The Influence of a Roux-en-Y Gastric Bypass on Plasma Concentrations of Antidepressants

Purpose Roux-en-Y gastric bypass (RYGB) involves alterations of the gastrointestinal tract resulting in altered absorption. Patients with obesity have a higher prevalence of depression, and antidepressants are often prescribed. Alterations caused by RYGB could modify drug bioavailability and cause potential subtherapeutic plasma concentrations, increasing the risk of depressive relapse. The aim of this study was to describe the evolution of trough drug dose-normalized antidepressant plasma concentrations before and after RYGB. Materials and Methods This naturalistic prospective case series considers patients with trough plasma concentrations in a 1-year timeframe before and after RYGB. Only antidepressants prescribed to at least three patients were included in the present study. Results Thirteen patients ( n = 12 females, median age 44 years, median BMI before intervention = 41.3 kg/m 2 ) were included. Two patients were treated concurrently with fluoxetine and trazodone; the remaining patients were all treated with antidepressant monotherapy. Therapeutic drug monitoring (TDM) values for duloxetine ( n = 3), escitalopram ( n = 4), fluoxetine ( n = 4), and trazodone ( n = 4) before (median 4.7 weeks) and after (median 21.3 weeks) RYGB intervention were analyzed. Compared to preintervention, median [interquartile range] decreases in dose-normalized trough plasma concentrations for duloxetine (33% [− 47; − 23]), escitalopram (43% [− 51; − 31]), fluoxetine (9% [− 20; 0.2]), and trazodone (16% [− 29; 0.3]) were observed. Conclusion This study shows a decrease in plasma antidepressant concentrations following RYGB. TDM before and after RYGB, in addition to close monitoring of psychiatric symptomatology, may help optimize antidepressant treatment after bariatric surgery. These results also highlight the need for prospective studies assessing the clinical evidence available through TDM in these patients. Graphical Abstract