New York—The safety and effectiveness of two medications for treating opioid addiction are similar in helping patients end opioid use, avoid relapses, stay with the program, and elude overdoses. The catch, according to a new study, is in initiating the treatment.

A study published in The Lancet, determined that extended-release naltrexone demonstrated similar safety and clinical effectiveness to more commonly prescribed buprenorphine-naloxone. 

New York University School of Medicine–led researchers point out, however, that patients being treated with naltrexone, an opioid antagonist marketed as Vivitrol, must detoxify before the drug can be administered—which is commonly called the “detox hurdle.”

On the other hand, buprenorphine, an opioid agonist marketed both generically and as branded Suboxone, allows a transition from opioid use to medication maintenance without a detoxification requirement.

While similarly effective, the two drugs have stark differences, which study authors list here:
• Agonists activate opioid receptors, have opioid-like effects, and maintain physical dependence on opioids, while antagonists have no effects on their own and block the effects of opioids.
• Agonists can be initiated while a patient is still opioid dependent or detoxifying, but antagonists only can be administered after full detoxification to avoid opioid withdrawals.
• When discontinued, agonists are associated with withdrawal symptoms; antagonists are not.
• Agonists have abuse potential and diversion risks; antagonists do not.
• Prescribing regulations and community acceptance differ.

Participants in the study, which was conducted at eight sites within the National Institute on Drug Abuse Clinical Trials Network (NIDA CTN), were dependent on nonprescribed opioids—82% were heroin users and 16% were on pain medications. The 570 opioid-dependent adults were randomized to the buprenorphine combination or the naltrexone formulation, and followed for up to 24 weeks of outpatient treatment. Buprenorphine/naloxone was administered daily as a sublingual film, while naltrexone was a monthly intramuscular injection. 

“Studies show that people with opioid dependence who follow detoxification with no medication are very likely to return to drug use, yet many treatment programs have been slow to accept medications that have proven to be safe and effective,” explained Nora D. Volkow, MD, director of NIDA. “These findings should encourage clinicians to use medication protocols, and these important results come at a time when communities are struggling to link a growing number of patients with the most effective individualized treatment.”

Results indicate that, as expected, fewer patients could successfully initiate naltrexone compared to buprenorphine/naloxone—72.1% versus 94.1%, which led to slightly higher relapse rates for naltrexone—65.4% versus 56.8% over 24 weeks.

Yet, among the 474 participants successfully started on medication, the 24-week relapse rates were similar—52.0% for naltrexone versus 55.6% for buprenorphine/naloxone. While other opioid use outcomes—days abstinent, negative urine tests, and time-to-relapse—were slightly better for buprenorphine/naloxone than naltrexone for the full sample of 570 participants, that was reversed for patients who actually initiated treatment, the study notes.

“As the epidemic has escalated, and hundreds of people in the U.S. and elsewhere are dying every day, there is an increased urgency to provide immediate and effective medical treatment,” emphasized senior author John Rotrosen, MD, professor in the Department of Psychiatry at NYU School of Medicine.  “Our findings should dispel some commonly held misconceptions and help patients choose between these different approaches to treatment.”
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