Kidney function and prescribed dose in middle-aged and older patients starting selective serotonin reuptake inhibitors.

Purpose: To avoid adverse drug reactions, dose reductions are recommended when prescribing selective serotonin reuptake inhibitors (SSRIs) to patients with impaired kidney function. The extent of this practice in routine clinical care is however unknown. We aimed to evaluate the starting and maintenance SSRI doses prescribed to patients stratified by levels of kidney function in real-world practice.

Methods: Using data from the Stockholm CREAtinine Measurements (SCREAM) project, we identified 101 409 new users of antidepressants (including 52 286 SSRI users) in the region of Stockholm during 2006-2019, who were ≥50 years of age and had a recent creatinine test taken in order to estimate glomerular filtration rate (eGFR). SSRI dose reduction was defined as a prescribed SSRI dose of ≤0.5 defined daily doses, according to current recommendations. We examined the associations between eGFR and reductions in initial dose and maintenance dose of SSRIs using logistic regression models.

Results: Overall, reductions in initial and maintenance dose were observed among 54.1% and 34.1% of new SSRI users. Nevertheless, about 40% of individuals with an eGFR <30 ml/min/1.73 m were prescribed an SSRI without dose reduction. After adjusting for age and other covariates, lower eGFR was associated with moderately higher odds of dose reduction, for both initial and maintenance dose. Compared to individuals with an eGFR of 90-104 ml/min/1.73 m , the adjusted odds ratios for those with an eGFR <30 ml/min/1.73 m were 1.18 (95% CI: 1.03, 1.36) for initial dose reduction, and 1.49 (1.29, 1.72) for maintenance dose reduction. Stratified analyses showed stronger associations between lower eGFR and SSRI dose reduction among individuals aged 50-64 years and in those receiving prescriptions from psychiatric care.

Conclusions: Lower kidney function was moderately associated with a reduced SSRI dose, independently of age. Prescribing SSRIs to middle-aged and older patients should not only consider patients' age but also their kidney function.