Enalapril & nifedipine in essential hypertension; synergism of the hypotensive effects in combination.

Twelve male hypertensive patients who had required enalapril and nifedipine to control their blood pressure were entered into a study of modified 2 x 2 factorial design (3 week study periods) to determine the effect of each drug separately and in combination. Factorial analysis indicated that enalapril alone (20 mg/d) lowered supine blood pressure by 10 +/- 2/8 +/- 1 mmHg, nifedipine alone (30 mg/d) lowered supine blood pressure by 11 +/- 2/8 +/- 1 mmHg and there was a positive interactive effect of 10 +/- 3/7 +/- 2 mmHg (P less than 0.001) such that the combination lowered supine blood pressure by 32 +/- 3/24 +/- 2 mmHg. The effects of the individual drugs were both significant (P less than 0.001) but did not differ from each other. Enalapril and nifedipine are both effective antihypertensive drugs and in some hypertensive patients their effects appear to be synergistic.