Tadalafil is a carboline-based compound with vasodilatory activity. Tadalafil selectively inhibits the cyclic guanosine monophosphate (cGMP)-specific type 5 phosphodiesterase- (PDE-5)-mediated degradation of cGMP, which is found in the smooth muscle of the corpus cavernosa and corpus spongiosum of the penis. Inhibition of cGMP degradation by tadalafil results in prolonged muscle relaxation, vasodilation, and blood engorgement of the corpus cavernosa, and, so, prolonged penile erection.
Tadalafil is an orally adminstered drug used to treat male erectile dysfunction (impotence). It is marketed worldwide under the brand name Cialis. It is a phosphodiesterase 5 (PDE5) inhibitor. Tadalafil’s distinguishing pharmacologic feature is its longer half-life (17.5 hours) compared with Viagra and Levitra (4-5 hours). This longer half-life results in a longer duration of action and is, in part, responsible for the Cialis nickname of the “weekend pill.
Mechanism of Action of Tadalafil
Tadalafil inhibits the cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum located around the penis. Penile erection during sexual stimulation is caused by increased penile blood flow resulting from the relaxation of penile arteries and corpus cavernosal smooth muscle. This response is mediated by the release of nitric oxide (NO) from nerve terminals and endothelial cells, which stimulates the synthesis of cGMP in smooth muscle cells. Cyclic GMP causes smooth muscle relaxation and increased blood flows into the corpus cavernosum. The inhibition of phosphodiesterase type 5 (PDE5) by tadalafil enhances erectile function by increasing the amount of cGMP.This then activates the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation in the corpus cavernosum, resulting in increased inflow of blood and an erection. Tadalafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. This means that, with tadalafil on board, normal sexual stimulation leads to increased levels of cGMP in the corpus cavernosum which leads to better erections. Without sexual stimulation and no activation of the NO/cGMP system, tadalafil should not cause an erection.
Indications of Tadalafil
- Erectile Dysfunction
- Benign Prostatic Hyperplasia
- Pulmonary Hypertension
- Poor sexual desire
- Poor control over intercourse
- Erectile Dysfunction
- Sexual Dysfunction, SSRI Induced
- Persistent or recurrent ejaculation with minimal sexual stimulation before, on, or shortly after penetration and before the patient wishes; and
- Marked personal distress or interpersonal difficulty as a consequence of PE; and
- Poor control over ejaculation; and
- A history of premature ejaculation in the majority of intercourse attempts over the prior 6 months.
- Very short sexual intercourse
- Sexual erectile dysfunction
- Inability to sustain a satisfactory erection to complete intercourse
- Black colour of panish & small size.
- Tadalafil is indicated for the treatment of erectile dysfunction.
Therapeutic Indications
- Used for the treatment of erectile dysfunction.
- is indicated in adults for the treatment of pulmonary arterial hypertension (PAH) classified as WHO functional class II and III, to improve exercise capacity.
- Efficacy has been shown in idiopathic PAH (IPAH) and in PAH related to collagen vascular disease.
- Treatment of erectile dysfunction in adult males.
- In order for tadalafil to be effective, sexual stimulation is required.CIALIS is not indicated for use by women.
- Treatment of erectile dysfunction in adult males.
- In order for tadalafil to be effective, sexual stimulation is required.
- Treatment of the signs and symptoms of benign prostatic hyperplasia in adult males.
- Tadalafil Mylan is not indicated for use by women.
- Treatment of erectile dysfunction in adult males. In order for tadalafil to be effective, sexual stimulation is required.
- Treatment of the signs and symptoms of benign prostatic hyperplasia in adult males.
- Tadalafil Lilly is not indicated for use by women.
- Talmanco is indicated in adults for the treatment of pulmonary arterial hypertension (PAH) classified as WHO functional class II and III, to improve exercise capacity.
- Efficacy has been shown in idiopathic PAH (IPAH) and in PAH related to collagen vascular disease.
