Nifedipine, diuretics and sodium balance.

There is controversy about the antihypertensive effect of thiazide diuretics in patients already being treated with nifedipine. Studies that we have conducted suggest that the antihypertensive effect of the thiazide may be blunted in the presence of nifedipine. One possible explanation for this blunted response is that nifedipine has a long-term effect on sodium balance. In a study where long-term nifedipine was withdrawn from hypertensive patients there was evidence that withdrawal of nifedipine was accompanied by sodium retention, as judged by changes in urinary sodium excretion. If these results are confirmed in larger studies, they have important therapeutic implications for the use of nifedipine.