Naltrexone and Vivitrol in Addiction Treatment: Uses and Eligibility

Naltrexone is one of the few medications in addiction medicine with a decades-long track record for both opioid use disorder and alcohol use disorder — a dual-purpose profile that sets it apart from most other pharmacological tools in this space. It comes in two forms: a daily oral tablet and an extended-release injectable formulation marketed as Vivitrol. The distinction between those two delivery methods turns out to matter quite a bit in practice — clinically, logistically, and in terms of who can actually benefit from each.

Definition and scope

Naltrexone belongs to the opioid antagonist class of medications. Unlike methadone or buprenorphine, which are themselves opioids, naltrexone contains no opioid properties whatsoever — it works purely by blocking opioid receptors rather than activating them. The FDA approved oral naltrexone for opioid use disorder in 1984 and for alcohol use disorder in 1994. Vivitrol, the injectable form, received FDA approval for alcohol dependence in 2006 and for opioid use disorder in 2010 (FDA, Vivitrol prescribing information).

That timeline matters because it explains why Vivitrol is the newer, more studied option in the injectable category, and why its evidence base for opioid use disorder is still being refined. Both formulations are classified as non-scheduled medications under the Controlled Substances Act, meaning no special DEA waiver is required to prescribe them — a meaningful contrast with buprenorphine, which carried prescribing restrictions until the federal X-waiver requirement was eliminated in 2023.

How it works

Naltrexone binds to mu-opioid receptors — the same receptors that opioids like heroin, fentanyl, and oxycodone target — and blocks them competitively. When those receptors are occupied by naltrexone, opioids taken afterward produce little to no euphoric effect. The same receptor-blocking mechanism extends to the endorphin release triggered by alcohol, which is part of why alcohol cravings and consumption drop in patients who take it consistently.

The pharmacology is clean: naltrexone itself produces no high, no physical dependence, and no withdrawal syndrome when stopped. That's the appeal. The challenge is adherence, which is exactly what Vivitrol was designed to address.

Vivitrol delivers 380 mg of extended-release naltrexone in a single monthly intramuscular injection, maintaining therapeutic blood levels across the full 30-day window (SAMHSA, Naltrexone Overview). Oral naltrexone is typically prescribed at 50 mg per day. The clinical difference between those two options isn't just convenience — it's the difference between "did this person take their medication today" and "this person is pharmacologically covered for the month."

Common scenarios

Naltrexone is used across a range of treatment settings, from outpatient primary care to residential programs — a breadth that reflects its flexible prescribing profile. The how drug rehab works often determines which form makes practical sense.

Three situations where naltrexone appears frequently:

1. Post-acute care transition for opioid use disorder. Someone completing detoxification or a residential stay may be started on Vivitrol before discharge, precisely because the post-treatment window carries elevated relapse and overdose risk. A 380 mg injection at discharge provides 30 days of receptor blockade without relying on daily pill-taking habits that haven't yet been established.

2. Alcohol use disorder in outpatient settings. Oral naltrexone has strong evidence here — a 2006 meta-analysis published in the Archives of General Psychiatry found it reduced the risk of heavy drinking by approximately 83% compared to placebo in some trial populations. It is often prescribed alongside counseling without requiring the kind of specialized addiction infrastructure associated with methadone clinics.

3. Patients motivated to avoid opioid agonist therapies. Some individuals, for personal, occupational, or philosophical reasons, prefer a non-opioid approach. Naltrexone is the only option in that category with FDA approval for opioid use disorder.

Exploring the key dimensions and scopes of drug rehab helps clarify how medication-assisted treatment fits within the broader continuum of care.

Decision boundaries

Naltrexone is not universally appropriate, and the eligibility requirements are specific rather than vague.

The critical prerequisite: patients must be fully opioid-free before starting naltrexone — typically for a minimum of 7 to 10 days for short-acting opioids and 10 to 14 days for methadone. Administering naltrexone before opioids have cleared the system will precipitate acute opioid withdrawal, which is medically uncomfortable and can be severe. This is not a mild caution; it's the primary clinical barrier to naltrexone initiation.

Liver function considerations: Naltrexone is processed hepatically, and it carries a boxed warning for hepatotoxicity at doses substantially above the therapeutic range. Patients with acute hepatitis or liver failure are generally not candidates. Those with elevated liver enzymes are evaluated case by case.

Who tends to do better on Vivitrol vs. oral naltrexone:

• Vivitrol: Stronger fit for patients with lower medication adherence, those in early recovery with high relapse vulnerability, or those in institutional transitions (e.g., leaving incarceration or residential care).
• Oral naltrexone: Better suited to patients with high motivation and established daily routines, or those in settings where monthly injections aren't logistically accessible.

Neither form is a standalone treatment. SAMHSA's Treatment Improvement Protocol 49 explicitly frames medication-assisted treatment as most effective when combined with behavioral interventions. The how to get help for drug rehab page outlines pathways for connecting with providers who prescribe these medications.

For broader questions about addiction treatment structure, the drug rehab frequently asked questions page addresses common concerns about medication, cost, and program types.