USE OF HOME‐BLOOD‐PRESSURE MEASUREMENT TO COMPARE THE EFFICACY OF TWO DIURETICS: EFFECTS OF METHYCLOTHIAZIDE AND FRUSEMIDE ON BLOOD PRESSURE AND PLASMA RENIN ACTIVITY AND ELECTROLYTES1

Ten ambulant hypertensive patients, whose blood pressure was well controlled and stable on a regime which included a diuretic, were taught to record their blood pressure measurements at home three times daily, in addition to those recorded by the physician each two weeks. The effects of a thiazide diuretic—methyclothiazlde (Abbott), 5 mg—were compared with the effects of frusemide (Hoechst), 40 mg, in a double‐blind, cross‐over trial lasting three months. Methyclothiazide produced better around‐the‐clock control of blood pressure, owing to significantly greater effect in the morning before the next dose was to be taken. Evidence for persistent negative sodium balance in long‐term diuretic therapy was afforded by elevated plasma renin activity levels in six of the ten patients. Methyclothiazide appeared to be more potent as a stimulator of plasma renin activity (not significant), and as a depressor of plasma potassium level (significant). The action of methyclothiazide in slightly lowering serum sodium and chloride levels differed significantly from that of frusemide, which did not. Body weight was lowered significantly more by the end of the trial in patients who received methyclothiazide twice than in those who received frusemide twice. All these differences can probably be explained by the sustained action of methyclothiazide compared with the brief action of frusemide. It is concluded that, provided that potassium depletion is avoided or corrected, the cheaper thiazide diuretic methyclothiazide is preferable to frusemide in the treatment of ambulant hypertensive patients.