Duration of effect of different diuretics.

Twenty-four patients with hypertension were treated with chlorothiazide, chlorthalidone, and frusemide. Each diuretic had a significant and similar antihypertensive effect. After cessation of the administration of diuretics, the antihypertensive effect persisted for a longer time with chlorthalidone than with the other two drugs. The full antihypertensive effect of chlorthalidone and chlorothiazide was still present 24 hours after the administration of the drugs was ceased, and the full effect of chlorthalidone was present 72 hours after the administration of the drug was ceased. Side effects related to a rapid diuresis were more common with frusemide. The study indicated that chlorthalidone could be given at 48-hour or 72-hour intervals, and that other diuretics may be given once daily to exert their full antihypertensive action.