A study of the antihypertensive effect and some pharmacodynamic aspects of nifedipine in medium-term treatment.

The antihypertensive activity of nifedipine in medium-term treatment has been studied in 30 patients affected by II and III WHO grade essential hypertension. After a 6-day period of placebo, patients were randomly allotted to group A (treated with single 10-mg doses of nifedipine) and group B (treated with single 20-mg doses). Treatment with nifedipine continued for 18 days. Patients in both groups were given one daily dose during the first 6 days, two daily doses in the following 6 days and three daily doses in the last 6 days. 1. Antihypertensive effect: In both groups, only three daily doses gave a satisfactory 24-hour antihypertensive activity. Nifedipine as monotherapy administered in single doses of both 10 mg (group A) and 20 mg (group B) normalized blood pressure (BP) and the measured antihypertensive effect was not statistically different in the two groups. The antihypertensive effect lasted between 7 and 8 hours after drug administration (both doses) and did not diminish with increasing duration of treatment or number of daily doses. 2. Change in heart rate: Nifedipine induced an increase in HR which diminished with shortening of the time interval between daily administrations. The effect on HR was unaltered throughout the whole experimental period. 3. Side-effects: Nifedipine did not induce orthostatic hypotension in any patient. Eleven of the 30 patients complained of side-effects, the most common being headache and palpitations. Incidence and severity of side-effects were not correlated with dose, whereas duration was longer with 20 mg. Side-effects never necessitated withdrawal of the drug.