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

Abstract

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.