A Comparison of Chlorothiazide, Chlorthalidone and Cyclopenthiazide in the Treatment of Hypertension

A crossover comparison of chlorthalidone and chlorothiazide was conducted to test the relative effectiveness of these two drugs as adjuncts to antihypertensive drugs in the long-term treatment of hypertension. It was found that 100 mg of chlorthalidone daily produced a high incidence of side effects. Fifty milligrams of chlorthalidone daily and 0-5 gm of chlorothiazide twice daily had similar antihypertensive effects, but even this dose of chlorthalidone was still associated with significant hypo- kalaemia. It is suggested that if chlorthalidone is to be used in the long-term treatment of hypertension, the most appropriate dose for most patients is probably 25 mg daily or 50 mg on alternate days.