TORSEMIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
Torsemide inhibits the Na+/K+/2Cl- cotransporter (NKCC2) in the thick ascending limb of the loop of Henle, reducing sodium, chloride, and water reabsorption, leading to increased urine output and decreased extracellular fluid volume.
| Metabolism | Primarily hepatic via CYP2C9 (approximately 80%); minor metabolism by CYP2C8 and CYP2C18; <20% excreted unchanged in urine. |
| Excretion | Approximately 80% renal (20% unchanged, 60% as metabolites, mainly glucuronide conjugate), 20% biliary/fecal. In renal impairment, clearance is reduced and half-life prolonged. |
| Half-life | Terminal elimination half-life is 3-4 hours in healthy adults; prolonged to 4-8 hours in cirrhosis and with advanced age. In renal failure (CrCl <30 mL/min), half-life may exceed 8 hours. |
| Protein binding | Approximately 97-99% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is 0.16-0.25 L/kg. Low Vd indicates limited extravascular distribution; primarily distributes into extracellular fluid. |
| Bioavailability | Oral bioavailability is approximately 80-90%, with no significant food effect. |
| Onset of Action | Oral: 30-60 minutes; IV: within 10 minutes. |
| Duration of Action | Duration of diuresis is 6-8 hours after oral administration; 2-3 hours after IV. Duration may be extended in renal or hepatic impairment. |
Oral or intravenous: 5-20 mg once daily; may titrate up to 40 mg daily. Usual maintenance: 5-10 mg daily.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment for GFR >20 mL/min. For GFR <20 mL/min, use with caution; may require increased dose or more frequent administration. No adjustment in dialysis. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: use with caution; reduce dose by 75% or avoid use. |
| Pediatric use | 0.5-2 mg/kg/dose IV once daily; maximum 4 mg/kg/day. Oral: starting 0.5 mg/kg once daily, titrate to effect. |
| Geriatric use | Start at lower end of dosing range (5 mg daily); monitor renal function and electrolytes; may have increased sensitivity to hypotension and electrolyte disturbances. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other ototoxic drugs may increase risk of hearing loss NSAIDs may reduce the diuretic effect Profound diuresis and electrolyte depletion can occur.
| Breastfeeding | Torsemide is excreted in human milk in low amounts; M/P ratio not established. Use with caution in breastfeeding women due to potential for diuresis and electrolyte disturbances in the infant. The American Academy of Pediatrics considers torsemide compatible with breastfeeding. |
| Teratogenic Risk | Torsemide is a pregnancy category B drug. Animal studies have not shown teratogenicity, but there are no adequate human studies. Use only if clearly needed. First trimester: unlikely risk based on animal data; second and third trimesters: may cause fetal diuresis, electrolyte disturbances, and potential hypovolemia. Avoid in pregnancy-induced hypertension due to risk of decreased placental perfusion. |
■ FDA Black Box Warning
None
| Common Effects | Headache Dizziness Dehydration Constipation Decreased blood pressure Upset stomach |
| Serious Effects |
Anuria, severe hepatic coma or precoma, severe electrolyte depletion, hypersensitivity to torsemide or sulfonamides.
| Precautions | Can cause profound diuresis leading to volume depletion, hypotension, and electrolyte imbalances (especially hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia). May precipitate hepatic encephalopathy in patients with cirrhosis and ascites. Ototoxicity (rare, usually with rapid IV administration or high doses). Monitor renal function and electrolytes. Use caution with sulfonamide allergy (cross-sensitivity possible due to sulfonamide moiety). May exacerbate hyperuricemia and gout. Increased risk of digoxin toxicity due to hypokalemia. |
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| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (especially potassium, sodium, chloride, bicarbonate), renal function (BUN, creatinine), uric acid, blood glucose, and fluid balance. Fetal monitoring: assess fetal growth and amniotic fluid volume with ultrasound, as diuretics may reduce placental perfusion and cause oligohydramnios. |
| Fertility Effects | No specific studies on fertility in humans; animal studies have not shown impairment of fertility. However, chronic use may affect electrolyte balance and hemodynamics, potentially impacting reproductive function indirectly. |