Torsemide
Torsemide is a long-acting loop diuretic used for heart failure and oedema, and at lower doses for hypertension. It has more reliable oral absorption than furosemide and a longer duration of action, which has supported broader uptake in chronic heart-failure management.
- Chemical formula
- C16H20N4O3S
- CAS number
- 56211-40-6
- ATC code
- C03CA04
- Molecular weight
- 348.42 g/mol
- Drug class
- Loop diuretic
- Also known as
- Demadex, Soaanz, Torem
What is it?
Torsemide is a loop diuretic FDA-approved in 1993, marketed as Demadex (Hoechst Marion Roussel, now Sanofi) and Soaanz, with widely available authorised generics. It is one of three commonly used loop diuretics alongside furosemide and bumetanide. Torsemide has more predictable oral bioavailability and a longer duration of action than furosemide, which has prompted some heart-failure guidelines to consider it preferred over furosemide in chronic congestive heart failure.
Mechanism of action
Torsemide blocks the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, producing potent natriuresis and diuresis. Unlike thiazides, loop diuretics retain efficacy in patients with renal impairment. Torsemide also has additional weak aldosterone-antagonist activity that may contribute to lower potassium loss compared with furosemide at equipotent doses. The diuretic effect develops within an hour of oral dosing.
Pharmacokinetics
Torsemide is well absorbed after oral administration with consistent bioavailability of 80–90% (compared with 50–60% and high variability for furosemide). Onset of diuresis is within 1 hour, peak effect at 1–2 hours, and duration 6–8 hours — markedly longer than furosemide. The terminal half-life is 3.5 hours, supporting once-daily dosing. Hepatic metabolism predominates with about 20% renal excretion unchanged.
Indications
Torsemide is approved for oedema in heart failure, hepatic cirrhosis or chronic kidney disease, and for hypertension at low doses. According to recent heart-failure guidelines, torsemide may be preferred over furosemide for chronic heart-failure management because of its more reliable absorption and the TRANSFORM-HF trial findings, although that trial showed no clear mortality benefit. The dose ratio of torsemide:furosemide is approximately 1:2–4.
Safety profile
Common adverse effects include hypokalaemia, hyponatraemia, hypomagnesaemia, dehydration, hyperuricaemia, hyperglycaemia, ototoxicity (rare, dose-dependent) and orthostatic hypotension. Sulfa allergy is a relative contraindication. Concurrent NSAIDs reduce diuretic efficacy. Serum potassium, sodium, magnesium, renal function and uric acid require periodic monitoring. Orthostatic blood pressure should be checked particularly when starting therapy in older adults.
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Frequently asked questions
Is torsemide better than furosemide for heart failure? ▾
Torsemide has more reliable oral absorption (80–90% bioavailability vs 50–60% and variable for furosemide) and a longer duration of action. The TRANSFORM-HF trial found no clear mortality difference between them for hospitalised heart-failure patients. According to recent heart-failure guidelines, torsemide may be preferred when furosemide absorption is unreliable or when stable diuresis is required.
What lab tests are needed on torsemide? ▾
Serum potassium, sodium, magnesium, renal function and uric acid are checked at baseline, 1–2 weeks after starting or any dose increase, and periodically thereafter. Hypokalaemia and hypomagnesaemia are common and may require oral supplementation, ACE inhibitor combination, or potassium-sparing agents. Glucose, lipids and weight are also tracked, particularly in heart failure.
How does torsemide compare to thiazide diuretics for hypertension? ▾
At low doses (5–10mg daily), torsemide is comparable to thiazides for blood-pressure control with potentially better efficacy in patients with reduced renal function. However, thiazides are generally preferred first-line for uncomplicated hypertension because of greater outcome evidence and lower cost. According to current guidelines, torsemide is more useful when there is concomitant heart failure or significant fluid overload.
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