BACKGROUND: The effects of sacubitril/valsartan (S/V) on the 
renin-angiotensin-aldosterone system (RAAS) in dogs with cardiomegaly secondary 
to myxomatous mitral valve disease (MMVD) are currently unknown.
OBJECTIVES: To determine the pharmacodynamic effects of S/V on the RAAS, 
natriuretic peptide concentrations, systolic arterial pressure (SAP), tests of 
renal function, and serum electrolyte concentrations in dogs with cardiomegaly 
secondary to MMVD.
ANIMALS: Thirteen client-owned dogs weighing 4-15 kg with American College of 
Veterinary Internal Medicine (ACVIM) Stage B2 MMVD.
METHODS: Prospective, randomized, double-blind, placebo-controlled pilot study 
of S/V in dogs with ACVIM Stage B2 MMVD.
RESULTS: Thirteen dogs were recruited: S/V (n = 7) and placebo (n = 6). The 
median percentage increase in urinary aldosterone to creatinine ratio (UAldo : 
C) between day 0 and day 30 was significantly lower in the S/V group (12%; 
P = .032) as compared with the placebo group (195%). The median percentage 
decrease of NT-proBNP concentration from day 0 to day 30 was not statistically 
different between groups (P = .68). No statistical differences were seen in 
echocardiographic, thoracic radiographic, SAP, or serum biochemical test results 
measured at any time point between groups. No adverse events were observed for 
dogs in either group.
CONCLUSION AND CLINICAL IMPORTANCE: Sacubitril/valsartan may provide a new 
pharmaceutical method to effectively inhibit the RAAS in dogs with ACVIM Stage 
B2 MMVD.