The correlation between the hypotensive effect of increasing single doses of nifedipine tablets with its plasma concentration in patients with essential hypertension.

The hypotensive effect and the plasma concentration following 20, 40, 60 and 80 mg single doses of nifedipine (NIF) tablets were monitored during the first 3 hours and again after 12, 24 and 48 hours in six hypertensive patients. The maximal hypotensive effect was observed at 3 hours. Following the 40 mg NIF dose, systolic blood pressure (SBP) fell from a mean value (+/- s.e.m.) of 181 +/- 5.7 mmHg to 151 +/- 6.4 mmHg (p less than 0.001) and the diastolic blood pressure (DBP) from a mean of 111 +/- 3.8 mmHg to 91 +/- 3.0 mmHg (p less than 0.001). No significant further reduction was found with the 60 and 80 mg dose. At doses above 40 mg the hypotensive effect lasted up to 24 hours. A linear correlation was found between the dose given and the area under the NIF plasma concentration time curve, as well as with the peak plasma levels for each dose. Mean plasma levels were maximal at 3 hours for each dose. The overall correlation between the NIF plasma concentration and the drop in blood pressure was r = -0.388 for SBP and r = -0.421 for DBP (n = 141). Marked interindividual variation was found for the correlation between plasma levels and the change in blood pressure. Adverse effects were minimal.