title: Buprenorphine maintenance and mu-opioid receptor availability in the treatment of opioid use disorder: implications for clinical use and policy.
abstract: BACKGROUND
  Sublingual formulations of buprenorphine (BUP) and BUP/naloxone have well-established pharmacokinetic and pharmacodynamic profiles, and are safe and effective for treating opioid use disorder. Since approvals of these formulations, their clinical use has increased. Yet, questions have arisen as to how BUP binding to mu-opioid receptors (μORs), the neurobiological target for this medication, relate to its clinical application. BUP produces dose- and time-related alterations of μOR availability but some clinicians express concern about whether doses higher than those needed to prevent opioid withdrawal symptoms are warranted, and policymakers consider limiting reimbursement for certain BUP dosing regimens.
  
  
  METHODS
  We review scientific data concerning BUP-induced changes in μOR availability and their relationship to clinical efficacy.
  
  
  RESULTS
  Withdrawal suppression appears to require ≤50% μOR availability, associated with BUP trough plasma concentrations ≥1 ng/mL; for most patients, this may require single daily BUP doses of 4 mg to defend against trough levels, or lower divided doses. Blockade of the reinforcing and subjective effects of typical doses of abused opioids require <20% μOR availability, associated with BUP trough plasma concentrations ≥3 ng/mL; for most individuals, this may require single daily BUP doses >16 mg, or lower divided doses. For individuals attempting to surmount this blockade with higher-than-usual doses of abused opioids, even larger BUP doses and <10% μOR availability would be required.
  
  
  CONCLUSIONS
  For these reasons, and given the complexities of studies on this issue and comorbid problems, we conclude that fixed, arbitrary limits on BUP doses in clinical care or limits on reimbursement for this care are unwarranted.
authors.affiliation: Department of Psychiatry and Behavioral Neurosciences, School of Medicine, and Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Tolan Park Medical Building, Suite 2A, 3901 Chrysler Service Drive, Detroit, MI 48201, USA. Electronic address: mgreen@med.wayne.edu.
authors.forename: Mark K
authors.initials: MK
authors.lastname: Greenwald
authors.affiliation: Division on Substance Abuse, New York State Psychiatric Institute and Department of Psychiatry, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA.
authors.forename: Sandra D
authors.initials: SD
authors.lastname: Comer
authors.affiliation: Department of Internal Medicine Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Fiellin
mesh_terms: D000286:Administration, Sublingual; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000378:metabolism; D002047:Buprenorphine / Q000008:administration & dosage* / Q000378:metabolism; D006291:Health Policy / Q000639:trends; D006801:Humans; D009270:Naloxone / Q000008:administration & dosage / Q000378:metabolism; D058850:Opiate Substitution Treatment / Q000379:methods*; D009293:Opioid-Related Disorders / Q000188:drug therapy* / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D017450:Receptors, Opioid, mu; D009270:Naloxone; D002047:Buprenorphine
keywords: Buprenorphine; Opioid dependence; Opioid receptors; Policy; Positron emission tomography; Treatment