Dissolution of common psychiatric medications in a Roux-en-Y gastric bypass model

Large numbers of Roux-en-Y gastric bypass (RYGB) surgery patients have psychiatric illnesses that are in part treated with medication preoperatively, but there are no objective data to guide psychiatric drug dosing postoperatively. An in vitro drug dissolution model was developed to approximate the gastrointestinal environment of the preoperative (control) and post-RYGB states. Medication tablets were placed in the two environments, and the median calculated weights of the dissolved portions were compared. Ten of 22 psychiatric medication preparations had significantly less dissolution and two had significantly greater dissolution in the post-RYGB environment, compared with the control environment. The results suggest a need for an in vivo study of serum drug levels after RYGB surgery in patients taking psychiatric medications. Differences in the pharmacokinetics of the postoperative RYGB patient may necessitate adjustments in dosing.