Evaluation of Hyponatremia in Patients on Fluoxetine Therapy at a Psychiatry Outpatient Department in a Tertiary Care Hospital: A Cross-sectional Study

Abstract

Introduction: Fluoxetine is a widely used Selective Serotonin Reuptake Inhibitor (SSRI) for various psychiatric illnesses. Identifying patients at increased risk of developing hyponatremia is essential for safe and successful treatment. Aim: To estimate the prevalence of hyponatremia in patients on fluoxetine therapy attending the Psychiatry Outpatient Department (OPD) at a tertiary care hospital and to compare the changes in serum sodium levels between patients younger than 55 years and those older than 55 years on fluoxetine therapy. Materials and Methods: The present cross-sectional study was conducted in the Outpatient Psychiatry Department of Tirunelveli Medical College and Hospital, Tirunelveli, Tamil Nadu, India over three months, from October 2022 to December 2022. It included patients on fluoxetine therapy for various psychiatric illnesses. The type and duration of psychiatric illness, detailed drug history, and any history suggestive of symptoms of hyponatremia were documented. Blood samples were collected for serum sodium level monitoring. Adverse drug reactions to fluoxetine were recorded and assessed for causality, severity, and preventability using the World Health Organisation (WHO)- Uppsala Monitoring Centre causality assessment scale, the modified Hartwig and Siegel scale, and the modified Schumock and Thornton scale, respectively. Descriptive statistics were used to analyse baseline and demographic characteristics. The comparison of sodium levels between patients younger than 55 years and those older than 55 was performed using the MannWhitney U test. Results: The mean age of the study participants being 41.03±13 years. The mean age of the males was 39±15.19 years, and that of the females was 42.05±12.29 years. A total of 30 participants were included in the study. Moderate depression was the most common condition for which fluoxetine was prescribed. Hyponatremia was present in 16.7% of the study participants. The median sodium level was 139±4.5 mEq/L in patients aged less than 55 years and 137±4 mEq/L in patients aged more than 55 years, with a p-value of 0.073. Among the reported adverse reactions, 64.5% were classified as possible, 67.74% as mild, and 58% as probably preventable. Conclusion: Serum electrolyte monitoring is not routinely performed in all patients on fluoxetine. Therefore, relying solely on symptoms to detect hyponatremia may lead to underdiagnosis. Consequently, routine and frequent testing of serum sodium levels is recommended to prevent complications associated with hyponatremia.