Anti-hypertensive effects of intravenous compared with oral captopril

Twenty mild to moderate hypertensive subjects (11 men, 9 women, mean age 54.3 years, range 39-65 years) were studied to determine whether an intravenous form of captopril could be as safe and efficacious as an oral form and to estimate the time course of anti-hypertensive action over a wide dose range (100-fold) of i.v. doses versus oral captopril and placebo. Each subject demonstrated supine diastolic blood pressure (DBP) < or = 90 mm Hg following prospective ACE inhibitor monotherapy, with return of supine DBP to within 95-110 mm Hg 4 weeks after ACE inhibitor discontinuation. These subjects were then admitted to an inpatient unit for six 24 h periods; an initial acclimation period followed by five single doses of i.v. captopril (1.25, 12.5 and 125 mg) or placebo given as a 20 min infusion and oral captopril (25 mg) or placebo in a double-blind, double-dummy crossover study. Each dose was separated by 48 h. All 20 patients completed the study with no clinically significant adverse events. Captopril at doses of 125 mg i.v., 12.5 mg i.v. and 25 mg orally produced similar BP reductions over the 12 h postdose interval, and were more effective in lowering BP than intravenous captopril 1.25 mg or placebo. The 125 mg intravenous captopril dose was no more effective overall in BP reduction than the 12.5 mg i.v. and 25 mg oral doses and was associated with a greater incidence of adverse events. Treatment with 12.5 mg i.v. captopril is safe and comparable to 25 mg oral therapy.