Potassium loss associated with hydrochlorothiazide versus chlorthalidone

A retrospective survey using chart review was conducted to determine the incidence of clinically significant hypokalemia resulting from therapy with chlorthalidone (CTLD) or hydrochlorothiazide (HCTZ). The frequency of hypokalemia, potassium less than or equal to 3.0 mEq/liter, was 4/29 patients (13.8%) in the CTLD once-daily group, 0/17 in the HCDL twice-daily group, and 0/31 in the HCTZ once-daily group. Using the Fisher exact probability test, a significant difference in the incidence of hypokalemia was observed between the CTLD once-daily and HCTZ once-daily groups. From the results, it is apparent that a diuretic's duration of actions, as represented by HCTZ (short-acting) and CTLD (long-acting), influences serum potassium concentrations; CTLD produced a greater incidence and degree of hypokalemia.