title: Are take-home naloxone programmes effective? Systematic review utilizing application of the Bradford Hill criteria.
abstract: Fatal outcome of opioid overdose, once detected, is preventable through timely administration of the antidote naloxone. Take-home naloxone provision directly to opioid users for emergency use has been implemented recently in more than 15 countries worldwide, albeit mainly as pilot schemes and without formal evaluation. This systematic review assesses the effectiveness of take-home naloxone, with two specific aims: (1) to study the impact of take-home naloxone distribution on overdose-related mortality; and (2) to assess the safety of take-home naloxone in terms of adverse events.
  
  
  
  PubMed, MEDLINE and PsychINFO were searched for English-language peer-reviewed publications (randomized or observational trials) using the Boolean search query: (opioid OR opiate) AND overdose AND prevention. Evidence was evaluated using the nine Bradford Hill criteria for causation, devised to assess a potential causal relationship between public health interventions and clinical outcomes when only observational data are available.
  
  
  
  A total of 1397 records (1164 after removal of duplicates) were retrieved, with 22 observational studies meeting eligibility criteria. Due to variability in size and quality of the included studies, meta-analysis was dismissed in favour of narrative synthesis. From eligible studies, we found take-home naloxone met all nine Bradford Hill criteria. The additional five World Health Organization criteria were all either met partially (two) or fully (three). Even with take-home naloxone administration, fatal outcome was reported in one in 123 overdose cases (0.8%; 95% confidence interval = 0.4, 1.2).
  
  
  
  Take-home naloxone programmes are found to reduce overdose mortality among programme participants and in the community and have a low rate of adverse events.
authors.affiliation: National Addiction Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: McDonald
authors.affiliation: National Addiction Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors.forename: John
authors.initials: J
authors.lastname: Strang
mesh_terms: D000701:Analgesics, Opioid / Q000506:poisoning*; D062787:Drug Overdose / Q000188:drug therapy* / Q000401:mortality; D006801:Humans; D009270:Naloxone / Q000627:therapeutic use*; D009292:Narcotic Antagonists / Q000627:therapeutic use*; D009293:Opioid-Related Disorders
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009270:Naloxone
keywords: Bradford Hill; death; heroin; naloxone; opiate; opioid; overdose; prevention