Effects of Chlorthalidone on Serum and Total Body Potassium in Hypertensive Patients

Abstract

Total body K was estimated in 26 hypertensive patients who were hypokalemic as a result of long-term chlorthalidone treatment (mean 20.5 mo.), while they were on chlorthalidone and 4 wk after this was discontinued. The mean difference amounted to only 95 meq (not significant). In 6 additional patients not previously treated with chlorthalidone, serial total body K estimations revealed a mean K deficiency of 245 meq after 33 days and of 106 meq after 100 days. The mechanism causing the initial K loss is partly reversed or compensated later on. In patients with uncomplicated hypertension, no significant K deficiency was detected during long-term treatment. Eighteen patients received 39 meq KCl supplements daily for 4 wk; this caused a mean rise in serum K from 3.23 meq/l to 3.38 meq/l (not significant). Total body K did not change. KCl supplements are not an effective treatment of hypokalemia in this condition. Correction of the extracellular pH by NH4Cl in 6 patients on chlorthalidone, who demonstrated a slight metabolic alkalosis, gave rise to a mean increase in plasma K from 2.78 meq/l to 2.96 meq/l (not significant). The hypokalemia in hypertensive patients on long-term chlorthalidone treatment cannot be explained by either a K deficiency or the change in extracellular pH.