title: Trends in oral drug bioavailability following bariatric surgery: examining the variable extent of impact on exposure of different drug classes.
abstract: BACKGROUND
  Changes to oral drug bioavailability have been observed post bariatric surgery. However, the magnitude and the direction of changes have not been assessed systematically to provide insights into the parameters governing the observed trends. Understanding these can help with dose adjustments.
  
  
  CONCLUSIONS
  Analysis of drug characteristics based on a biopharmaceutical classification system is not adequate to explain observed trends in altered oral drug bioavailability following bariatric surgery, although the findings suggest solubility to play an important role.
  
  
  OBJECTIVE
  To identify the most commonly prescribed drugs in a bariatric surgery population and to assess existing evidence regarding trends in oral drug bioavailability post bariatric surgery.
  
  
  METHODS
  A retrospective audit was undertaken to document commonly prescribed drugs amongst patients undergoing bariatric surgery in an NHS hospital in the UK and to assess practice for drug administration following bariatric surgery. The available literature was examined for trends relating to drug permeability and solubility with regards to the Biopharmaceutics Classification System (BCS) and main route of elimination.
  
  
  RESULTS
  No significant difference in the 'post/pre surgery oral drug exposure ratio' (ppR) was apparent between BCS class I to IV drugs, with regards to dose number (Do) or main route of elimination. Drugs classified as 'solubility limited' displayed an overall reduction as compared with 'freely soluble' compounds, as well as an unaltered and increased ppR.
  
  
  CONCLUSIONS
  Clinical studies establishing guidelines for commonly prescribed drugs, and the monitoring of drugs exhibiting a narrow therapeutic window or without a readily assessed clinical endpoint, are warranted. Using mechanistically based pharmacokinetic modelling for simulating the multivariate nature of changes in drug exposure may serve as a useful tool in the further understanding of postoperative trends in oral drug exposure and in developing practical clinical guidance.
authors.affiliation: Centre of Applied Pharmacokinetic Research, School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Manchester, UK.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Darwich
authors.forename: Kathryn
authors.initials: K
authors.lastname: Henderson
authors.forename: Angela
authors.initials: A
authors.lastname: Burgin
authors.forename: Nicola
authors.initials: N
authors.lastname: Ward
authors.forename: Janet
authors.initials: J
authors.lastname: Whittam
authors.forename: Basil J
authors.initials: BJ
authors.lastname: Ammori
authors.forename: Darren M
authors.initials: DM
authors.lastname: Ashcroft
authors.forename: Amin
authors.initials: A
authors.lastname: Rostami-Hodjegan
mesh_terms: D000284:Administration, Oral; D000328:Adult; D050110:Bariatric Surgery; D001682:Biological Availability; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010539:Permeability; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D017410:Practice Guidelines as Topic; D012189:Retrospective Studies; D012995:Solubility; D055815:Young Adult
chemical_list: D004364:Pharmaceutical Preparations