Clinical severity of drug-induced hyponatremia: thiazides vs. psychotropics.

Background: The aim of this study was to investigate the clinical characteristics of patients with hyponatremia who received thiazide diuretics, psychotropic drugs, or both. Methods: From 2007 to 2013, 266 patients were diagnosed with hyponatremia (P-Na < 135 mol/L) associated with thiazide diuretics (T), psychotropic drugs (P), or both (C). We compared clinical characteristics among the thiazide (T) group (n = 93), the psychotropic drug (P) group (n = 83), and the combination (C) group (n = 90). Results: There were no differences in clinical characteristics except for correction time among the three groups. We evaluated the clinical severity among the three groups through initial serum sodium levels (mild: > 125 mmol/L, moderate: 120 - 125 mmol/L, severe: < 120 mmol/L), patient symptoms (mild: general weakness, moderate: nausea or vomiting, severe: syncope or seizure). There were no significant differences in the incidence of severe hyponatremia on the basis of initial serum sodium levels (73.1% vs. 67.5% vs. 71.1%, p = 0.710) and symptoms (20.4% vs. 30.1% vs. 17.8%, p = 0.192) among groups. However, correction time was significantly longer in group C than in groups T or P (41.98 +/- 26.89 vs. 34.91 +/- 23.96 vs. 51.10 +/- 43.86 mg/dL, p = 0.026). Conclusion: Although patients in group C did not have clinical features that were any more severe than those of the other two groups in terms of initial serum sodium levels and symptoms, correction time was significantly longer for group C than for groups T or P. Therefore, it is of utmost importance to closely monitor patients who receive a thiazide and psychotropic drug simultaneously.