The effect of hydrochlorothiazide and amiloride administered together on muscle electrolytes in normal subjects.

Hydrochlorothiazide, 150 mg daily, and amiloride, 15 mg daily, have been administered together to 10 normal subjects during one week. Muscle biopsies were performed before and after the period of administration of the diuretics and the material was analysed for water and electrolytes. The body weight decreased by 1.9 kg. The serum sodium, chloride and potassium concentrations decreased significantly and standard bicarbonate and blood pH increased. In muscle tissue, extracellular water, chloride and sodium contents and intracellular sodium concentration decreased but the muscle potassium content, the intracellular potassium concentration and the muscle magnesium content were unchanged. A comparison with the results of an earlier study, in which hydrochlorothiazide was given without amiloride, showed that the intracellular potassium depletion and the increase in intracellular sodium concentration, observed with the benzothiazide diuretic, could be fully prevented by simultaneous administration of amiloride. The degree of hypokalemia and alkalosis was also smaller with hydrochlorothiazide + amiloride than with hydrochlorothiazide alone.