Comparison of the diuretic effect of furosemide by different methods of administration in healthy dogs

OBJECTIVE: To compare the diuretic effects of subcutaneous (s.c.) administration of furosemide to conventional methods of administration including intravenous (i.v.), per os (p.o.), and constant rate infusion (CRI) in healthy dogs. DESIGN: Prospective, randomized, cross-over study. SETTING: Veterinary university research facility. ANIMALS: Seven healthy, adult mongrel dogs (3 males, 4 females). INTERVENTION: Each dog in the study was randomly assigned to receive a 2 mg/kg dose of furosemide via a single s.c., i.v., or p.o. dose at the beginning (time 0) of an 8-hour study, or via CRI during an 8-hour study period. Urine was collected by emptying the bladder using an indwelling catheter and blood samples were obtained via venipuncture at time 0 for baseline measurements and at 1, 2, 4, 6, and 8 hours into the study. Hourly urine output was calculated in all dogs for each study. Complete blood count, plasma total protein, blood urea nitrogen, creatinine, and renin concentration were measured for each sample. MEASUREMENTS AND MAIN RESULTS: The s.c. administration of furosemide resulted in a urine output per hour (UOP/h) that peaked at 1 hour with UOP/h returning to baseline at 4 hours after injection. Following i.v. administration, UOP/h also peaked at 1 hour but returned more rapidly to baseline levels at 2 hours after injection. With p.o. administration, UOP/h reached a maximum UOP/h at 2 hours but time to return to baseline levels was prolonged to 6 hours after administration. With CRI administration, the time to the maximum UOP/h was delayed to 4 hours after injection but UOP/h was then maintained throughout the study period. CONCLUSIONS: Total urine output following s.c. administration of furosemide in healthy dogs was similar when compared to the i.v. and p.o. route. Subcutaneous route may be an effective means for administration of furosemide in dogs, particularly when i.v. access is difficult.