Abstract P174: Incidence of Hyponatremia on Spironolactone in Patients With a Prior Episode of Chlorthalidone-Induce Hyponatremia

Chlorthalidone and spironolactone are commonly used diuretics for patients with difficult-to-manage hypertension. Hyponatremia is a common adverse effect that results in discontinuing these medications in many subjects. We designed this study to determine the incidence of hyponatremia on spironolactone after developing a hyponatremic episode on chlorthalidone. Electronic health records were searched for patients seen at UAB’s outpatient clinics. Inclusion criteria included: patients who developed hyponatremia (serum sodium <133 mEq/L) on chlorthalidone within 90 days of starting the medication and had a prescription for spironolactone at another time point. The sodium levels were checked for 90 days after starting spironolactone. Exclusion criteria constituted having one of the following: heart failure, liver cirrhosis or adrenal insufficiency based on ICD 10 codes or an estimated glomerular filtration rate (eGFR) of < 30 mL/min/1.73 m2. Preliminary analysis yielded eligible 14 patients. Eight had hyponatremia on chlorthalidone, but tolerated spironolactone well, and 6 had hyponatremia on both diuretics. Females comprised 13 out of 14 (92.9%) of the population. There were no significant differences in age, gender, race, baseline sodium level, sodium level at the hyponatremic episode or eGFR between the two groups. These findings suggest that checking sodium levels frequently for those who had hyponatremia with chlorthalidone and are prescribed subsequently spironolactone is warranted.