Dose response in captopril therapy of hypertension.

Dose-response curves of blood pressure and of the biochemical components of the renin-angiotensin-aldosterone system were determined during long-term treatment with captopril in 21 hypertensive patients. Captopril was given in biweekly, doubling doses starting with 25 mg 3 times a day until control of blood pressure was achieved or a total daily dosage of 600 mg was reached. Recumbent and standing systolic and diastolic blood pressure fell on 75 mg captopril daily. Increasing the captopril dose did not induce further significant hypotensive effects. The pretreatment level of plasma renin activity (PRA) was a poor predictor of the hypotensive effect of captopril. The rises in PRA and plasma angiotensin I level (PA I) and the decrease in plasma angiotensin II level (PA II) and plasma aldosterone level (PAC) provide biochemical evidence for angiotensin-converting enzyme (ACE) inhibition in vivo. These effects were present on daily doses of 75 to 150 mg captopril.