Effect of bariatric surgery on the pharmacokinetics of drugs used for attention-deficit hyperactivity disorder-A case series.

Background: Changes in gastrointestinal physiology following bariatric surgery may affect the pharmacokinetics of drugs. Data on the impact of bariatric surgery on drugs used for attention-deficit/hyperactivity disorder (ADHD) are limited.

Methods: In patients treated with ADHD medication and undergoing bariatric surgery, serial drug concentrations were measured for 24 h preoperatively and one, six and 12 months postoperatively. Primary outcome was change in area under the concentration-time curve from 0 to 24 h (AUC_0-24), with other pharmacokinetic variables as secondary outcomes.

Results: Eight patients treated with lisdexamphetamine (n = 4), dexamphetamine (n = 1), methylphenidate (n = 1) and atomoxetine (n = 2) were included. In total, 409 samples were analysed. Patients underwent sleeve gastrectomy (n = 5) and Roux-en-Y gastric bypass (n = 3). AUC_0-24 and C_max of dexamphetamine increased after surgery in those using the prodrug lisdexamphetamine. There was no clear-cut reduction in t_max postoperatively. For ritalinic acid and atomoxetine, no changes in AUC_0-24 were observed, but for atomoxetine, a higher C_max and a shorter t_max were observed postoperatively.

Conclusion: Bariatric surgery may increase the systemic exposure of dexamphetamine after intake of lisdexamphetamine. Patients using lisdexamphetamine should be followed with regard to adverse drug reactions after bariatric surgery, and, if available, therapeutic drug monitoring should be considered.