Duration of antihypertensive effect of a single daily dose of hydrochlorothiazide

To assess the duration of antihypertensive effect of a single daily dose of the short-acting diuretic hydrochlorothiazide, a double-blind crossover study was performed in 11 patients previously well controlled with diuretics. Each patient received hydrochlorothiazide 100 mg in the morning for 12 wk and blood pressure were recorded 4 times daily (8 A.M., 12 noon, 4 A.M., and 8 P.M) on 3 separate visits. The crossover design also included a 12-wk placebo period either preceding or following active therapy. Blood pressure control was excellent and sustained throughout the day in all patients studied, indicating that a single daily dose of hydrochlorothiazide is a suitable regimen for hypertension therapy. The use of a placebo period before initiating the trial and during the active part of the trial confirmed the observation that patients who have been adequately treated for long periods will maintain lowered blood pressure for a variable period after stopping therapy.