Role of bile acids
After bariatric surgery, the influence of digestive content is also altered. Gastric acid secretion is significantly reduced following RYGB surgery, leading to an increase in pH in the stomach12,13. The altered GI tract may also lead to a delayed action of bile acids. Because bile salts do not reach the GI tract before the jejunum, contact between bile acids and a drug occurs later in comparison to normal subjects. A drug that has been demonstrated to be dependent on bile acids is fenofibrate. Gesquiere et al. performed a single-dose pharmacokinetic study in 12 RYGB surgery patients before and 6-9 months after surgery and surprisingly, the AUC0–∞, Cmax, and Tmax of fenofibrate were not altered30. The authors hypothesize that these results may be explained by higher fasting total serum bile acid concentration in patients after RYGB and by faster gastric emptying that might compensate for the delayed efflux of bile acids 30. These study results suggest that the overall influence of altered timing of bile acids on oral drug absorption may be minor.