Effect of intense angiotensin II suppression on the diuretic response to furosemide during chronic ACE inhibition

Abstract

Background: Contrary to expectation, most studies have demonstrated that initiation of an angiotensin-converting enzyme (ACE) inhibitor in conventional doses in patients with heart failure reduces the diuretic efficacy of furosemide. Recently, it has been suggested that single low doses (1 mg) but not high doses (25 mg) of captopril enhance furosemide-induced diuresis. It is not known whether the interaction between diuretics and ACE inhibitors are altered during long-term dosing. Methods and Results: Eight patients with heart failure treated with diuretics and ACE inhibitors for at least 3 months were studied. All patients were established on captopril 12.5 mg three times daily for 2 weeks before the study. Sodium intake was fixed before the study, and usual medication was withheld on study days. Intravenous furosemide was given on each of 2 study days to maintain a moderate, constant diuresis. Renal plasma flow and glomerular filtration rate (GFR) were determined using clearance techniques, and urine was collected hourly over 4 hours. Captopril 12.5 mg or placebo was given in a randomized, single-blind fashion at the end of the first hour. Compared with placebo, captopril reduced plasma concentrations of angiotensin II (23±18 versus 4±3 pg/mL 1 hour after dosing, P