Design and analysis of the HYPREN-trial: safety of enalapril and prazosin in the initial treatment phase of patients with congestive heart failure.

Since the introduction of angiotensin converting enzyme (ACE) inhibitors into the adjunctive treatment of patients with congestive heart failure, cases of severe hypotension, especially on the first day of treatment, have occasionally been reported. To assess the safety of the ACE inhibitor enalapril a multicenter, randomized, prazosin-controlled trial was designed that compared the incidence and severity of symptomatic hypotension on the first day of treatment. Trial medication was 2.5 mg enalapril or 0.5 prazosin. Subjects were 1210 inpatients with New York Heart Association (NYHA) functional class II and III. Patients who received enalapril experienced clinically and statistically significantly less symptomatic hypotension (5.2%) than the patients who received prazosin (12.9%). All patients recovered. It was concluded that treatment with enalapril was well tolerated and it is, therefore, unreasonable to restrict the initiation of treatment with enalapril to inpatients.