A double-blind multicentre study of piretanide and hydrochlorothiazide in patients with essential hypertension.

In a randomized double-blind parallel group study conducted in three centres the hypotensive activity of piretanide 6 mg b.i.d. was compared with that of hydrochlorothiazide (HCT) 25 mg b.i.d. and HCT 50 mg b.i.d. Ninety-three patients entered the study and sixty-one completed a 16-week trial period. All three treatments produced a significant reduction in supine diastolic and systolic blood pressure after only 2 weeks of active treatment and this was maintained for the duration of the study. The mean maximal reduction in supine diastolic blood pressure was 18% in the piretanide group, 18.8% in the HCT 25 mg b.i.d. group, and 20% in the HCT 50 mg b.i.d. group. The corresponding figures for the percentage of patients attaining a supine diastolic pressure below 95 mm Hg were 83%, 62% and 89%. There were no significant differences between the three groups. Side-effects were generally mild and transient, except for polyuria which was noted in all three groups but more commonly in the piretanide group. Two patients were withdrawn because of side-effects: one patient in the high dose HCT group developed severe postural symptoms; and one patient in the low dose HCT group was withdrawn because of restlessness, nausea, weakness, dizziness and somnolence. All three treatments caused a significant increase in serum uric acid concentrations. Four patients in each of the HCT groups developed hypokalaemia, but no patients in the piretanide group did so.