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.