The Effects of the Loop Diuretics Furosemide and Torasemide on Diuresis in Dogs and Cats

Abstract

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...

Aldosterone receptor antagonists - how cardiovascular actions may explain their beneficial effects in heart failure

“…In humans, in terms of mineralocorticoid effects, 25 mg spironolactone is approximately equivalent to 50 mg eplerenone (Kalidindi et al, 2007) is a loop diuretic (Hori et al, 2007), registered in human medicine, which also appears to have a potassium sparing diuretic action, presumably through the antagonism of aldosterone. In the dog, however, although the diuretic actions of torasemide have been demonstrated (Uechi et al, 2003), the precise mode of its potassium sparing diuretic effect has not been clearly characterized in the published literature. This agent will not be considered further in the present review.…”

Torsemide Versus Furosemide After Continuous Renal Replacement Therapy Due to Acute Renal Failure in Cardiac Surgery Patients

“…[15] In animal experiments and one study done with CHF patients, an increase of aldosterone was found after loop diuretic therapy. [10,11,13,14] In in vitro, animal, and human studies in CHF patients, torsemide inhibited aldosterone binding to the receptor, causing an anti-aldosteronic effect with reduced kaliuresis. [10 -14,24] The accurate potassium substitution performed in this study could have influenced aldosterone levels, as aldosterone secretion is dependent on potassium levels.…”

Application of torsemide to two dogs with congestive heart failure

“…In this case series, we selected the application of torsemide as a replacement for furosemide to diminish the fluid accumulation caused by CHF, and found that it mitigates clinical sign such as pulmonary edema for a long period of time. Although the expected effects of loop diuretics, including hyponatremia, hypokalemia, hypochloremia, decreased urine specific gravity, and increased BUN and creatinine were observed [13], the quality of life for patients with CHF is also maintained well in these cases. The combination of furosemide and hydrochlorothiazide appears to be effective at combating refractory pulmonary edema, although clinicians must be aware of electrolyte abnormalities including hypokalemia [10].…”

“…Torsemide, like furosemide inhibits Na − cotransport system [13]. Torsemide has a greater and more regular bioavailability, longer half-life, and longer duration of action than furosemide.…”

“…The bioavailability of torsemide is about 80~100% compared to 10~100% for furosemide, its half-life after oral administration is about 8 h, which is longer than furosemide, and its duration of action is approximately twice that of furosemide (12 h vs. 6 h). In dogs with congestive heart failure, to produce diuresis and urinary sodium excretion equivalent to that in humans, the torsemide dose is 1/10 the dose of furosemide, whereas increased potassium excretion is less common [13]. We applied torsemide (0.3 mg/kg q12 h) at a 1/10 of the dose of furosemide in the present study.…”