Chlorpropamide-induced hyponatremia in the veteran population

OBJECTIVE: To determine the incidence and possible risk factors associated with chlorpropamide (CPA)-induced hyponatremia in the veteran population. DESIGN: Retrospective cohort study. SETTING: Federal tertiary care medical center. PATIENTS: Veterans receiving CPA from our facility with at least one serum sodium concentration below 135 mmol/L within the past year were eligible. A randomly selected control group consisting of patients taking CPA with normal sodium concentrations was also chosen. One hundred forty-five of 799 patients who had received CPA were included in the study. RESULTS: The average daily dose of CPA was 425 +/- 207 mg (+/- SD). The incidence of hyponatremia associated with CPA was 7.1 percent (57/799 patients). The majority of patients were mildly hyponatremic (48/57 patients, 84 percent) with serum sodium concentrations between 130 and 134 mmol/L. The incidence of CPA-induced syndrome of inappropriate antidiuretic hormone was 2.1 percent. Concurrent angiotensin-converting enzyme (ACE) inhibitor use was identified as a risk factor; thiazide diuretic use was not. CONCLUSIONS: The incidence of hyponatremia related to CPA use in elderly veterans is consistent with other reports in the literature. ACE inhibitors may be a predisposing factor for CPA-induced hyponatremia.