INFLUENCE OF RACE AND DIETARY SALT ON THE ANTIHYPERTENSIVE EFFICACY OF AN ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR OR A CALCIUM-CHANNEL ANTAGONIST IN SALT-SENSITIVE HYPERTENSIVES

Dietary salt restriction is a recommended adjunct with antihypertensiv e therapy. There may be racial differences in blood pressure response to salt restriction while on antihypertensive therapy. We performed a multicenter, randomized, double-blind, placebo-controlled, parallel-gr oup clinical trial (black, n=96; Hispanic, n=63; white, n=232). Partic ipants were initially preselected for stage I to III hypertension and then further selected for salt sensitivity (greater than or equal to 5 mm Hg increase in diastolic blood pressure after 3 weeks of low salt [less than or equal to 88 mmol/d Na+] and high salt [>190 mmol/d Na+] diet). We compared the antihypertensive effect of an angiotensin-conve rting enzyme inhibitor (enalapril 5 or 20 mg BID) or a calcium channel antagonist (isradipine 5 or 10 mg BID) during alternating periods of high and low salt intake. The main outcome measure was blood pressure change and absolute blood pressure level achieved with therapy. During the high salt diet (314.7+/-107.5 mmol/d urinary Na+) there was great er downward change in blood pressure with both enalapril and isradipin e compared with the low salt diet (90.1+/-50.8 mmol/d Na+); however, t he absolute blood pressure achieved in all races was consistently lowe r on a low salt diet for both agents. Black, white, and Hispanic israd ipine-treated salt-sensitive hypertensives demonstrated a smaller diff erence between high and low salt diets (black, -3.6/-1.6 mm Hg; white, -6.2/-3.9 mm Hg; Hispanic, -8.1/-5.3 mm Hg) than did enalapril-treate d patients (black, -9.0/-5.3 mm Hg; white, -11.8/-7.0 mm Hg; Hispanic, -11.1/-5.6 Mn Hg). On the low salt diet, blacks, whites, and Hispanic s had similar blood pressure control with enalapril and isradipine. On the high salt diet, blacks had better blood pressure control with isr adipine than with enalapril, whereas there was no difference in the bl ood pressure control in whites and Hispanics treated with either drug, Dietary salt reduction helps reduce blood pressure in salt-sensitive hypertensive blacks, whites, and Hispanics treated with enalapril or i sradipine. These data demonstrate that controlling for salt sensitivit y diminishes race-related differences in antihypertensive activity.