Low dose hydrochlorothiazide (12.5 to 25 mg daily) as monotherapy in black patients with mild to moderate hypertension: Assessment by ambulatory blood pressure monitoring

The efficacy of low dose (12.5 to 25 mg daily) hydrochlorothiazide (HCTZ) was evaluated by ambulatory blood pressure monitoring (ABPM) in 19 mild to moderate hypertensive (mean daytime 12-h diastolic BP ≥90 mm Hg and <115 mm Hg) South African black patients. After a 3-week placebo runin period, HCTZ was administered for 8 weeks as monotherapy. The mean daytime ABPM was reduced from 159 ± 13/105 ± 6 to 145 ± 11/97 ± 10 mm Hg (P< .005). Only 6/19 (32%) patients achieved BP control. The 24-h BP load fell from 69% at baseline, to 53% with 12.5 mg HCTZ and to 47% with 25 mg HCTZ daily. There were no side effects but the increase of HCTZ to 25 mg daily was followed by adverse changes (P< .05) in serum potassium levels. It is concluded that low dose HCTZ monotherapy has only a moderate effect on BP control and 24-h BP load while the higher 25 mg dose is associated with significant decrease in serum potassium level.