Fosinopril-d7 is intended for use as an internal standard for the quantification of fosinopril by GC- or LC-MS. Fosinopril is a prodrug form of the angiotensin-converting enzyme inhibitor fosinoprilat. Oral administration of fosinopril inhibits angiotensin I-induced pressor responses in normotensive rats, dogs, and monkeys when administered at doses of 15, 15, and 10 µmol kg, respectively. Fosinopril reduces fractional shortening and decreases left ventricular size in a porcine model of congestive heart failure. Formulations containing fosinopril have been used in the treatment of hypertension and congestive heart failure.