[Effects of a calcium antagonist (nifedipine) in hypertensive and normotensive subjects].

We investigated the effect of the calcium antagonist nifedipine upon the following parameters: systolic and diastolic blood pressure (SBP and DBP) heart rate (HR), electrocardiogram (ECG) and the relative rate of calcium uptake in platelets. The possible correlation between this rate and blood pressure was one of the main points we tried to establish. The subjects studied were 1) 26 patients with uncomplicated essential hypertension and 2) 13 healthy normotensive subjects. SBP and DBP were measured with the subject both in a recumbent and a sitting position. 10 mg of nifedipine were given orally. In the hypertensive patients SBP and DBP decreased significantly in both positions after receiving the drug, as expected, while HR increased significantly (P less than 0.001), also in both positions. In the normotensive subjects BP decreased too, after taking the drug, but was only significantly modified in some instances i.e. SBP recumbent, DBP recumbent and sitting. HR increased significantly in the sitting position but not in the recumbent position. The ECG post-nifedipine showed a negative depression of the ST segment in four patients from the hypertensive group. The relative rate of calcium uptake in platelets measured before the subjects had taken the drug decreased after it was administered. The difference was significant (P less than 0.05) in the hypertensive group, but not in the normotensive group. Some correlation was found between DBP and the rate of calcium uptake.