Effect of calcium-entry blockers on the diuretic response to hydrochlorothiazide in the rat.

The influence of the calcium-entry blockers, verapamil, nifedipine and diltiazem on hydrochlorothiazide-induced diuresis was determined in hydrated conscious rats. Nifedipine significantly inhibited hydrochlorothiazide-induced 5-h excreted urine volume and urinary sodium with little effect on potassium excretion. Both verapamil and diltiazem significantly enhanced urinary sodium excretion with no effect on either urine volume or potassium excretion. These results are of interest in view of the current use of nifedipine as an anti-hypertensive agent, alone or in combination with a thiazide diuretic.