Benazepril-d is intended for use as an internal standard for the quantification of benazepril . Benazepril is a prodrug of the angiotensin converting enzyme (ACE) inhibitor benazeprilat . It is metabolized to benazeprilat by hepatic esterases. Benazepril inhibits the in vitro enzymatic activity of partially purified ACE isolated from rabbit lung (IC = 2 nM). It decreases the triglyceride and total cholesterol levels in normotensive rats when administered at a dose of 30 mg/kg and decreases aortic atherosclerosis in cholesterol-fed rabbits when administered at a dose of 3 mg/kg per day. Benazepril (0.1-10 mg/kg per day) reduces blood pressure in spontaneously hypertensive rats. It also decreases proteinuria in cats with chronic kidney disease when administered at doses ranging from 0.5 to 1 mg/kg per day. Formulations containing benazepril have been used to treat hypertension, congestive heart failure, and chronic kidney disease in both human and veterinary medicine.