Loop Diuretics: Furosemide
Indication
Furosemide is most commonly used in the management of edema during congestive heart failure and hepatic or renal disease. Frequently, it is the diuretic of choice to treat postoperative edema after cardiac surgery. It may also be used in the treatment of hypertensive patients1 alone or in combination with other antihypertensive medications.
Mechanism of Action
Furosemide is a loop diuretic and functions through inhibition of reabsorption of sodium and chloride from the ascending loop of Henle. It interferes with the chloride-binding cotransport system (Na+-K+-2C1~ symporter) and halts salt transport in this segment. This action causes increased excretion of water, sodium, chloride, and potassium. The drug also inhibits calcium and magnesium reabsorption in the ascending limb by eliminating the transepithelial potential difference.
Dosing
Neonates, premature:
Oral (poor bio availability): doses of 1 to 4mg/kg/dose once or twice daily have been used
Intramuscular (I.M.), intravenous (I.V.): 0.25 to 2mg/kg/dose administered every 12 to 24 hours
Infants and children:
Oral: 1 to 6 mg/kg/day divided every 6 to 12 hours
I.M., I.V.: 0.25 to 2mg/kg/dose every 6 to 12 hours
I.V. continuous infusion: 0.05mg/kg/h initially, titrate to clinical effect. Usual dosage range, 0.1 to 0.4mg/kg/h.
Adults:
Oral: initial, 20 to 80 mg/dose; increase in increments of 20 to 40mg/dose at intervals of 6 to 8 hours; usual maintenance dose interval is once or twice daily; may be titrated up to 600 mg/day for severe edematous states
I.M., I.V.: 20 to 40mg/dose; repeat in 1 to 2 hours as needed and increase by 20 mg/dose until the desired effect has been obtained; usual dosing interval, 6 to 12 hours; for acute pulmonary edema, the usual dose is 40 mg I.V.; if not adequate, may increase dose to 80 mg
Continuous I. V. infusion: initial I.V. bolus dose of 20 to 40 mg followed by continuous I.V. infusion doses of 0.l mg/kg/h doubled every 2 hours to a maximum of 0.4 mg/kg/h
Pharmacokinetics
The onset of action of furosemide after oral administration is 30 to 60 minutes after administration. The peak effects occur within 1 to 2 hours and the duration of action is 6 to 8 hours. After I.V. injection, diuresis begins after 5 minutes and lasts for 2 hours. After oral dosing, 45 to 65% of the drug is absorbed and the protein binding is 98%. The hepatic metabolism of the drug is minimal and the half-life is approximately 30 minutes.
Monitoring parameters:
serum electrolytes (sodium, potassium, chloride, and bicarbonate), renal function (blood urea nitrogen [blood urea nitrogen] and creatinine [Cr]),blood pressure
Contraindications:
Anuria
Precautions/Adverse Effects
Warning: loop diuretics are potent agents. Excess amounts may lead to profound diuresis with fluid and electrolyte loss. Close medical supervision and dose evaluation is required.
Adverse effects of furosemide use include serious depletion of total body Na+ manifesting in hyponatremia or extracellular fluid volume depletion associated with hypotension, reduced glomerular filtration rate, or circulatory collapse. Also reported are dizziness, urticaria,hypokalemia, nausea, pancreatitis, headaches, photosensitivity, diarrhea, dehydration, and anemia. Ototoxicity is possible, as is appearance of the Sweet syndrome. Other effects may include hypochloremia, metabolic alkalosis, hypercalciuria, agranulocytosis, thrombo-cytopenia, nephrocalcinosis, prerenal azotemia, hyperuricemia, and interstitial nephritis. Oral solutions contain sorbitol, which may cause diarrhea.
Drug-Drug Interactions
Nonsteroidal anti-inflammatory drugs (NSAIDs) decrease the effect of furosemide. There is increased ototoxicity with aminoglycosides and ethacrynic acid; and drugs affected by potassium depletion, such as digoxin. There is increased anticoagulation by warfarin; decreased glucose tolerance may increase requirements of oral antidiabetic agents; and there is decreased lithium excretion with furosemide administration.
Poisoning Information
Symptoms of furosemide overdose may include weakness, muscle cramps, fatigue, dizziness, fainting, confusion, irregular pulse, dry mouth, dehydration, nausea, and vomiting. Decontamination using activated charcoal is recommended and other treatment is supportive and symptomatic.
Compatible Diluents/Administration
Injection can be administered undiluted or can be diluted in normal saline or 5% dextrose in water (D5W) to a concentration of 1 to 2mg/mL and will be stable for 24 hours at room temperature. Administration is by direct I.V. injection at a maximum rate of 0.5mg/kg/min.
This post has been viewed 591 times.
Comments are closed.
