title: Low-dose naltrexone and opioid consumption: a drug utilization cohort study based on data from the Norwegian prescription database.
abstract: OBJECTIVE
  Low-dose naltrexone (LDN) is used in a wide range of conditions, including chronic pain and fibromyalgia. Because of the opioid antagonism of naltrexone, LDN users are probably often warned against concomitant use with opioids. In this study, based on data from the Norwegian prescription database, we examine changes in opioid consumption after starting LDN therapy.
  
  
  METHODS
  We included all Norwegian patients (N = 3775) with at least one recorded LDN prescription in 2013 and at least one dispensed opioid prescription during the 365 days preceding the first LDN prescription. We allocated the patients into three subgroups depending on the number of collected LDN prescriptions and recorded the number of defined daily doses (DDDs) on collected prescriptions on opioids, nonsteroidal anti-inflammatory drugs and other analgesics and antipyretics from the same patients.
  
  
  RESULTS
  Among the patients collecting ≥4 LDN prescriptions, annual average opioid consumption was reduced by 41 DDDs per person (46%) compared with that of the previous year. The reduction was 12 DDDs per person (15%) among users collecting two to three prescriptions and no change among those collecting only one LDN prescription. We observed no increase in the number of DDDs in nonsteroidal anti-inflammatory drugs or other analgesics and antipyretics corresponding to the decrease in opioid use.
  
  
  CONCLUSIONS
  Possibly, LDN users avoided opioids because of warnings on concomitant use or the patients continuing on LDN were less opioid dependent than those terminating LDN. Therapeutic effects of LDN contributing to lower opioid consumption cannot be ruled out. © 2017 The Authors. Pharmacoepidemiology & Drug Safety Published by John Wiley & Sons Ltd.
authors.affiliation: Regional Medicines Information and Pharmacovigilance Centre (RELIS), University Hospital of North Norway, Tromsø, Norway.|National Centre for Emergency Primary Health Care, Uni Research Health, Bergen, Norway.
authors.forename: Guttorm
authors.identifier: http://orcid.org/0000-0002-3376-6761
authors.initials: G
authors.lastname: Raknes
authors.affiliation: Department of Pharmacy, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway.
authors.forename: Lars
authors.identifier: http://orcid.org/0000-0001-6475-3368
authors.initials: L
authors.lastname: Småbrekke
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D015331:Cohort Studies; D016208:Databases, Factual / Q000639:trends*; D011307:Drug Prescriptions; D004363:Drug Utilization / Q000639:trends*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009271:Naltrexone / Q000008:administration & dosage*; D009292:Narcotic Antagonists / Q000008:administration & dosage*; D009664:Norway / Q000453:epidemiology
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009271:Naltrexone
keywords: drug utilization; naltrexone; off label prescribing; opioids; painkillers; pharmacoepidemiology; prescription database