Changes in Antidepressant Absorption After Metabolic Bariatric Surgery

Metabolic bariatric surgery (MBS), particularly Roux-en-Y gastric bypass (RYGB), is one of the most effective long-term intervention for weight loss, but its hypoabsortive nature may affect drug metabolism.

A retrospective longitudinal study with intra-individual comparisons was conducted on patients who underwent RYGB at Clínica Universidad de Navarra between 2014 and 2019 at our institution and were on antidepressant treatment before and after surgery. Apparent oral clearance (CL/F), concentration/dose ratio (CDR), and weight loss parameters were compared pre- and post-surgery. Measurements were taken at the time of surgery (M1), 1 month after surgery (M2), and between 6 and 15 months after surgery (M3).

Fourteen patients (10 females) with a mean age of 48.92 years and a mean baseline BMI of 37.32 kg/m² were included in the study. They were being treated with fluoxetine (n = 6), duloxetine (n = 2), bupropion (n = 2), sertraline (n = 1), clobazam (n = 1), topiramate (n = 1), and aripiprazole (n = 1). Patients who were within the therapeutic range for their medications prior to surgery remained within that range postoperatively. The fluoxetine + D-fluoxetine concentrations and CDR significantly varied between M1 and M2, with a p-value of 0.022, and an inverse association between BMI and D-fluoxetine CDR was observed (p = 0.004).

These findings suggest, in a small cohort, that chronic use of antidepressants does not require major changes in the management of patients undergoing MBS. Two distinct absorption patterns were identified for different antidepressants after surgery, highlighting the potential influence of metabolic pathways and enzymatic activity. The inverse association between D-fluoxetine CDR and BMI may be linked to changes in CYP enzyme function following MBS.