Immunosuppressant Dosing and Trough Levels in Transplant Patients That Have Duodenal Bypass Bariatric Surgery.

BACKGROUND: Obesity is associated with increased complications after solid organ transplantation (SOT). While metabolic and bariatric surgery (MBS) improves survival, metabolic, and graft outcomes in transplant patients, we aim to clarify the risk that duodenal bypass MBS (DB-MBS) has on immunosuppression and acute rejection. METHODS: A single-center retrospective cohort study was conducted on patients who underwent SOT and DB-MBS between 2003 and 2025. Immunosuppressant regimens and biopsy-confirmed acute rejection details were collected for 3 years after each procedure. Immunosuppressant dosing and trough levels were normalized to individual target levels and evaluated with linear-mixed effects models. RESULTS: The cohort included 19 patients. There were no statistically significant differences in immunosuppression outcomes when DB-MBS is performed before (dosing P=0.821, trough P=0.916) and after (dosing P=0.368, trough P=0.317) SOT. The 3-year acute rejection incidence was 21.1%. CONCLUSION: The presence and timing of DB-MBS did not significantly alter immunosuppression dosing and trough levels.