How spironolactone affects urine and water output in healthy dogs

Abstract

OBJECTIVES: To document the diuretic effect of different oral doses of spironolactone (SP) in healthy dogs. BACKGROUND: SP is currently mentioned as a diuretic agent in the dog. However, the recommended doses were empirically defined and their corresponding diuretic effect has never been documented in dogs. ANIMALS, MATERIALS AND METHODS: Eight adult Beagle dogs were used for two separate 2*2 cross-over designs. In the first cross-over, 4 dogs received SP orally for 8 days at 1 and 2mg/kg per day. In the second cross-over the 4 other dogs received SP similarly, but at 4 and 8 mg/kg per day. Dogs were weighed on the first and last day of each period. Plasma SP and canrenone (the main active metabolite of SP) were assayed by high performance liquid chromatography (HPLC). Daily water consumption, urine weight, urine specific gravity, and urine excretion of sodium and potassium were measured during the SP treatment. RESULTS: Two hours after SP administration, SP was metabolized into canrenone. A significant 14 and 22% decrease in urine potassium excretion was observed at 1 and 2mg/kg, respectively, but not at the two other dose levels. Daily water consumption, urine weight, urine specific gravity, and urine excretion of sodium were not significantly altered by the SP treatment regardless of dose. CONCLUSIONS: Repeated oral administration of SP at 1, 2, 4 or 8 mg/kg for 8 days had no effect on water and sodium diuresis in healthy dogs.