Tolvaptan substitution for torsemide is associated with improved renal biomarkers in dogs with advanced myxomatous mitral valve disease and concurrent azotemia.

Replacing torsemide with tolvaptan significantly improved renal biomarkers in azotemic dogs with advanced MMVD.

This retrospective observational study investigated the safety and preliminary efficacy of substituting torsemide (a loop diuretic) with tolvaptan (a vasopressin V2 receptor antagonist/aquaretic) in 41 dogs with ACVIM stage C or D myxomatous mitral valve disease (MMVD) complicated by concurrent azotemia. Dogs were divided into three 60-day cohorts: group 1 received a 25–50% torsemide dose reduction, group 2 had 50% of torsemide replaced with tolvaptan, and group 3 underwent complete torsemide-to-tolvaptan substitution. Renal biomarkers (BUN, creatinine, SDMA) were measured at baseline, day 30, and day 60. Groups 2 and 3 demonstrated statistically significant reductions in all three renal biomarkers at both time points compared to baseline. In group 2, mean creatinine declined from 2.4 mg/dL to approximately 1.6–1.7 mg/dL, and SDMA decreased from 29.9 to roughly 21.5–23.6 µg/dL. Group 1 (torsemide reduction alone) showed no significant improvement. Modest hypernatremia was noted in tolvaptan groups, but potassium remained within reference ranges. Echocardiographic indices and hepatic parameters were stable throughout, suggesting maintained cardiac efficacy and no hepatotoxicity. The authors conclude that tolvaptan substitution may offer a viable strategy to mitigate loop diuretic-induced renal impairment in dogs with congestive heart failure, while preserving fluid management goals. However, the retrospective design, small sample sizes per group, and absence of a randomized control group necessitate prospective, controlled trials to validate these findings and establish definitive clinical recommendations.

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