Clinical and hemodynamic experience with enalapril in congestive heart failure.

The renin-angiotension system is activated in many patients with congestive heart failure (CHF), resulting in angiotensin-mediated vasoconstriction and aldosterone-mediated sodium and water retention. To evaluate the effectiveness of enalapril, a new converting enzyme inhibitor, enalapril was administered to patients either orally or intravenously in a single dose, and hemodynamic and hormonal responses were measured. Patients were then placed on oral enalapril therapy for 1 month, and treadmill exercise duration and invasive hemodynamics were compared with baseline pretreatment data. With single-dose administration, both oral and intravenous enalapril reduced systemic vascular resistance and increased cardiac output. However, the effects of oral enalapril were not manifest for 3 to 4 hours, because oral enalapril is a pro-drug form that requires hepatic deesterification. In contrast, intravenous enalapril resulted in significant hemodynamic and hormonal changes 15 to 30 minutes after administration. During long-term therapy, enalapril was associated with improved symptomatology, increase of treadmill exercise duration and sustained hemodynamic improvement. Enalapril was effective therapy for chronic CHF. Optimal short-term response may require coadministration of both intravenous and oral preparations of enalapril; however, the magnitude of the short-term response was comparable for both preparations. Long-term therapy is most effective when the drug is administered as a twice-daily regimen.