A crossover trial of oxdralazine in hypertension.

Twenty-nine moderate and severe essential hypertensive patients completed a crossover study aimed at evaluating efficacy and tolerability of a double combination (chlorthalidone plus propranolol) and of a triple combination (chlorthalidone plus oxdralazine plus propranolol). After one month on 25 mg/day chlorthalidone, which caused nonsignificant reduction in blood pressure of 7/4 mm Hg, patients were randomized to receive either the double or triple regimen for a three-month period. Then, after another month on chlorthalidone alone at the same dose of 25 mg/day, treatments were crossed over and the study continued for another three-month period. The double regimen caused a drop in pressure of 16/11 mm Hg after one month (daily doses 25 mg chlorthalidone, 103 +/- 25 mg propranolol), and this reduction did not change at the third month in spite of dosage increases (daily doses 25 mg chlorthalidone, 222 +/- 77 mg propranolol). The triple regimen reduced blood pressure 35/15 mm Hg after one month (daily doses 25 mg chlorthalidone, 20 mg oxdralazine, 40 mg propranolol), and further increase in dosages caused a reduction of 45/24 mm Hg at the third month (daily doses 25 mg chlorthalidone, 56 +/- 20 mg oxdralazine, 112 +/- 40 mg propranolol). Both treatments were well tolerated; in particular, at the end of the third month of each treatment period, 25 patients on the triple regimen achieved a stable diastolic blood pressure of 90 mm Hg or less, as compared to 10 patients on the double regimen (P less than 0.01).