The injectable extended-release formulation of naltrexone, marketed as Vivitrol, has been approved as a treatment for preventing relapses in people who have undergone opioid detoxification, the Food and Drug Administration announced.
Vivitrol, which was approved in 2006 for the treatment of alcohol dependence, is administered in an intramuscular injection once a month, in patients who have no opioids remaining in their system.
If opioids are present, patients may experience withdrawal symptoms, according to the FDA statement. Naltrexone is an opioid antagonist.
Approval was based on the results of a 6-month study of 250 patients who were completing or had recently completed detoxification and were no longer physically dependent on opioids.
Between the 5th week and the end of the study, 36% of those treated with Vivitrol (one 380-mg injection once a month) had not used opioids at all, compared with 23% of those on placebo, a significant difference. All patients received psychosocial support during the study.
Side effects associated with Vivitrol treatment include nausea, fatigue, headache, dizziness, vomiting, reduced appetite, painful joints, and muscle cramps, the FDA statement said.
Serious side effects include injection site reactions, allergic reactions, hepatotoxicity, and depression, as well as suicide and suicidal thoughts and behavior.
Customized needles provided in the Vivitrol package must be used to inject the medication as an intramuscular gluteal injection, according to the FDA and Alkermes Inc., the manufacturer of Vivitrol.
The FDA has asked the company to conduct postmarketing pharmacokinetic and efficacy studies of Vivitrol in patients aged 12-16 years.
Serious adverse reactions associated with Vivitrol should be reported to the FDA's MedWatch program at 800-332-1088 or www.fda.gov/medwatch