Nifedipine, sodium intake, diuretics, and sodium balance.

The acute blood pressure-lowering effect of nifedipine was studied in patients on high, normal, and low sodium diets. The demonstrated decrease in blood pressure was greatest in those patients receiving the high sodium diet. Studies were then performed with a combination of nifedipine and the diuretic bendrofluazide. When nifedipine was given to patients already on bendrofluazide, there was an additional fall in blood pressure. However, when bendrofluazide was added to the regimen of patients already receiving nifedipine, there was no further reduction in blood pressure. Studies were then performed in patients receiving chronic nifedipine therapy who had their nifedipine treatment stopped while on a fixed sodium intake. All patients retained sodium and there was an increase in weight. This latter study confirms that nifedipine causes a long-term reduction in sodium balance in patients with essential hypertension. It is possible that these long-term changes in sodium balance with nifedipine could partially explain the blunting of the blood pressure-lowering effect seen when the thiazide diuretic was added to the regimen of patients already receiving nifedipine.