Pharmacokinetic Changes Secondary to Roux en Y Gastric Bypass

Abstract

Objective: To review the influence of Roux-en-Y gastric bypass (RYGB) on pharmacokinetic parameters of medications.Data sources: PubMed was searched from inception to September 2012 to identify studies. Search terms included bariatric surgery, gastric bypass, Roux-en-Y, pharmacokinetic, and absorption. Studies included for this review were limited to English language studies published in full.Data synthesis: Obesity is a major health care concern and is on the rise. This has led to an increasing number of bariatric surgeries. Such procedures may have profound effects on pharmacokinetic parameters of many medications depending on the extent of surgical changes that are made. Surgical procedures such as RYGB are most likely to affect medication absorption. Factors that may affect medication absorption in RYGB patients include changes in intestinal or gastric pH, surface area, intestinal metabolism and transport mechanisms. Published studies have been primarily conducted in RYGB patients and have shown varied effect on overall absorption of medications.Conclusions: RYGB may have profound effects on medication absorption. Predicting absorption is difficult due to interplay of several factors including, changes in intestinal surface area, intestinal metabolism, efflux pumps, active transporters and gastrointestinal pH. Future studies are needed, particularly studies evaluating medications that have a low bioavailability and are commonly used in the bariatric surgery population.

The Impact of Proximal Roux‐en‐Y Gastric Bypass Surgery on Acetaminophen Absorption and Metabolism

“…In contrast, doses of metformin and atorvastatin need to be decreased due to higher bioavailability and lower clearance post‐surgery . The effect of RYGBS on pharmacokinetics may be drug‐specific depending on the physiochemical properties, metabolic pathways and transport of the drug . Based on a simulation of a multiple dosing regimen (Figure ), post‐RYGBS patients were predicted to have higher steady‐state peak APAP concentrations though APAP exposure was comparable to healthy volunteers.…”

“…43,44 The effect of RYGBS on pharmacokinetics may be drug-specific depending on the physiochemical properties, metabolic pathways and transport of the drug. 45 Based on a simulation of a multiple dosing regimen (Figure 6), post-RYGBS patients were predicted to have higher steady-state peak APAP concentrations though APAP exposure was comparable to healthy volunteers. Post-RYGBS, the higher steady-state peak APAP concentrations may result in depletion of glutathione stores and shunt the metabolism toward the toxic metabolite (NAPQI).…”

Antiseizure Medication use in Gastric Bypass Patients and Other Post-Surgical Malabsorptive States

“…The intraluminal pH of the stomach is normally acidic with a pH of 1.5 to 3.5 while the pH of the small intestine is 6.6 to 7.5 and increases rapidly beyond proximal duodenum to peak at 7.5 in the distal ileum [14] , [15] . After partial or total gastrectomy, as with some bariatric surgeries, the available parietal cells that secrete hydrochloric acid may be reduced or bypassed leading to an increase in gastric pH [13] .…”