Antihypertensive effects of low doses of hydrochlorothiazide in hypertensive black Zimbabweans.

The antihypertensive effects of low doses of hydrochlorothiazide have not been examined in black African hypertensive patients although hydrochlorothiazide is commonly used as first-line therapy. The antihypertensive effects of hydrochlorothiazide in a daily dose of 6.25, 12.5, 25 and 50 mg were examined in 19 black Zimbabwean hypertensive patients in a double-blind, random order, placebo-controlled, cross-over trial. The mean systolic blood pressure on placebo was 170.2 mmHg (95% CI +/- 9.0 mmHg) and on daily doses of hydrochlorothiazide decreased to: 161.1 mmHg (95% CI + 10.0 mmHg) on 6.25 mg; 156.6 mmHg (95% CI +/- 8.6 mmHg) on 12.5 mg; 154.9 mmHg (95% CI +/- 8.5 mmHg) on 25 mg and 149.1 mmHg (95% CI +/- 9.2 mmHg) on 50 mg. The mean diastolic blood pressure on placebo was 101.4 mmHg (95% CI +/- 5.0 mmHg) and decreased to: 98.0 mmHg (95% CI +/- 5.7 mmHg) on 6.25 mg; 96.1 mmHg (95% CI +/- 4.5 mmHg) on 12.5 mg; 93.6 mmHg (95% CI +/- 5.3 mmHg) on 25 mg and 90.5 mmHg (95% CI +/- 3.9 mmHg) on 50 mg. Hydrochlorothiazide in doses of 25 mg and 50 mg decreased systolic and diastolic blood pressure and the 12.5 mg dose decreased systolic blood pressure significantly more than placebo. We conclude that in this population maximum antihypertensive effect is not seen with the lower doses of hydrochlorothiazide and 25 mg is an appropriate starting dose for most patients.