First dose hypotension after captopril; can it be predicted? A study of 240 patients.

We have studied prospectively the acute blood pressure lowering effect on an oral dose of captopril, 25 mg in 240 hypertensive patients. The mean relative reduction of systolic and diastolic BP was 16 and 15% respectively and the mean time to the mean arterial pressure nadir was 59 minutes. Systolic BP fell by more than 30% in 4.6% of patients and diastolic BP and mean arterial pressure dropped by more than 30% in 4.2 and 3.3% of patients respectively. Patients over 60 years of age showed a significantly larger fall in systolic and diastolic BP. Patients with renal artery stenosis reached the BP nadir in a significantly shorter time compared with patients with essential hypertension (50.5 vs. 59.7 minutes, P less than 0.05) and showed a significantly larger fall in systolic BP (20.7 vs. 15.4%, P less than 0.05). A forward stepwise regression analysis showed that only baseline plasma renin activity had a significant relation to the fall in BP (P less than 0.01, R = 0.57). We conclude that according to our definition of a greater than 30% decrease of the mean arterial pressure, a first dose hypotension after captopril was seen in 3.3% of 240 patients. Captopril treatment should be introduced carefully since not all those patients at risk of hypotension can be identified in advance.