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.