Naltrexone is an opioid receptor antagonist that blocks the euphoric effects of opioids at adequate doses.282 Potential benefits of naltrexone include ease of administration, lack of induced tolerance during long-term treatment, and lack of potential for dependence or non-medical use.283 However, as an opioid antagonist, naltrexone fully blocks the effects of all opioid medications, including opioid analgesics prescribed for pain. Additionally, the reduced tolerance to opioids facilitated by the use of naltrexone increases the risk of overdose for patients who stop taking the medication and subsequently relapse to opioid use, as demonstrated by a non-randomized study of oral naltrexone-associated mortality rates that were three to seven times higher than methadone-related mortality rates in Australia.284 

Oral naltrexone has been shown to have limited benefits over placebo.285 For example, a 2011 meta-analysis found no statistically significant differences in retention or abstinence rates for oral naltrexone compared to placebo or no treatment.285 The only outcome that favoured oral naltrexone over placebo was reduced re-incarceration rates, but this finding was limited to 2 of the 13 randomized trials included in the review.285 Based on limited data, review authors also concluded that oral naltrexone was not superior to psychotherapy alone (two studies), benzodiazepine-based treatment (one study), or buprenorphine monotherapy (one study) in terms of retention in treatment, abstinence from opioid use, and reported side effects.285 Across studies, treatment retention rates were low with oral naltrexone treatment (28%).285 Of note, a single randomized trial published subsequent to the meta-analysis reported a significantly higher proportion of opioid-negative urine tests among individuals on oral naltrexone (42.7%) compared to placebo (34.1%).286

A 2019 study randomized patients to continue oral naltrexone (n=32) or switch to extended-release naltrexone (n=28) following medication-assisted detoxification and a 50mg naltrexone challenge. Individuals randomized to extended-release naltrexone were retained in treatment for 6 months at over twice the rate of those on oral naltrexone (57.1% vs. 28.1%).287 

Oral naltrexone is a regular benefit medication for patients enrolled in Fair PharmaCare, Plan B (Licensed Residential Care Facilities), Plan C (Income Assistance), Plan G (Psychiatric Medications), and Plan W (First Nations Health Benefits).  Note that Fair PharmaCare coverage is income-based, and eligible costs may be subject to a deductible.