Verapamil-induced natriuretic and diuretic effects: dependency on sodium intake

The influence of dietary sodium on the antihypertensive effects of verapamil and on components of sodium, water, and calcium metabolism was studied in nine white patients 50 to 65 years old with normal renin hypertension. Diets consisting of 109 and 259 mEq Na were given for 5 days each before the study drug was given. On days 4 and 9, intravenous verapamil (0.075 mg/kg) and oral verapamil (80 mg) were given, followed by 80 mg at 8-hour intervals for three doses. On days 1, 4, 5, 9, and 10, serum and urine electrolytes, osmolality (urine [Uosm], serum [Sosm], and osmolar clearance [Cosm]), calcium plasma renin activity (PRA), and levels of serum aldosterone, 1,25-hydroxyvitamin D, serum ionized calcium, parathyroid hormone, atrial natriuretic hormone (atriopeptin), and erythrocyte calcium and electrolytes were measured. On days 5 and 10, serial plasma samples for measurement of verapamil and norverapamil levels were drawn immediately after the last oral dose of verapamil. After verapamil, Uosm and Cosm decreased during both 109 and 259 mEq sodium diets (Uosm, p less than 0.025; Cosm, p less than 0.01 and p less than 0.025, respectively), but free water clearance increased during each diet (p less than 0.01). Urine volume and sodium excretion increased with the 259 mEq sodium diet (p less than 0.025 and p less than 0.01, respectively). There were no significant changes in measured values of components of calcium metabolism with either diet or after verapamil.(ABSTRACT TRUNCATED AT 250 WORDS)