Chronic kidney disease incidences in Thai outpatients diagnosed with psychiatric illnesses receiving lithium maintenance therapy: a university hospital-based study.

Background: There has been no previous study in Thailand regarding the incidence of lithium-induced abnormal renal function. Hence, this study aimed to assess the effect of lithium maintenance therapy on chronic kidney disease, and associated factors among outpatients diagnosed with a psychiatric illness within Southern Thailand.

Methods: This was a retrospective study, using an information review from the electronic medical records of Songklanagarind Hospital computer system in the last ten years; from 1 January 2013 until 31 September 2022. Chronic kidney disease was defined as an estimated glomerular filtration rate of less than 60 mL/min/1.73 m and persisted for three months or more. There were 461 outpatients diagnosed with a psychiatric illness who received lithium maintenance therapy. From this, 154 outpatients were excluded: 153 received lithium therapy for less than three months and 1 presented with a baseline chronic kidney disease. All data were analyzed using Rstudio 4.3.1. The incidence of lithium-induced chronic kidney disease was analyzed by survival analysis.

Results: Of the 307 outpatients diagnosed with a psychiatric illness and received lithium maintenance therapy, the most common diagnosis was bipolar disorder (59.3%). Most were female (52.8%), with the median (IQR) age of 39.0 (27.5-54.0) years. The median (IQR) age onset of lithium therapy and duration of lithium maintenance therapy were 28.0 (21.0-41.5) years, and 2.97 (0.9-9.2) years, respectively. This study identified six outpatients (1.9%) that developed chronic kidney disease stage 3 or more and one of them (0.3%) presented with chronic kidney disease stage 5 or end-stage. The incidence of lithium-induced chronic kidney disease was 0.0023 cases per exposed patient-year. When comparing outpatients who had received lithium maintenance therapy and developed chronic kidney disease with those who did not develop chronic kidney disease, this study identified that most of the group with chronic kidney disease had a lithium maintenance therapy for more than ten years, had an older age onset of lithium therapy, reported history of psychiatric hospitalization and lithium intoxication, and presented with physical illness. The associated factors between the effect of lithium maintenance therapy and chronic kidney disease could not be identified due to a limited number of outpatients having developed chronic kidney disease.

Conclusions: Lithium-induced chronic kidney disease was identified as a minor incidence, and it was likely safe for maintenance therapy with careful and regular monitoring. However, older patients or those receiving lithium for a longer time and present with comorbid physical illnesses should be prescribed with caution.

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