Pharmacokinetics, Safety, and Pharmacologic Effects of Fosinopril Sodium, an Angiotensin‐Converting Enzyme Inhibitor in Healthy Subjects

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Abstract
The pharmacokinetics, pharmacodynamics, and safety of fosinopril sodium (SQ 28,555), a new orally active angiotensin‐converting enzyme (ACE) inhibitor, was evaluated in 73 healthy men in two separate studies. In study I, doses ranging from 10 to 640 mg were administered once daily for 3 days to seven groups of five subjects each. Serum aldosterone levels, ACE activity, and sitting blood pressure were determined, as were pharmacokinetic parameters of fosinoprilat, the active diacid of fosinopril. In a dose‐tolerance study (study II), 80 and 160 mg of the drug were administered in doses of 40 mg bid and 80 mg bid for 2 weeks. Pharmacokinetics were determined on days 1 and 14, and blood pressure and ACE activity were measured daily. One hour after all doses of fosinopril, serum ACE activity was undetectable. Peak blood levels of fosinoprilat occurred at about 3 hours after dosing, and linear kinetics of the diacid were observed. ACE activity remained undetectable for more than 24 hours after the treatment was stopped in study II. Serum aldosterone levels were decreased by 50% of baseline values in both studies. In study I, maximal reductions in mean blood pressure occurred approximately 6 hours postdose; once‐daily doses of 20 mg or greater achieved reductions of 11.3 to 21.6% (P < .05, compared with placebo reductions). Fosinopril was well tolerated. Subjects reported only mild gastrointestinal complications at doses of 80 mg/day or higher. These data show that fosinopril is a safe and effective inhibitor of ACE with a long duration of action on serum ACE activity.