Fixed-Dose Combinations Containing Thiazide as the Common Cause of Severe In-Hospital Hyponatremia

Abstract

BACKGROUND: Since thiazides are recommended as the first-line agent for the treatment of hypertension, the prescription of rued-dose combinations (FDC) containing thiazides has increased. We aimed to evaluate the clinical presentations of FDC-related severe hyponatremia.METHODS: In a study period of 30 months, 149 patients with a serum sodium concentration ≤125 mEq/L upon admission were retrospectively reviewed. Patients were followed up for 6 months after being discharged.RESULTS: FDC was a common cause of severe hyponatremia, accounting for 30% of the cases studied (n = 44); while thiazides alone accounted for 11.4% only (n = 17). After FDC prescription, only 9.1 % (n = 4) of the patients underwent serum sodium measurement. Of the 44 patients having FDC-related hyponatremia, 36.4% (n = 16) and 70.4% (n = 31) encountered severe hyponatremia during the first month and within three months, respectively. Patients with FDC-related hyponatremia had lower morbidity than those with non-FDC related hyponatremia (P = 0.041); and patients with FDC- or thiazide-related hyponatremia had lower mortality during hospitalization than those with non-thiazide-related hyponatremia (P = 0.076). The 6-month recurrence rate of severe hyponatremia did not differ between patients with FDC-related severe hyponatremia and those with non-FDC-related severe hyponatremia (16.3% vs. 23.5% vs. 33.3%, P = 0.268).CONCLUSION: TFDC has emerged as the usual cause of severe hyponatremia in this assessed population. Once severe hyponatremia is encountered, prompt discontinuation of the offending FDC with or without isotonic saline infusion might be the best management strategy and the prognosis appears to be good. A larger number of patients and medical centers are necessary to further validate this conclusion.