Effects of the angiotensin converting enzyme inhibitor, captopril, in essential hypertension.

1 The effects of the orally active angiotensin converting enzyme inhibitor, captopril, were examined in 15 patients with mild or moderate essential hypertension. 2 Following initial dosing with captopril 25 mg, there was a significant fall in supine and erect blood pressure in 2 h and lasting for 6 h. There was no significant alteration of heart rate. No reduction was seen in plasma noradrenaline concentration. Maximum inhibition of plasma converting enzyme activity occurred 60 min post-dosing. 3 There was a strong positive correlation between blood pressure reduction and converting enzyme inhibition. The magnitude of the blood pressure reduction and converting enzyme inhibition following initial dosing was reflected in subsequent success with captopril monotherapy during a 12 week follow-up period. 4 It was also found that patients who did not achieve adequate blood pressure control on captopril in doses of 50 mg three times daily or less still were not controlled on a dose of 150 mg three times daily without the addition of a diuretic. 5 The risks of renal and marrow toxicity from captopril may be reduced by administering only low doses with the addition, where necessary, of a thiazide diuretic.