title: Bioavailability of Methadone After Sleeve Gastrectomy: A Planned Case Observation.
abstract: Morbidly obese patients on opioid-replacement therapy may be at risk for treatment refusal with regard to bariatric surgery. However, patients on opioid replacement may have the personal skills to facilitate the lifestyle changes required for successful outcomes after bariatric surgery. This planned case observation assessed the effects of sleeve gastrectomy on the pharmacokinetic properties of methadone.
  
  
  
  A white woman in her 40s on methadone maintenance therapy and with morbid obesity was referred for bariatric surgery. Serial blood samples for methadone concentration measurements were obtained before and at 5 days and 1, 7, and 11 months after surgery.
  
  
  
  Serum methadone concentrations increased from before to 5 days after surgery and continued to increase for 7 months thereafter. The predose measurement at 11 months postoperatively suggests a further increase compared with the previous predose measurements.
  
  
  
  Clinicians should beware the potential for altered effects of methadone after bariatric surgery. We recommend that serum concentrations be routinely measured pre- and postoperatively, and that the dose be adjusted according to these measurements and regular clinical assessments.
authors.affiliation: Centre for Obesity Research, Clinic of Surgery, St. Olav University Hospital, Trondheim, Norway; Department of Neuroscience, NTNU, Norwegian University of Science and Technology, Trondheim, Norway. Electronic address: magnus.strommen@stolav.no.
authors.forename: Magnus
authors.initials: M
authors.lastname: Strømmen
authors.affiliation: Department of Clinical Pharmacology, Clinic of Laboratory Medicine, St. Olav University Hospital, Trondheim, Norway; Department of Laboratory Medicine, Children's and Women's Health, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Arne
authors.initials: A
authors.lastname: Helland
authors.affiliation: Centre for Obesity Research, Clinic of Surgery, St. Olav University Hospital, Trondheim, Norway.
authors.forename: Bård
authors.initials: B
authors.lastname: Kulseng
authors.affiliation: Department of Clinical Pharmacology, Clinic of Laboratory Medicine, St. Olav University Hospital, Trondheim, Norway; Department of Laboratory Medicine, Children's and Women's Health, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Olav
authors.initials: O
authors.lastname: Spigset
mesh_terms: D000328:Adult; D050110:Bariatric Surgery; D001682:Biological Availability; D005260:Female; D005743:Gastrectomy / Q000379:methods*; D006556:Heroin Dependence / Q000188:drug therapy; D006801:Humans; D010535:Laparoscopy; D008691:Methadone / Q000493:pharmacokinetics* / Q000627:therapeutic use; D009767:Obesity, Morbid / Q000601:surgery*; D058850:Opiate Substitution Treatment
chemical_list: D008691:Methadone
keywords: bariatric surgery; methadone; opioid replacement; pharmacokinetics