Hypokalemia during the treatment of arterial hypertension with diuretics.

In a study of 50 patients with uncomplicated arterial hypertension the administration of hydrochlorothiazide, 50 to 100 mg daily or every other day, with or without reserpine, 0.25 mg daily, resulted in a fall in the mean blood pressure from 182/113 to 144/92 mm Hg. The mean duration of therapy was 19 months. The mean serum potassium concentration was 4.3 mmol/l before the onset of therapy. It fell during the first 6 weeks of treatment, but seldom below 3.5 mmol/l, then rose gradually and spontaneously to 4.1 mmol/l after 19 months of therapy. All the patients remained asymptomatic. These findings bring into question the routine use of potassium supplements or a potassium-sparing diuretic, such as spironolactone or triamterene, during the treatment of hypertension with diuretics such as the thiazides. The use of potassium supplements or a potassium-sparing agent may induce hyperkalemia in spite of the simultaneous administration of a diuretic that acts more proximally. Since hyperkalemia is potentially lethal, the serum potassium concentration should be carefully monitored in any patient receiving potassium supplements or a potassium-sparing agent.