Carbamazepine Therapy After Bariatric Surgery: Eight Sleeve Gastrectomy Cases and Review of the Literature

Bariatric surgery modifies the anatomy and physiology of the gastrointestinal tract. Carbamazepine (CBZ) is an anticonvulsant with multiple neuropsychiatric indications. Given CBZ physicochemical properties and narrow therapeutic index, bariatric surgery may potentially introduce clinically significant changes in CBZ oral absorption and bioavailability. In this communication, we describe eight patients undergoing sleeve gastrectomy (SG) and treated with CBZ, including therapeutic drug monitoring (TDM) and dosage adjustments at different timeframes before vs. after the surgery (< 3, 4–6, and 7–12 months post-SG), as well as clinical outcomes. We then provide a review of the available literature on CBZ therapy among bariatric patients, concluding with a mechanistic analysis of the results. Four of the eight patients presented with decreased post-SG CBZ levels, and two of them also experienced significant worsening of their previously well-controlled disease. Overall, altered CBZ levels are likely for at least a year after SG. Clinical recommendations include consultation with a clinical pharmacist, careful clinical monitoring, and periodic TDM after (vs. before) the bariatric surgery.