Torasemide. A review of its pharmacological properties and therapeutic potential

Torasemide (torsemide) is a high-ceiling loop diuretic which acts on the thick ascending limb of the loop of Henle to promote rapid and marked excretion of water, sodium and chloride. Like furosemide (frusemide), its major site of action is from the luminal side of the cell. Torasemide is at least twice as potent as furosemide on a weight-for-weight basis, produces equivalent diuresis and natriuresis at lower urinary concentrations and has a longer duration of action, allowing once-daily administration without the paradoxical antidiuresis seen with furosemide. Torasemide also appears to promote excretion of potassium and calcium to a lesser extent than furosemide. In trials of up to 48 weeks' duration in patients with mild to moderate essential hypertension, torasemide, administered as a single daily dose, has been shown to achieve adequate blood pressure control reaching steady-state within 8 to 12 weeks. Those patients not responding initially have generally responded to a doubling of the dose. Comparative trials of up to 6 months show torasemide is as effective as indapamide, hydrochlorothiazide or a combination of triamterene/hydrochlorothiazide in maintaining control of blood pressure. Torasemide has also been used successfully to treat oedematous states associated with chronic congestive heart failure, renal disease and hepatic cirrhosis. In short term trials control of blood pressure, bodyweight and residual oedema has been sustained. Torasemide appears to be a useful alternative to furosemide in these patients, providing potent and long-lasting diuresis while being relatively potassium and calcium sparing. In clinical trials to date torasemide has been well tolerated with adverse effects of a mild, transient nature reported by only small numbers of patients. Changes in biochemical parameters have been common, including decreases in plasma sodium and potassium levels and increases in plasma creatinine and uric acid levels. These changes are typical of loop diuretics. No changes were clinically significant nor were clinically relevant changes noted in glucose metabolism, cholesterol or triglyceride levels or in haematological values. Thus, torasemide is an interesting new loop diuretic with potential use in the treatment of mild to moderate essential hypertension and of oedematous states in which diuretic therapy is warranted. Preliminary studies suggest it to be as efficacious as other diuretics in common use and to have some advantage over furosemide in duration of action and in effects on potassium and calcium. However, further long term trials in larger groups of patients are needed to delineate the place of torasemide in therapy fully, both as a single agent and in combination with other currently accepted drug regimens.