Captopril--nifedipine interaction in hypertension.

Nifedipine, a calcium channel blocker exerts significant peripheral vasodilatory activity in hypertensive patients. It has been postulated that the antihypertensive effect of peripherally acting vasodilators is masked, by counter regulatory mechanism e.g. activation of renin-angiotensin aldosterone (RAA) axis. The present work was undertaken to study the effect of blockade of RAA axis using captopril, an angiotensin converting enzyme inhibitor on the blood pressure lowering activity of nifedipine. Pretreatment with captopril in a dose of 25 mg. bd was carried out for 4 weeks in one group of 10 patients before administering nifedipine 10 mg bd for 4 weeks. The other matched group of 10 patients received nifedipine alone in the same dose. It was observed that although captopril by itself had no appreciable effect on blood pressure in the dose used, it significantly enhanced the blood pressure lowering activity of nifedipine. It appears that counterregulatory mechanisms play an important role in determining the net antihypertensive effect of peripheral vasodilators.