Natriuretic effect of barnidipine, a long-acting dihydropyridine calcium channel blocker, in patients with essential hypertension.

Objective: To evaluate the effect of barnidipine hydrochloride, a long-acting dihydropyridine calcium channel blocker on urinary sodium excretion in patients with essential hypertension. Patients: Twelve patients (2 males, 10 females) with mild to moderate essential hypertension. Methods: A single-blinded study. After the control (placebo) period, 10 to 15 mg barnidipine hydrochloride was administered for 7 days, followed by a post-treatment (placebo) period. Daily changes in blood pressure, urinary volume, and urinary electrolyte excretions were evaluated. Plasma levels of atrial natriuretic peptide (ANP) and aldosterone were also determined in each period. Daily sodium intake was kept at 120 mEq. Results: Blood pressure decreased from 161 ± 4/92 ± 2 mmHg to 146 ± 4/85 ± 2 mmHg (p<0.05) after 7-day-treatment with barnidipine. Barnidipine significantly increased urinary sodium excretion; the change was evident on the first day of administration (control period 41 ± 3 mEq/day, and first day 59 ± 3 mEq/day, p < 0.05). Drug discontinuation transiently decreased sodium excretion to 35 ± 3 mEq/day. Cumulative sodium balance after 7-day-treatment reached -47 ± 19 mEq. Urine volume, potassium excretion, and creatinine excretion did not change during the treatment period. The plasma levels of ANP tended to increase, but those of aldosterone did not change with barnidipine. Conclusion: Barnidipine administration for a week decreased the blood pressure and made the sodium balance negative by increasing the urinary sodium excretion in patients with essential hypertension. The natriuretic effect ofthis drug could contribute at least in part to its antihypertensive effect.