Continued Naltrexone Use Prevents Opioid Dependency Relapse

Yael Waknine

November 10, 2011

November 10, 2011 — Continued use of once-monthly extended-release naltrexone (NTX) intramuscular injection (Vivitrol, Alkermes plc) is a safe and effective method of preventing relapse to opioid dependency after detoxification, new research suggests.

Findings presented at the 24th Annual US Psychiatric and Mental Health Congress in Las Vegas, Nevada, are a culmination of a year-long open-label extension phase for the original 6-month double-blind study (n = 250) that led to the drug's approval for this indication in October 2010.

As previously reported by Medscape Medical News, data from that study demonstrated that once-monthly use of 380 mg NTX significantly increased the number of abstinence weeks (90% vs 35% for placebo; P = .024) and the likelihood of total abstinence (36% vs 23%; P = .0002).

For the open-label phase, investigators recruited 67 previously treated patients (NTX ⇒ NTX) and 47 other patients who switched from placebo therapy (placebo ⇒ NTX). The majority of patients (n = 71; 62.3%) completed the year-long trial, and about half (n = 58; 50.9%) were completely abstinent, based on urine tests.

Craving for opioids among patients switched from placebo significantly decreased, as evaluated using the Opioid Craving Scale, in which patients rated their "need for opiates" using a visual analog scale ranging from 0 (not at all) to 100 (very much so).

As expected, reducing or stopping opioid use entirely was also associated with improvements in quality of life, as defined by a score of 1 or 2 (very much or much improved) on the Clinical Global Impression–Improvement scale. Responder rates ranged from 80.9% (placebo ⇒ NTX) to 91.0% (NTX ⇒ NTX) for the 6-month phase and 89% (placebo ⇒ NTX) to 97% (NTX ⇒ NTX) during the 1-year extension. Continued treatment through both phases of the study garnered greater improvements.

With respect to Mental Health Component Scores on the Social Functioning and Healthcare Utilization scale, both sets of patients achieved scores of about 50 (placebo ⇒ NTX, 50.0; NTX ⇒ NTX, 50.2), representing the US norm, by the end of the year (baseline scores, 38.1 and 34.8, respectively).

"The robust data from this extension study confirm [extended-release NTX's] efficacy and safety profile over an 18-month period and support its clinical utility as a treatment option for opioid dependence, following opioid detoxification," stated Evgeny Krupitsky, MD, PhD, in a company news release, noting that the drug is the "first and only once-monthly medication that offers patients and physicians a non-narcotic treatment option to help fight this challenging disease."

Dr. Krupitsky is professor of psychiatry at St. Petersburg State Pavlov Medical University and head of the Department of Addictions at the Bekhterev Research Psychoneurological Institute, St. Petersburg, Russia.

As in the original study, adverse events included liver enzyme elevations (gamma-glutamyl transpeptidase, 6.4% - 10.4%; alanine transaminase, 6.4% - 9.0%; and aspartate aminotransferase, 4.3% - 9.0%), with the higher rates observed among those receiving treatment for the extended period. No discontinuations were associated with adverse events. Injection site pain occurred rarely (2.6%), and no serious injection site reactions were observed.

Extended-release NTX is indicated in combination with a comprehensive management system that includes psychosocial support for the prevention of relapse to opioid dependence after opioid detoxification, and the treatment of alcohol dependence in individuals who are able to abstain from imbibing in an outpatient setting.

The study was supported by Alkermes, Inc. The Medisorb preparation used in patients receiving NTX was developed with grants from the National Institute on Drug Abuse and National Institute on Alcohol Abuse and Alcoholism. Dr. Krupitsky is a consultant for Alkermes and received research funding for this study from Alkermes. Three of the researchers are full-time employees of Alkermes, Inc. One researcher is a medical science liaison at Alkermes. One researcher was an unpaid member of the Alkermes advisory board that designed this trial. One researcher has received research supported from Titan Pharmaceuticals, investigator-initiated research funding from Hythiam, and an unrestricted educational grant and speaker support from Reckitt Benckiser.

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