Dose-dependent inhibition of angiotensin converting enzyme by enalapril in cats.

Although heart failure in cats is treated with angiotensin converting enzyme (ACE) inhibitors, data on the effects of different doses of enalapril on hemodynamics and the inhibition of ACE activity have not been published. To evaluate the effect of enalapril, 0.25, 0.5, or 1.0 mg/kg was given once (s.i.d., p.o.) or twice (b.i.d., p.o.) a day, and plasma ACE activity, indirect blood pressure, and heart rate were measured. Plasma ACE activity and blood pressure fell dose-dependently. There was a biphasic effect on blood pressure with twice daily administration. Enalapril 0.25 mg/kg b.i.d. inhibited plasma ACE activity by 40% after 24 hr, which was almost the same as the effect of 0.5 and 1.0 mg/kg s.i.d., and 0.5 and 1.0 mg/kg b.i.d., while 0.25 mg/kg s.i.d. inhibited it by 23%. Thus, enalapril with a daily dose exceeding 0.5 mg/kg may provide similar efficacy of ACE inhibition in cats.