OBJECTIVES: Hyponatremia is a common electrolyte disorder among the elderly that can cause serious adverse effects. The purpose of this study was to assess the risk of hyponatremia and the concurrent use of selective serotonin reuptake inhibitors (SSRIs) and thiazide diuretics in a geriatric population.

METHODS: Two retrospective nested case-control studies were conducted with exposure to an SSRI or a thiazide diuretic. Patients of interest include individuals receiving Medicare A, B, and D benefits from 2017 to 2019. Cases were individuals with a diagnosis of hyponatremia. Controls were patients taking either an SSRI or a thiazide diuretic. A logistic regression was conducted to determine the odds of hyponatremia. Data analysis was conducted using SAS.

RESULTS: A total of 551,298 patients with a mean age of 77.8 years (SD:± 8.0 years) were taking an SSRI, 70.5% of which were female and 90.7% were caucasian. A total of 701,007 were taking a thiazide diuretics with a mean age of 77.1 years (SD:± 7.2 years), 63.3% being female and 85.7% being caucasian. Among those on SSRIs, 76,037 had a diagnosis of hyponatremia, while among thiazide users 76,662 had a diagnosis of hyponatremia. Among SSRI users, the odds of hyponatremia with concomitant use of thiazide diuretics was 1.32 (95% CI: 1.30-1.34). For thiazide users, the odds of hyponatremia was 1.52 (95% CI:1.5-1.55) with concomitant use of SSRIs.

CONCLUSIONS: The concurrent use of HCTZ and SSRIs is associated with a significantly increased risk of hyponatremia in the geriatric population.