Diuretic activity of torasemide and furosemide in chronic heart failure: A comparative double blind cross-over study

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Abstract
The diuretic effects of torasemide and of furosemide were compared in a double blind cross-over study in 13 patients with stable chronic heart failure. Single doses of 10 mg and 20 mg of torasemide and of 40 mg of furosemide were given orally, in a randomized order on 3 consecutive days. In addition, a placebo was administered on the day preceding the 3 active drug treatment days to obtain control data. Each experimental day was divided into three urine collection periods — 0 to 4 h, 4 to 12 h and 12 to 24 h. Urine output, ion excretion and clearance were measured during each of the 3 periods as well as for the 24-h period. Torasemide 20 mg was distinctly more active in each of the 3 collection periods and in the 24-h period than furosemide 40 mg, whereas no significant difference was found between furosemide 40 mg and torasemide 10 mg for most of the experimental data. From 0 to 4 h, both torasemide and furosemide significantly increased the urinary flow rate and the urinary excretion of sodium, chloride and calcium, while they decreased the urinary osmolality when compared to placebo. All the effects persisted in the 4 to 12 h period after torasemide 20 mg in contrast to furosemide, whose effects were limited to the 0 to 4 h period. In the third period (12–24 h), the urine volume fell below the placebo value after furosemide but not torasemide, and only torasemide 20 mg was followed by a persistent decrease in the urine osmolality. Both diuretics increased the free water clearance, but this phenomenon was slightly greater after torasemide. Finally, urinary potassium excretion was increased by both doses of torasemide and furosemide, with no significant difference between the three experiments. Torasemide and furosemide were well tolerated; no clinical or biochemical adverse effects occurred after administration of either of the compounds. Torasemide is a new loop diuretic which may constitute a good alternative to furosemide in the treatment of oedema in chronic heart failure.