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. |
| Molecular Weight | 348.42 |
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 | Avoid unless clearly needed; use only if benefit outweighs risk. Animal studies show fetotoxicity. |
| 2nd trimester | May cause fetal hypovolemia and electrolyte disturbances; use only if clearly indicated. |
| 3rd trimester | May cause fetal hypovolemia, electrolyte imbalances, and possible neonatal diuresis; avoid due to risk of oligohydramnios. |
Clinical note
Other ototoxic drugs may increase risk of hearing loss NSAIDs may reduce the diuretic effect Profound diuresis and electrolyte depletion can occur.
| Placental transfer | Crosses placenta; demonstrated in animal studies and human data suggest transfer. |
| Breastfeeding | Excreted into breast milk in low amounts; consider risk of dehydration and electrolyte imbalance in infant. Monitor infant for diuretic effects. |
■ FDA Black Box Warning
None
| Common Effects | Headache Dizziness Dehydration Constipation Decreased blood pressure Upset stomach |
| Serious Effects |
AnuriaHypersensitivity to torsemide or sulfonylureasSevere hepatic encephalopathySevere hypovolemia or dehydration
| 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. |
| Food/Dietary |
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| Lactation Rating |
| L3 (Moderately Safe) |
| 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. |
| 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. |
| High salt intake reduces diuretic efficacy; advise a low-sodium diet. Food may slightly delay absorption but does not significantly alter bioavailability. Grapefruit juice has no known interaction. Avoid excessive potassium intake (e.g., potassium supplements, salt substitutes) unless directed by physician. |
| Clinical Pearls | Torsemide is a loop diuretic with high bioavailability (80-100%) and a longer half-life (3-4 hours) than furosemide; it is less affected by food intake. Monitor for ototoxicity with rapid IV administration or high doses, especially in renal impairment. Use caution in patients with sulfonamide allergy (cross-reactivity possible). Torsemide may cause hyperuricemia and gout attacks. In heart failure, it reduces mortality compared to furosemide in some studies. Hypokalemia risk is dose-dependent; consider potassium-sparing diuretic co-administration. |
| Patient Advice | Take torsemide exactly as prescribed; do not skip doses or double up. · Take the dose in the morning to avoid nighttime urination. · Avoid alcohol and NSAIDs (like ibuprofen) as they may reduce effectiveness and increase kidney risk. · Report symptoms of fluid/electrolyte imbalance: severe dizziness, fainting, irregular heartbeat, muscle cramps, or weakness. · Monitor blood pressure regularly and keep a log. · Weigh yourself daily and report rapid weight gain or loss. · Do not stop taking without consulting your doctor; sudden withdrawal can worsen heart failure. · Torsemide can cause dizziness or lightheadedness; avoid driving or hazardous activities until you know how it affects you. · Use sunscreen and protective clothing; torsemide may increase sun sensitivity. |