(1011) Bupropion and Mirtazapine Use in Elderly Patients at Risk of Hyponatremia

Introduction: Hyponatremia is one of the most common electrolyte imbalances in hospitalized geriatric patients. Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) causes chronic hyponatremia and can be induced by first-line antidepressants such as Selective-serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), making them undesirable in high-risk patients. Bupropion and mirtazapine are recommended as safer choices than SSRIs/SNRIs due to sparsity of SIADH reports on them, but there is limited data comparing them in high-risk populations.

Methods: Retrospective chart review of patients admitted at NYU Langone Hospital-Long Island from January 2022 to December 2022. Patients were included if they were aged ≥65 years, received either bupropion, mirtazapine or escitalopram (SSRI control) while admitted, and had at least one additional risk factor for hyponatremia. Patients were excluded if they received concurrent SSRI or SNRI therapy, as well as concurrent study drug (bupropion or mirtazapine). Primary safety outcome was occurrences of hyponatremia (Na+ ≤135 mEq/L) accompanied by a Naranjo score of ≥1 and additional diagnostic lab markers for SIADH. Secondary outcomes included change in Na+ level at day 7 and 30 after drug initiation, occurrence of severe hyponatremia (Na+ ≤125 mEq/L), and non-occurrences of hyponatremia in patients with SIADH history.

Results: There were significantly more hyponatremia occurrences likely induced by the drug in the escitalopram control group (33.8%) compared to bupropion and mirtazapine (8.9%, 8.8%, respectively, p< 0.0001), but there was no difference between bupropion and mirtazapine study groups (p=1.00). There was a statistically significant difference favoring mirtazapine in change in Na+ level at day 30 (p=0.016), however many patients had missing Na+ lab data at this timepoint. There were no statistical differences at the other secondary outcomes.

Conclusions: Bupropion and mirtazapine have statistically less risk of hyponatremia/SIADH in elderly patients at high-risk and can be considered as safe alternatives to SSRIs.