In the case of the majority of studied drugs , an increased absorption rate was observed early after RYGBP .
The effect on systemic exposure allows for a low degree of extrapolation , including between drugs subjected to the same major metabolic and transporter pathways .
Anatomical changes in the gastrointestinal tract and subsequent weight loss may influence drug disposition and thus drug dosing following bariatric surgery .
This review systematic ally examines the effects of bariatric surgery on drug pharmacokinetics , focusing especially on the mechanisms involved in restricting oral bioavailability .
Long-term effects of gastric bypass and duodenal switch on systemic exposure of atorvastatin
Background A previous study of 22 patients undergoing either gastric bypass or duodenal switch showed increased systemic exposure of atorvastatin acid  3–8 weeks after surgery in the majority of patients . This study aim ed to investigate the long-term effects on systemic exposure of atorvastatin acid in the same group of patients . Methods An 8-h pharmacokinetic investigation was performed a median of 27 months ( range 21–45 months ) after surgery . Systemic exposure was measured as the area under the plasma concentration versus the time curve from 0 to 8 h postdose ( AUC0–8 ) . Linear mixed models with AUC0–8 as the dependent variable were implemented to assess the effect of time , surgical procedure , and body mass index ( BMI ) as explanatory variables . Results The study enrolled 20 patients . The systemic exposure of atorvastatin acid changed significantly over time ( p = 0.001 ) , albeit there was substantial variation between subjects . The effect of time was attenuated but remained significant after adjustment for surgical procedure and BMI ( p = 0.048 ) . The initial AUC0–8 increase seen in the majority of patients 3–8 weeks after surgery was normalized long term , with 7 of the 12 gastric bypass patients and 6 of the 8 duodenal switch patients showing decreased AUC0–8 compared with preoperative values . Conclusions The systemic exposure of atorvastatin showed a significant change over time after bariatric surgery , albeit with large inter- and intraindividual variations . The findings indicate that patients using  atorvastatin  or drugs with similar pharmacokinetic properties should be monitored closely for both therapeutic effects and adverse events the first years after gastric bypass and duodenal switch . Clinical Trial NCT00331565
In the case of the majority of studied drugs , an increased absorption rate was observed early after RYGBP .
The effect on systemic exposure allows for a low degree of extrapolation , including between drugs subjected to the same major metabolic and transporter pathways .
Anatomical changes in the gastrointestinal tract and subsequent weight loss may influence drug disposition and thus drug dosing following bariatric surgery .
This review systematic ally examines the effects of bariatric surgery on drug pharmacokinetics , focusing especially on the mechanisms involved in restricting oral bioavailability .