitinib.
• if you are taking a proton pump inhibitor medication for indigestion, heartburn, or ulcers such as esomeprazole (Nexium), lansoprazole (Prevacid), omeprazole (Prilosec), pantoprazole (Protonix), or rabeprazole (AcipHex), take it at least 12 hours before or at least 12 hours after taking gefitinib.
• tell your doctor if you have or have ever had pulmonary fibrosis (scarring of the lungs) or other lung or breathing problems, eye or vision problems, or liver disease.
• tell your doctor if you are pregnant or plan to become pregnant. Gefitinib may cause infertility (difficulty becoming pregnant) in females. However, you should use birth control to prevent pregnancy during your treatment with gefitinib and for at least 2 weeks after you stop taking the medication. If you become pregnant while taking gefitinib, call your doctor. Gefitinib may harm the fetus and increase the risk of pregnancy loss.
• tell your doctor if you are breastfeeding. You should not breastfeed while you are taking gefitinib.

References

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