Furosemide is a sulfamoyl anthranilic acid derivative, also known as frusemide, and a potent loop diuretic. Furosemide is widely used to treat hypertension and edema. This agent is highly bound to albumin and is largely excreted unchanged in the urine.
Furosemide belongs to the class of medications called loops diuretics. It is used to treat edema (fluid retention) that occurs with congestive heart failure and disorders of the liver, kidney, and lung. It is a medication used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. It is also used to control mild to moderate high blood pressure. It is a diuretic with fast onset and short duration that is used for edema and chronic renal insufficiency.It can be taken intravenously or by mouth. When taken by mouth it typically begins working within an hour while intravenously it typically begins working within five minutes.
Mechanism of Action of Furosemide
Furosemide, a loop diuretic, inhibits water reabsorption in the nephron by blocking the sodium-potassium-chloride cotransporter (NKCC2) in the thick ascending limb of the loop of Henle. This is achieved through competitive inhibition at the chloride binding site on the cotransporter, thus preventing the transport of sodium from the lumen of the loop of Henle into the basolateral interstitium. Consequently, the lumen becomes more hypertonic while the interstitium becomes less hypertonic, which in turn diminishes the osmotic gradient for water reabsorption throughout the nephron. Because the thick ascending limb is responsible for 25% of sodium reabsorption in the nephron, furosemide is a very potent diuretic.
Indications of Furosemide
- Edema
- High Blood Pressure (Hypertension)
- Heart Failure
- Liver cirrhosis,
- Kidney impairment,
- Nephrotic syndrome,
- Adjunct therapy for swelling of the brain or lungs
- Ascites
- Hypercalcemia
- Nonobstructive Oliguria
- Oliguria
- Pulmonary Edema
- Renal Failure
- Renal Transplant
Contra-Indications of Furosemide
- Diabetes
- Gout
- Low amount of magnesium in the blood
- Low amount of calcium in the blood
- Low amount of sodium in the blood
- Low amount of potassium in the blood
- Low amount of chloride in the blood
- Hearing loss
- Heart attack
- Blood pressure drop upon standing
- Abnormally low blood pressure
- Blockage of the urinary bladder
- Enlarged prostate
- Systemic lupus erythematosus
- Blood circulation failure due to a serious heart condition
- The high amount of uric acid in the blood
- Azotemia
- Decreased blood volume
- Acid Base imbalance of the blood toward the basic side
- The absence of urine formation
- Low amount of protein in the blood
- Pancreatitis
Dosage of Furosemide
Strengths: 20 mg; 40 mg; 80 mg
Hypertension
Oral
- Initial dose: 80 mg/day, usually divided into 40 mg orally twice a day
Edema
Oral
- Initial dose: 20 to 80 mg orally once; may repeat with the same dose or increase by 20 or 40 mg no sooner than 6 to 8 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day (e.g., at 8 am and 2 pm).
- Maximum dose: 600 mg/day in patients with clinically severe edematous states
IV/IM
- Initial dose: 20 to 40 mg IV (slowly over 1 to 2 minutes) or IM once; may repeat with the same dose or increase by 20 mg no sooner than 2 hours after the previous dose until the desired diuretic effect has been obtained.
Nephrotic Syndrome
Oral
- Initial dose: 20 to 80 mg orally once; may repeat with the same dose or increase by 20 or 40 mg no sooner than 6 to 8 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day (e.g., at 8 am and 2 pm).
- Maximum dose: 600 mg/day in patients with clinically severe edematous states
IV/IM
- Initial dose: 20 to 40 mg IV (slowly over 1 to 2 minutes) or IM once; may repeat with the same dose or increase by 20 mg no sooner than 2 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day.
Renal Failure
Oral
- Initial dose: 20 to 80 mg orally once; may repeat with the same dose or increase by 20 or 40 mg no sooner than 6 to 8 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day (e.g., at 8 am and 2 pm).
