Calcium antagonists and sodium balance: effect of changes in sodium intake and of the addition of a thiazide diuretic on the blood pressure lowering effect of nifedipine.

The acute blood pressure lowering effect of nifedipine as a capsule was enhanced by a high-sodium intake in both normotensive and hypertensive subjects. In a double-blind, randomised, placebo-controlled study, the longer-term effect of nifedipine as a tablet in hypertensives was also greater on a high sodium intake than on a normal or low sodium diet. In hypertensive patients who were already on regular treatment with nifedipine, the addition of a thiazide diuretic for 1 month did not cause any significant additional fall in blood pressure despite untoward metabolic side effects. These findings, therefore, strengthen the view that there is a link between the blood pressure lowering activity of calcium entry antagonists and the state of sodium balance.