Contra – Indications of Tadalafil
- Multiple Myeloma
- Leukemia
- Sickle Cell Anemia
- increased risk of bleeding due to clotting disorder
- increased risk of bleeding
- Alcohol Intoxication
- Pigmentary Retinopathy
- Hearing loss
- Severe Uncontrolled High Blood Pressure
- Unpredictable Severe Constricting Chest Pain
- Narrowing of the Aortic Heart Valve
- hypertrophic cardiomyopathy
- Life-Threatening Irregular Heart Rhythm
- Chronic Heart Failure
- Stroke
- abnormally low blood pressure
- Ulcer from Stomach Acid
- Liver Problems
- Severe Renal Impairment
- Mild to Moderate Kidney Impairment
- Peyronie’s Disease
- Bent Penis On Erection
- Fibrous Tissue Formation in the Penis
- Seizures
- Severe Insufficiency of the Autonomic Nervous System
- Eye Disease Caused by Blood Flow Problems
- Restrictive Cardiomyopathy
Dosage of Tadalafil
Strengths: 2.5 mg, 5 mg; 10 mg; 20 mg;
Erectile Dysfunction
Use as needed for ED
- Initial dose: 10 mg orally once a day, as needed, prior to sexual activity
- Maintenance dose: 5 to 20 mg orally once a day, as needed, prior to sexual activity based on individual efficacy and tolerability
Once a day use for ED
- Initial dose: 2.5 mg orally once a day at approximately the same time, without regard to timing of sexual activity
- Maintenance dose: 2.5 to 5 mg orally once a day based on individual efficacy and tolerability.
Benign Prostatic Hyperplasia (BPH)
- 5 mg orally once a day at approximately the same time, without regard to timing of sexual activity
Pulmonary Hypertension
- 40 mg PO once daily; dividing dose for more frequent dosing is not recommended
- Patients also taking ritonavir: 20 mg PO once daily initially for ≥1 week; may be increased to 40 mg/day on basis of tolerability
- 40 mg orally once a day.
Benign Prostatic Hyperplasia
- 5 mg orally once a day at approximately the same time
Concomitant administration with finasteride
- 5 mg orally once a day at approximately the same time, for up to 26 weeks
Once daily use for ED and BPH
- 5 mg orally once a day at approximately the same time, without regard to timing of sexual activity
Side Effects of Tadalafil
The most common side effects of tadalafil are
- Facial flushing (reddening),
- Headaches,
- Constipation
- sleepiness or unusual drowsiness
- clumsiness or unsteadiness
- dizziness
- drowsiness
- dry mouth
- false sense of well-being
- increased watering of mouth
- lightheadedness
- constipation;
- vision changes;
- breast swelling (in men or women); or
- decreased sex drive, impotence, or difficulty having an orgasm.
- blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
- restless muscle movements in your eyes, tongue, jaw, or neck;
Common
- Drowsiness and lightheadedness the day after taking the medicine.
- Confusion.
- Numbed emotions.
- Visual disturbances such as blurred vision or double vision.
- Shaky movements and unsteady walk (ataxia).
- Loss of memory (amnesia).
- Muscle weakness.
- Dizziness.
- Headache.
- Skin rashes.
- Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain.
- Difficulty in passing urine (urinary retention).
- Changes in sex drive.
- Low blood pressure (hypotension).
- Blood disorders.
- Jaundice.
- Unexpected aggression, restlessness or irritability (tell your doctor if you experience this).
- Nightmares or hallucinations (tell your doctor if you experience this).
Serious
- agitation
- anxiety
- behavioural changes, including aggressiveness, angry outbursts, bizarre behaviour, or decreased inhibitions
- confusion
- increased trouble sleeping
- memory problems
- muscle spasms
- shortness of breath
- signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
- sleepwalking
Drug Interactions of Tadalafil
Tadalafil may interact with following drugs, supplements, & may change the efficacy of drugs
- alpha agonists (e.g., clonidine, methyldopa)
- alpha-blockers (e.g., doxazosin, terazosin)
- angiotensin converting enzyme inhibitors (ACEIs; e.g., captopril, enalapril, ramipril)
- angiotensin receptor blockers (ARBs; e.g., candasartan, irbesartan, losartan)
- aripiprazole
- “azole” antifungals (e.g., itraconazole, ketoconazole, voriconazole)
- barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
- beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
- calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
- carbamazepine
- dexamethasone
- diuretics (water pills; e.g., furosemide, hydrochlorothiazide, )
- fusidic acid
- macrolide antibiotics (e.g., clarithromycin, erythromycin)
- methyldopa
- metronidazole
- phenytoin
- sertraline
- “statins” (e.g., lovastatin, simvastatin, atorvastatin)
- tocilizumab
- tyrosine kinase inhibitors (e.g., dasatinib, imatinib, nilotinib, sunitinib)
Pregnancy & Lactation of Tadalafil
FDA pregnancy Category B
This medication is not used by women.
References
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https://ec.europa.eu/health/documents/community-register/html/h476.htm
https://ec.europa.eu/health/documents/community-register/html/h237.htm
https://ec.europa.eu/health/documents/community-register/html/h961.htm
https://ec.europa.eu/health/documents/community-register/html/h1177.htm
https://ec.europa.eu/health/documents/community-register/html/h1153.htm
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