ABSTRACT. Torasemide is a new loop diuretic that combines the effects of furosemide and spironolactone. There are no reports on the effects of torasemide in cats and dogs. This study compared the diuretic effects of furosemide and torasemide in cats and dogs. Cats with pressure overload cardiac hypertrophy were given oral placebo, torasemide 0.3 mg/kg, or furosemide 1 mg/kg or 3 mg/kg. Con trol and mitral regurgitation dogs were given oral placebo, torasemide 0.2 mg/kg, and furosemide 2 mg/kg for 7 days. Urine samples were obtained at baseline and 1, 2,3,4,5,6,8,12, and 24 hr after each drug dose. Urine volume and urine Na + and K + were measured. Both furosemide and torasemide increased urine volume 1 hr after administration. Furosemide caused a dose-dependent increase in urine volume that peaked at 2-3 hr in cats and dogs. The diuretic effect of furosemide disappeared 6 hr after administration, while that of torasemide peaked 2-4 hr after administration and persisted for 12 hr in cats and dogs. In MR dogs, torasemide for 7 days signi ficantly decreased urine potassium excretion. Plasma aldosterone increased with torasemide, whereas there was no change with furosemide. In conclusion, about 1/10 concentration of torasemide was as potent as furosemide and had a longer diuretic effect in cats and dogs . These data suggest that torasemide is useful for treating congestive heart failure or edema in cats and dogs. KEY WORDS: diuretic agent, feline, heart failure, renal function, urine.J. Vet. Med. Sci. 65(10): 1057-1061, 2003 Torasemide is a pyridyl sulfonylurea with a chemical structure between those of loop diuretics and Cl-channel blockers [5,13,20]. The main tubular site of action of torasemide is the ascending limb of the loop of Henle, where it interacts with the Na + , 2Cl -, K + cotransporter localized in the luminal surface [19,20]. Torasemide and furosemide cause a significant, dose-dependant increase in urine flow and the urinary excretion of sodium and potassium [14]. Torasemide has more potent, longer-acting diuretic activity than furosemide [3]. Congestive heart failure, which is characteristically associated with fluid retention and shortness of breath, is a leading cause of morbidity and mortality. Therefore, animals with congestive heart failure require management with diuretics, such as thiazide, bumetanide, and furosemide. Furosemide is the diuretic most frequently given for edema. Although torasemide has beneficial effects in chronic congestive heart failure in humans [8], there are fewer clinical reports than on furosemide. In veterinary medicine, there are no reports on the dose or diuretic effects of torasemide for dogs and cats. Therefore, this study compared the diuretic effects of torasemide and furosemide in dogs and cats. MATERIALS AND METHODSThis study followed the Guidelines for Institutional Laboratory Animal Care and Use of the School of Veterinary Medicine and Animal Science at Kitasato University.Cat study: This study used 8 clinically healthy domestic short hair cats (4 males, 4 fem...

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