- Maximum dose: 600 mg/day in patients with clinically severe edematous states
IV/IM
- Initial dose: 20 to 40 mg IV (slowly over 1 to 2 minutes) or IM once; may repeat with the same dose or increase by 20 mg no sooner than 2 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day.
Congestive Heart Failure
Oral
- Initial dose: 20 to 80 mg orally once; may repeat with the same dose or increase by 20 or 40 mg no sooner than 6 to 8 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day (e.g., at 8 am and 2 pm).
- Maximum dose: 600 mg/day in patients with clinically severe edematous states
IV/IM
- Initial dose: 20 to 40 mg IV (slowly over 1 to 2 minutes) or IM once; may repeat with the same dose or increase by 20 mg no sooner than 2 hours after the previous dose until the desired diuretic effect has been obtained.
- Maintenance dose: Administer the dose that provided the desired diuretic effect once or twice a day.
Pulmonary Edema
- 40 mg IV slowly over 1 to 2 minutes; if a satisfactory response doesn’t occur within one hour, may increase to 80 mg IV slowly over 1 to 2 minutes.
Side Effects of Furosemide
Most common
- dry mouth,
- Increase the feeling of thurst
- increase the frequency of urination
- Abdominal or stomach discomfort
- low blood pressure,
- difficult, burning, or painful urination
- increased potassium blood levels (hyperkalemia),
- low blood sugar (hypoglycemia), and
- diarrhea
- symptoms of weakness, muscle pain (myalgia)
- abdominal pain (GI complaints), lactic acidosis (rare)
- low blood levels of vitamin B-12
- nausea,vomiting
- chest discomfort
- chills, dizziness
- bloating/abdominal distention
- constipation
- heartburn
More common
- chest pain;
- Abdominal or stomach discomfort
- cough or hoarseness
- decreased appetite
- diarrhea
- fast or shallow breathing
- trouble breathing; or
- dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, confusion, chest pain, shortness of breath, uneven heartbeats, seizure)
- lower back or side pain
- muscle pain or cramping
- painful or difficult urination
Less common
- dry mouth
- feeling of thirst
- weakness
- drowsiness
- restlessness
- muscle pains or cramps
- fast or abnormal heartbeat
- severe nausea or vomiting
- tiredness
- weakness
- dry hair and skin
- increased feelings of being cold
- pain when you eat or drink
- severe nausea or vomiting
Drug Interactions of Furosemide
- Aspirin and other salicylates
- Other diuretics (e.g. ethacrynic acid, hydrochlorothiazide)
- Analgesics: increased risk of kidney damage (nephrotoxicity) with nonsteroidal anti-inflammatory drugs; antagonism of diuretic effect with NSAIDs
- Anti-arrhythmics: risk of cardiac toxicity with antiarrhythmics if hypokalemia occurs, effects of lidocaine and mexiletine antagonized
- angiotensin II receptor antagonists (e.g., irbesartan, losartan)
- antiseizure medication (e.g., carbamazepine, phenobarbital, phenytoin, topiramate)
- beta2-agonists (e.g., formoterol, salbutamol, salmeterol)
- corticosteroids (e.g., hydrocortisone, prednisone)
- cyclosporine
- diabetes medications (e.g., glyburide, rosiglitazone)
- methotrexate
- methylphenidate
- monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, phenelzine, rasagiline, tranylcypromine)
- nonsteroidal anti-inflammatory medications (NSAIDs; e.g., ibuprofen, indomethacin, naproxen)
- pentoxifylline
- phenytoin
- phosphodiesterase-5-inhibitors (e.g., sildenafil, tadalafil, vardenafil)
- probenecid
- risperidone
- rituximab
- sucralfate
Pregnancy & Lactation of Furosemide
FDA Pregnancy Category C
Pregnancy
The effect of taking furosemide on the unborn baby during pregnancy is unknown. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
Lactation
Furosemide passes into breast milk and may also partially reduce the amount of breast milk produced. If you are a breastfeeding mother and are taking furosemide, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding.
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