title: Plasma concentrations during naltrexone implant treatment of opiate-dependent patients.
abstract: OBJECTIVE
  To evaluate individual variations in plasma concentrations over time in patients with naltrexone implants.
  
  
  METHODS
  Ten opioid-dependent patients received up to four implants. Plasma samples were collected regularly for the analyses of naltrexone and the metabolite beta-naltrexol.
  
  
  RESULTS
  The median naltrexone C(max) was 12.3 (range 5.8-22.1) ng ml(-1), the median T(max) was 1 day (range 3 h to 35 days), and the median length of time that plasma concentrations were above 1 ng ml(-1) was 55 (range 30-80) days. Two patients reported heroin use without experiencing any effect. Tissue reactions were recorded in two patients after repeated implantation.
  
  
  CONCLUSIONS
  Marked individual and intraindividual variations in naltrexone concentrations were observed. Further studies should be performed to evaluate the need for therapeutic drug monitoring during naltrexone implant treatment.
authors.affiliation: Norwegian Institute of Public Health, Division of Forensic Toxicology and Drug Abuse, PO Box 4404 Nydalen, 0403 Oslo, Norway.
authors.forename: Linda
authors.initials: L
authors.lastname: Olsen
authors.forename: Asbjørg S
authors.initials: AS
authors.lastname: Christophersen
authors.forename: Grete
authors.initials: G
authors.lastname: Frogopsahl
authors.forename: Helge
authors.initials: H
authors.lastname: Waal
authors.forename: Jørg
authors.initials: J
authors.lastname: Mørland
mesh_terms: D000328:Adult; D004343:Drug Implants; D005260:Female; D006801:Humans; D008297:Male; D009270:Naloxone / Q000008:administration & dosage* / Q000097:blood; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000378:metabolism; D009292:Narcotic Antagonists / Q000008:administration & dosage* / Q000097:blood; D009293:Opioid-Related Disorders / Q000534:rehabilitation*
chemical_list: D004343:Drug Implants; D009292:Narcotic Antagonists; D009270:Naloxone; C010410:6 beta-hydroxynaltrexone; D009271:Naltrexone