Use of Naltrexone by Opiod Addicts
If you've ever injected Naloxone into someone having an opioid overdose, you never forget it. Naloxone blocks the receptor in the brain that gives opiates their punch and puts the patient into immediate full-blown withdrawal. It's life-saving but rough - think that scene from Trainspotting.
Naltrexone is Naloxone longer-acting cousin. The oral formulation has a half-life of around four hours and there have been several studies examining the use of this drug to treat opiate addiction, but overall, the results have been disappointing, skipping a dose is simply too easy. But we may have a new weapon in the fight against opioid abuse in the form of extended release Naltrexone - a depo injection that lasts roughly a month.
A randomized trial appearing in the New England Journal of Medicine examined the efficacy of this agent in a group of previously incarcerated individuals with opioid dependence. Needless to say, this group is at high risk of relapse. In this open-label trial 153 individuals received monthly injections of extended release now tracks own for six months and 155 received what you might call usual care - basically counseling and referral to community support programs. The primary outcome was time to relapse and relapse rates were high. Forty-three percent in the extended release naltrexone group and sixty-four percent in the usual care group. Still that difference translates into a number needed to treat of five. Meaning this drug is actually pretty efficacious though time to relapse was the primary outcome. I was more interested in some of the ancillary measures. For instance, there was no difference in the re-incarceration rate in the two groups both were around twenty-five percent.
Naltrexone has also been advocated as a drug that might curb binge drinking but there was no difference in self-reported heavy drinking which occurred in about fifteen percent of both groups after six months Naltrexone injections were stopped. But the participants were followed out for a year after that without the injections the relapse rate in the treatment group quickly caught up with the usual care group. This drug may be a long-term proposition. Fortunately, there were no overdose events in the treatment group even after treatment ended. This is a critical finding. As there's a theoretical concern that treatment with Naltrexone might condition individuals to take higher doses of opioids when Naltrexone is stopped those higher doses can be fatal. That this effect wasn't seen shooting courage those of us who might want to use this agent in clinical practice.
I should point out that extended-release Naltrexone was not compared to what many consider the more standard approach to therapy namely buprenorphine or methadone maintenance though that trial is proceeding apace. In the meantime, this is what we have and with the epidemic of opioid addiction growing worse by the day I for one I'm glad to have one more weapon in the fight.