Challenges to antagonist blockade during sustained-release naltrexone treatment.
OBJECTIVE
Naltrexone is a competitive opioid antagonist that effectively blocks the action of heroin and other opioid agonists. Sustained-release naltrexone formulations are now available that provide long-acting opioid blockade. This study investigates the use of heroin and other opioids among opioid-dependent patients receiving treatment with long-acting naltrexone implants, their subjective experience of drug 'high' after opioid use, and factors associated with opioid use.


METHODS
Participants (n = 60) were opioid-dependent patients receiving treatment with naltrexone implants. Outcome data on substance use, drug 'high', depression and criminal activity were collected over a 6-month period. Blood samples were taken to monitor naltrexone plasma levels, and hair samples to verify self-reported opioid use.


RESULTS
More than half [n = 34 or 56%; 95% confidence interval (CI) 44-68%)] the patients challenged the blockade with illicit opioids during the 6-month treatment period; 44% (n = 26; 95% CI 32-56%) were abstinent from opioids. Mean opioid use was reduced from 18 [standard deviation (SD)13] days during the month preceding treatment to 6 days (SD 11) after 6 months. Of the respondents questioned on opioid 'high' (n = 31), nine patients (30%; 95% CI 16-47%) reported partial drug 'high' following illicit opioid use, and three (12%; 95% CI 3-26%) reported full 'high'. Opioid use was associated with use of non-opioid drugs and criminal behaviour.


CONCLUSIONS
Challenging naltrexone blockade with heroin on at least one occasion is common among sustained-release naltrexone patients, but only a minority of patients use opioids regularly. Challenges represent a warning sign for poor outcomes and often occur in the context of polydrug use and social adjustment problems.
Kunøe
Nikolaj
N
SERAF, Norwegian Centre for Addiction Research, Kirkeveien 166, 0407 Oslo, Norway. nikolaj.kunoe@medisin.uio.no
Lobmaier
Philipp
P
Vederhus
John Kåre
JK
Hjerkinn
Bjørg
B
Gossop
Michael
M
Hegstad
Solfrid
S
Kristensen
Øistein
Ø
Waal
Helge
H
D000328:Adult; D003415:Crime; D003692:Delayed-Action Preparations; D003863:Depression / Q000453:epidemiology; D004343:Drug Implants; D062787:Drug Overdose; D005059:Euphoria; D005260:Female; D006197:Hair / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D009271:Naltrexone / Q000493:pharmacokinetics / Q000627:therapeutic use*; D009292:Narcotic Antagonists / Q000493:pharmacokinetics / Q000627:therapeutic use*; D009294:Narcotics / Q000494:pharmacology / Q000506:poisoning*; D009293:Opioid-Related Disorders / Q000523:psychology / Q000534:rehabilitation*; D010349:Patient Compliance; D011569:Psychiatric Status Rating Scales; D055502:Secondary Prevention; D015813:Substance Abuse Detection; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy; D016896:Treatment Outcome; D055815:Young Adult
D003692:Delayed-Action Preparations; D004343:Drug Implants; D009292:Narcotic Antagonists; D009294:Narcotics; D009271:Naltrexone