# 27 - Naltrexone in relapse prevention

# Naltrexone in relapse prevention

Addictions and substance misuse
CHAPTER 4
Opioid withdrawal in a specialist addiction in-­patient setting
Methadone
Patients should have a starting dose assessment of methadone over 48 hours by a 
­specialist in-­patient team. The dose may then be reduced following a linear regimen over 
up to 4 weeks.86
Buprenorphine
Buprenorphine can be used effectively for short-­term in-­patient detoxifications following the same principles as for methadone.
Naltrexone in relapse prevention
Trial evidence for the effectiveness of either oral or sustained-­release naltrexone as a 
treatment for relapse prevention in opioid misusers has been inconclusive.89,90 
Naltrexone was found by NICE to be a cost-­effective treatment strategy in aiding abstinence from opioid misuse for those who prefer an abstinence programme, are fully 
informed of the potential adverse effects and benefits of treatment, are highly motivated 
to remain on treatment, and have a partner supporting concordance.91 Subsequently, 
Australian data indicated a threefold risk of mortality relative to methadone treatment 
following naltrexone cessation.92 Almost all of the excess mortality was associated with 
overdose deaths after stopping naltrexone.
Close monitoring is particularly important when naltrexone is initiated because of the 
higher risk of fatal overdose at this and other times. Discontinuation of naltrexone is also 
associated with an increase in inadvertent overdose from illicit opioids. Postmortem data 
from Australia found that only 15.8% of those prescribed oral naltrexone had any naltrexone detected.93 Thus, supervision of naltrexone administration and careful choice of 
who is prescribed it (those who are abstinence-­focused and motivated) are very important. 
Although there have been concerns about people taking naltrexone experiencing adverse 
effects of unease (dysphoria), depression and insomnia, potentially leading to relapse to 
illicit opioid use or failure to continue on treatment, real-­world evidence is mixed, with 
two studies finding no effect of naltrexone on mood and sleep94,95 and one finding higher 
insomnia and distress in those patients who discontinued naltrexone.96
Initiating naltrexone
Naltrexone has the propensity to cause a severe withdrawal reaction in patients who are 
either currently taking opioid drugs or who were previously taking opioid drugs and in 
whom there has not been a sufficient wash-­out period before administering naltrexone.
Table 4.19  A suggested reduction regimen for buprenorphine.
Daily buprenorphine dose
Reduction rate
Above 16mg
4mg every 1–2 weeks
8–16mg
2–4mg every 1–2 weeks
2–8mg
2mg per week or fortnight
Below 2mg
0.4–0.8mg per week