Effect of benazepril and pimobendan on serum angiotensin-converting enzyme activity in dogs.

To support their combined use, the objective of the study was to evaluate the effects of benazepril and pimobendan on serum angiotensin-converting enzyme (ACE) activity in dogs. A total of 48 healthy beagle dogs were randomized into four groups (n = 12 per group) in a parallel-group design study: A (control, placebo twice daily (BID)); B (0.5-1.0 mg/kg benazepril once daily (SID) in the morning, placebo in the evening); C (0.25-0.5 mg/kg benazepril BID); D (0.25-0.5 mg/kg benazepril and 0.125-0.25 mg/kg pimobendan, both BID). The test items were administered orally for 15 days. Serum ACE activity was measured on days 1 and 15. Groups B, C and D had significantly lower average serum ACE activity compared to baseline and to the control group, on both days 1 and 15. There were no significant differences in average ACE activity between groups B, C and D. Noninferiority of group C to B was demonstrated. In conclusion, 0.25-0.5 mg/kg benazepril administered BID produced noninferior inhibition of serum ACE activity compared to 0.5-1.0 mg/kg benazepril dosed SID. Pimobendan had no significant effect on benazepril's action on serum ACE activity. The results support the use of benazepril BID in dogs and in combination with pimobendan.