Furosemide, Torasemide (Efficacy)

Both furosemide and torasemide are loop diuretics from the sulfonamide group. Both block the transport system Na+ K+ 2Cl- but while furosemide acts on the descending branch of the loop of Henle, torasemide does so in the ascending branch. Both increase the excretion of Na, K, Ca and Mg.

CONTRAINDICATIONS

• Furasemide: Hypersensitivity to furosemide or sulfonamides. Hypovolemia or dehydration, anuric renal failure, hypokalemia or severe hyponatremia. Precomatose and comatose state associated with hepatic encephalopathy.
• Torasemide: Hypersensitivity to torasemide or sulfonylureas. Anuria.

SIDE EFFECTS

• Furasemide: Electrolyte alterations, dehydration and hypovolemia, elevated blood levels of creatinine and triglycerides. Increased urine volume, hypotension including orthostatic hypotension (especially after intravenous infusion) with hemoconcentration.

Hepatic encephalopathy in patients with hepatocellular insufficiency.

• Torasemide: Dizziness, headache, nausea, weakness, vomiting; hyperglycemia, excessive urination, hyperuricemia, hypokalemia, excessive thirst, hypovolemia, impotence, dyspepsia. In addition, with prolonged release forms of torasemide: drowsiness; diarrhea; increase in urination frequency, polyuria, nocturia.

PHARMACOLOGIC INTERACTIONS

• Furasemide: The effect of furosemide is diminished by concomitant treatment with sucralfate, NSAIDs (non-steroidal anti-inflammatory drugs), salicylates, phenytoin, probenecid, methotrexate and other drugs with significant renal tubular secretion.

Furasemide potentiates the ototoxicity of aminoglycosides, cisplatin and other ototoxic drugs. Also increases the nephrotoxicity potency of nephrotoxic antibiotics and cisplatin.

Furasemide decreases the effect of antidiabetics and increases the toxicity of lithium, digitalis drugs and drugs that prolong the QT cardiac interval.

• Torasemide: Torasemide increases the toxicity of salicylates.

The effect of torasemide can be inhibited by: indomethacin and probenecid.

Reduced oral absorption by cholestyramine.

BRAND NAMES

• Furosemide: Seguril ®
• Torasemide: Sutril®, Dilutol®, Isodiur®