Acute and sustained changes in sodium balance during nifedipine treatment in essential hypertension.

PURPOSE

To assess the changes in sodium excretion and sodium balance after initiation of nifedipine treatment and after withdrawal of nifedipine.

PATIENTS

Eight patients with uncomplicated mild to moderate essential hypertension were entered in a single-blind, placebo-controlled study of 39 days' duration.

METHODS

Two 7-day periods while on a fixed sodium intake of 150 mmol/day approximately 3 weeks apart. After 4 days of a placebo and fixed sodium intake, patients were given nifedipine GITS (gastrointestinal therapeutic system) once a day and carefully studied for the following 4 days. Thereafter, patients continued to receive nifedipine GITS, and approximately 3 weeks later they were studied again for a week while on a fixed sodium intake. Nifedipine administration was stopped and changes occurring after withdrawal were studied.

RESULTS

Nifedipine caused a significant increase in sodium excretion with a cumulative loss of sodium of 38 mmol per subject within the first 4 days of treatment. The withdrawal of nifedipine treatment caused a significant decrease in sodium excretion and a cumulative retention of sodium of 42 mmol per subject within the first 4 days of withdrawal.

CONCLUSION

Nifedipine causes an acute and a sustained reduction in sodium balance in patients with essential hypertension. This prolonged effect may contribute to the mechanism whereby nifedipine lowers blood pressure.