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 .
Orally Administered Ranitidine Plasma Concentrations before and after Biliopancreatic Diversion in Morbidly Obese Patients
Background : Patients undergoing biliopancreatic diversion ( BPD )  may develop gastric ulcers , particularly within the first postoperative year . The prophylactic use of antisecretory compounds at the usual therapeutic doses , mainly conventional H2-receptor antagonists such as ranitidine , may reduce the incidence of this complication , which occurs in ∼5 % of patients after BPD . Methods : The authors measured the plasma concentrations of ranitidine ( 300 mg orally ) in obese patients , before and 8 months after BPD , and in control subjects of normal weight . The study included 11 obese patients undergoing BPD ( age 45 ± 14 years ; preoperative and postoperative weights 124 ± 21 and 92 ± 11 kg ) and 10 normal-weight subjects ( age 37 ± 13 years , weight 67 ± 9 kg ) .  Results : Postoperative ranitidine plasma concentrations showed only minor differences from preoperative levels , with slightly higher maximum concentrations occurring sooner . The mean area under the curve was on the average 30 % higher than preoperatively . All parameters , however , were similar to those in control subjects . Conclusions : BPD per se does not greatly affect the pharmacokinetic behavior of ranitidine , and therefore a conventional dosage regimen appears adequate for the prophylaxis and therapy of gastric ulcers associated with this operation
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 .