Comparison of the antihypertensive efficacy and adverse reactions to two doses of bendrofluazide and hydrochlorothiazide and the effect of potassium supplementation on the hypotensive action of bendrofluazide: substudies of the Medical Research Council's trials of treatment of mild hypertension: Medical Research Council Working Party.

As substudies of the Medical Research Council's trials of treatment of mild hypertension and of hypertension in the elderly, two studies were carried out comparing the effects of different doses of two diuretics on blood pressure, concentrations of some biochemical variables, and the incidence of subjective adverse reactions. In one study, in which 484 patients with mild hypertension participated, daily doses of bendrofluazide 5 mg and 10 mg, with and without oral potassium supplements, were compared. In the second, involving 701 elderly patients with hypertension, daily doses of hydrochlorothiazide 25 mg together with amiloride 2.5 mg were compared with hydrochlorothiazide 50 mg together with amiloride 5 mg. The mean (+/- SD) durations of treatment were 35 +/- 17 months in the first study and 10 +/- 7 months in the second. Neither study showed any significant difference in blood pressure response to the two doses of diuretic, whereas biochemical changes and the reported incidence of subjective adverse reactions were dose-related. In the first study, potassium supplementation with potassium chloride 16.8 or 33.6 mmol did not have a significant effect on the fall in serum potassium level, which was only slightly reduced, and did not have any significant effect on the antihypertensive effect of either dose of bendrofluazide.