Extended-release injectable naltrexone is a long-acting opioid antagonist given by injection about once every four weeks. It is FDA-approved for opioid use disorder after opioid detoxification and for alcohol use disorder in appropriate patients. It blocks opioid receptors rather than activating them.
How does extended-release naltrexone work?
Naltrexone binds to opioid receptors and blocks the euphoric and sedating effects of opioids. It does not produce an opioid “high” and does not cause opioid physical dependence.
How is injectable naltrexone different from buprenorphine or methadone?
Buprenorphine and methadone activate opioid receptors to different degrees and can directly suppress opioid withdrawal and cravings. Naltrexone blocks opioid receptors and therefore cannot be started while opioids are still active in the body.
Trinity’s comparison of naltrexone versus buprenorphine explains the difference in more detail.
Why is an opioid-free period required first?
If naltrexone is given while a person is physically dependent on opioids, it can trigger precipitated withdrawal. SAMHSA states that patients generally need at least 7 days after short-acting opioids and 10 to 14 days after long-acting opioids before starting naltrexone, although the actual plan should be individualized.
How long does one injection last?
The extended-release formulation is designed to provide medication over about four weeks. Follow-up injections are scheduled monthly when treatment continues.
Can extended-release naltrexone be used for alcohol use disorder?
Yes. The injectable formulation is FDA-approved for alcohol use disorder as well as opioid use disorder. It can reduce alcohol-related reward and cravings for some people.
What are important risks?
People should not try to overcome naltrexone’s opioid blockade by taking large amounts of opioids. That can result in serious or fatal overdose. After naltrexone wears off or is discontinued, opioid tolerance may also be lower, which increases overdose risk if opioid use resumes.
Clinicians also consider liver health, injection-site reactions, current medications, pregnancy status when relevant, and other medical factors before treatment.
Can someone receive injectable naltrexone during residential rehab?
Potentially, if it is clinically appropriate and the facility can provide or coordinate the medication. A person with opioid use disorder must complete the required opioid-free period first.
Trinity Behavioral Health provides information about adult residential addiction treatment. This article does not state that Trinity currently offers extended-release naltrexone; availability should be verified directly.
Frequently asked questions
Is extended-release naltrexone an opioid?
No. It is an opioid antagonist.
Can it be used while someone is taking buprenorphine or methadone?
No. Starting naltrexone while opioid agonists are still active can precipitate withdrawal.
Does the injection cure opioid use disorder?
No. It is one evidence-based treatment option and is usually part of a broader recovery plan.
Does injectable naltrexone cause withdrawal when stopped?
No opioid withdrawal is expected from stopping naltrexone itself because it is not an opioid agonist.
Sources
- SAMHSA: Naltrexone
- SAMHSA TIP 63: Medications for Opioid Use Disorder
- FDA: Approved Drug Labeling Resources
This article is general educational information and does not replace individualized medical advice.