furosemide
Apo-Furosemide ◆, Lasix, Lasix Special ◆, Novosemide ◆, Uritol ◆

Available forms
Available by prescription only
Injection: 10 mg/ml
Solution: 10 mg/ml, 40 mg/5 ml
Tablets: 20 mg, 40 mg, 80 mg

Indications and dosages
 Acute pulmonary edema. Adults: 40 mg I.V. injected slowly; then 80 mg I.V. within 1 hour, p.r.n.
Infants and children: 1 mg/kg I.M. or I.V. q 2 hours until response is achieved; maximum dose is 6 mg/kg daily.
 Edema. Adults: 20 to 80 mg P.O. daily in morning, with second dose given in 6 to 8 hours, carefully adjusted up to 600 mg daily, p.r.n. Or, 20 to 40 mg I.M. or I.V. Increased by 20 mg q 2 hours until desired response is achieved. I.V. dosage should be given slowly over 1 to 2 minutes.
Infants and children: 2 mg/kg daily P.O., increased by 1 to 2 mg/kg in 6 to 8 hours, p.r.n., carefully adjusted not to exceed 6 mg/kg daily.
 Hypertension. Adults: 40 mg P.O. b.i.d. Adjust dosage according to response.
 Hypercalcemia ◇. Adults: 80 to 100 mg I.V. q 1 to 2 hours. Or, 120 mg P.O. daily.
Elderly patients: Reduced dosages may be indicated.

Pharmacodynamics
Diuretic action: Loop diuretics inhibit sodium and chloride reabsorption in the proximal part of the ascending loop of Henle, promoting the excretion of sodium, water, chloride, and potassium.
Antihypertensive action: This drug effect may be the result of renal and peripheral vasodilatation and a temporary increase in glomerular filtration rate and a decrease in peripheral vascular resistance.

Pharmacokinetics
Absorption: About 60% of a dose is absorbed from the GI tract after oral administration. Food delays oral absorption but doesn’t alter diuretic response. Diuresis begins in 30 to 60 minutes and peaks 1 to 2 hours after oral administration. Diuresis follows I.V. administration within 5 minutes and peaks in 20 to 60 minutes.
Distribution: About 95% is plasma protein-bound. It crosses the placental barrier and appears in breast milk.
Metabolism: Metabolized minimally by the liver.
Excretion: About 50% to 80% of a dose is excreted in urine; plasma half-life is about 30 minutes. Duration of action is 6 to 8 hours after oral administration and about 2 hours after I.V. administration.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug and patients with anuria, hepatic coma, or severe electrolyte depletion. Contraindicated if increased azotemia, oliguria, or progressive renal disease occur during therapy. Use cautiously in pregnant women, patients with sulfa allergy, and in those with hepatic cirrhosis.

Interactions
Drug-drug. Aminoglycoside antibiotics, cisplatin, ethacrynic acid: May potentiate ototoxicity. Don’t use together.
Amphotericin B, corticosteroids, corticotropin, metolazone: Increases risk of hypokalemia. Monitor potassium levels.
Antidiabetics: Decreases hypoglycemic effects. Monitor glucose levels.
Antihypertensives: Increases risk of hypotension. Check blood pressure frequently.
Cardiac glycosides, lithium, neuromuscular blockers: Increases risk of toxicity. Monitor potassium levels.
NSAIDs: May inhibit diuretic response. Use together cautiously.
Salicylates: May cause salicylate toxicity. Use together cautiously.
Sucralfate: May reduce diuretic and antihypertensive effect. Separate administration by 2 hours.
Drug-herb. Aloe: May increase drug effects. Tell patient to use together cautiously.
Dandelion: May interfere with diuretic activity. Discourage use together.
Ginseng: Decreases effect of loop diuretic. Discourage use together.
Drug-lifestyle. Sun exposure: Potentiates photosensitivity reactions. Advise patient to take precautions.

Adverse reactions
CNS: vertigo, headache, dizziness, paresthesia, restlessness, fever.
CV: volume depletion and dehydration, orthostatic hypotension, thrombophlebitis with I.V. administration.
EENT: transient deafness with too-rapid I.V. injection, blurred vision.
GI: abdominal discomfort and pain, diarrhea, anorexia, nausea, vomiting, constipation, PANCREATITIS
.
GU: nocturia, azotemia, polyuria, frequent urination, renal failure, oliguria.
Hematologic: agranulocytosis, leukopenia, thrombocytopenia, anemia, aplastic anemia.
Metabolic: hypokalemia; hypochloremic alkalosis; asymptomatic hyperuricemia; fluid and electrolyte imbalances, including dilutional hyponatremia, hypocalcemia, hypomagnesemia; hyperglycemia; impaired glucose tolerance.
Musculoskeletal: muscle spasm, weakness.
Skin: dermatitis, purpura, transient pain at I.M. injection site.

Effects on lab test results
• May increase BUN, creatinine, glucose, cholesterol, and uric acid levels. May decrease potassium, sodium, calcium, and magnesium levels.
• May decrease hemoglobin, hematocrit, and granulocyte, WBC, and platelet counts.

Overdose and treatment
Signs and symptoms of overdose include profound electrolyte and volume depletion, which may precipitate circulatory collapse.
 Treatment is chiefly supportive; replace fluids and electrolytes.

Special considerations
• Give I.V. furosemide slowly, over 1 to 2 minutes. For I.V. infusion, dilute furosemide in D₅W, normal saline solution, or lactated Ringer’s solution, and use within 24 hours. If high-dose furosemide therapy is needed, administer as a controlled infusion not exceeding 4 mg/minute.
• Sorbitol content of oral preparations may cause diarrhea, especially at high doses.
• Monitor serum potassium and CBC before treatment and periodically throughout therapy.
Pregnant patients
• Use cautiously in pregnant women.
Breast-feeding patients
• Drug shouldn’t be used by breast-feeding women.
Pediatric patients
• Use drug cautiously in neonates. The usual pediatric dosage can be used, but extend dosing intervals.
Geriatric patients
• Elderly and debilitated patients need close observation because they’re more susceptible to drug-induced diuresis. Excessive diuresis promotes rapid dehydration, leading to hypovolemia, hypokalemia, hyponatremia, and circulatory collapse.

Patient education
• Warn patient that photosensitivity reaction may occur. Explain that reaction is a photoallergy in which ultraviolet radiation alters drug structure, causing allergic reactions in some people.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use