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Switching to naltrexone does not increase pain in opioid dependence

Lars Tanum

Switching from buprenorphine-naloxone to extended-release naltrexone did not induce or increase pain in people with opioid use disorder during long-term treatment, according to a study published in American Journal of Addiction.

“Prior research has shown that extended-release naltrexone shows promise for treating opioid dependence, but no study has examined how this treatment impacts long-term pain conditions, ” Lars Tanum, MD, PhD, from the department of research & development in mental health, Akershus University Hospital, and the Norwegian Center for Addiction Research, University of Oslo, Norway, and colleagues wrote.

In this randomized prospective open-label clinical study, researchers evaluated changes in pain among 143 Norwegian adults with opioid dependence receiving treatment with either extended-release naltrexone hydrochloride or buprenorphine-naloxone hydrochloride.

After opioid detoxification, patients received 12-week treatment with either long-acting naltrexone (380 mg intramuscularly injected every 4 weeks) or buprenorphine naloxone (flexible 4 mg to 16 mg sublingual doses daily). Then, participants were followed in a 9-month open-treatment study with the participant’s choice of either naltrexone or buprenorphine-naloxone. The researchers examined changes in pain every 4 weeks via the Norwegian Short-Form of McGill Pain Questionnaire.

There was no increase in sensory pain, affective pain or present pain intensity as measured by the McGill Pain Questionnaire in either treatment group throughout the 12-week period. In addition, Tanum and colleagues found no increase in subgroups with chronic pain.

In the follow-up phase, 117 participants chose naltrexone. During longer-term treatment, those who switched from buprenorphine-naloxone to extended-release naltrexone reported no increase in pain intensity. In addition, the results showed no significant improvement in pain score over time, in terms of mean sensory, affective, present pain intensity and visual analogue scale scores within the naltrexone maintenance and switch groups. Pain did not differ between the maintenance and switch groups.

Tanum and colleagues also found that men experienced less affective pain than women, and participants with hepatitis C reported mild-to-moderate pain more frequently than low or no pain.

“Our present results improve our understanding of the role of opioid receptors in chronic pain. Overall, our present results challenge the perceived notion that an opioid antagonist, such as [extended-release naltrexone], is likely to aggravate longstanding pain in individuals with opioid dependencies,” they wrote. “Our findings also raise questions regarding whether opioids can provide adequate analgesic efficacy in individuals with opioid dependencies who experience chronic mild-to-moderate pain.”

Disclosure: The authors report no relevant financial disclosures.