Dose response and length of action of nifedipine capsules and tablets in patients with essential hypertension: a randomised crossover study.

Twelve patients with essential hypertension on no other drug treatment were entered into a randomised crossover study of 5, 10 and 20 mg capsules of nifedipine given 3 times a day and 20 mg tablets given twice a day. Each dose was given for 2 weeks in a random order. All forms of nifedipine were effective in lowering blood pressure. However, 5 mg capsules were less effective than the 10 and 20 mg capsules or 20 mg tablets. There was little to choose between the latter. All doses of nifedipine were more effective 1 and 3 h after the dose compared to subsequent times afterwards. Indeed, as time elapsed after the last dose up to 12 h, there was a gradual increase in blood pressure. However, even at 12 h the 10, 20 mg capsules and 20 mg tablets were still causing an approximate 10% reduction in blood pressure. Nifedipine tablets are as effective as capsules though they might be longer acting, particularly around 6 h after the last dose.