What Is Vivitrol?

Vivitrol is the brand name for naltrexone extended-release injectable suspension—a once-monthly injection used in the treatment of both opioid use disorder (OUD) and alcohol use disorder (AUD). Unlike buprenorphine-based medications such as Suboxone or Sublocade, Vivitrol contains no opioids whatsoever. It works by a completely different mechanism: blocking opioid receptors rather than activating them. This makes Vivitrol the only FDA-approved monthly injection for addiction treatment that is entirely opioid-free and non-controlled.

Vivitrol is manufactured by Alkermes and delivered as a 380 mg intramuscular (IM) injection into the gluteal muscle, administered once every four weeks by a healthcare provider. The extended-release formulation uses Alkermes’ proprietary microsphere technology to provide sustained naltrexone levels for the full month between injections.

Vivitrol for Opioid Use Disorder

For patients with opioid use disorder, Vivitrol works by competitively binding to mu, kappa, and delta opioid receptors throughout the central nervous system. When naltrexone occupies these receptors, opioids such as heroin, oxycodone, or fentanyl cannot bind and produce their euphoric or pain-relieving effects. In practical terms: if a patient on Vivitrol uses an opioid, they will feel little to no effect. The reward response that drives continued use is eliminated.

Key benefits for OUD treatment include:

• Blocks opioid effects completely: Unlike partial agonist therapies, naltrexone provides full blockade. A patient on Vivitrol who uses opioids will not get high, removing much of the incentive for use.
• Non-addictive, non-controlled: Vivitrol is not an opioid and carries no potential for misuse, dependence, or diversion. There is nothing to “abuse” in the traditional sense.
• Once-monthly convenience: The injection format eliminates the challenge of daily medication compliance and removes medication from the home entirely.
• No tolerance or dose escalation: Unlike opioid agonist therapies, naltrexone does not require dosage adjustments over time for most patients.

Vivitrol for Alcohol Use Disorder

Vivitrol’s utility extends well beyond opioid addiction—it is also FDA-approved and highly effective for alcohol use disorder. The mechanism here is nuanced: alcohol indirectly stimulates the brain’s opioid system, contributing to alcohol’s rewarding and pleasurable effects. By blocking opioid receptors, naltrexone blunts the euphoria and craving response triggered by drinking. This reduces the drive to drink and, for many patients, makes it easier to stop after one drink rather than continuing to a full relapse.

For patients with AUD, Vivitrol can:

• Reduce the number of heavy drinking days per month
• Decrease total alcohol consumption even when some drinking occurs
• Support sustained abstinence when combined with counseling
• Reduce relapse rates compared to placebo in clinical trials

This dual indication—treating both opioid and alcohol use disorders—makes Vivitrol particularly valuable for patients with polysubstance use histories involving both alcohol and opioids.

Critical Requirement: Opioid-Free Period Before Starting

The most important safety consideration with Vivitrol for opioid use disorder patients is the required opioid-free period before starting treatment. Because naltrexone is an opioid antagonist, administering it to a patient with any opioid dependence will precipitate sudden, severe withdrawal—a deeply uncomfortable and potentially dangerous experience.

Patients must be completely opioid-free for 7 to 14 days before receiving their first Vivitrol injection. The exact duration depends on the opioids involved:

• Short-acting opioids (heroin, oxycodone, hydrocodone): minimum 7–10 days opioid-free
• Methadone or buprenorphine (long-acting): minimum 10–14 days, often longer for methadone
• Fentanyl (which accumulates in tissue): may require extended opioid-free periods; close clinical monitoring is warranted

Dr. Agresti may use a naloxone challenge test prior to the first injection to confirm that the patient is fully opioid-free before administering Vivitrol. This precaution protects your safety and ensures the first injection goes smoothly.

For patients transitioning from Suboxone or Sublocade, a medically supervised taper and opioid-free window is required before Vivitrol can begin. Dr. Agresti will guide this transition process carefully.

How Vivitrol Blocks Opioid Receptors

Naltrexone is a competitive opioid antagonist with a strong binding affinity for opioid receptors—significantly higher than most opioid agonists. When naltrexone is present at the receptor, it displaces opioids and prevents them from binding. This blockade is not absolute at very high opioid doses (such as massive fentanyl overdoses), but at typical street doses the blockade is functionally complete.

Unlike buprenorphine, which is a partial agonist and produces some opioid receptor activity, naltrexone produces zero agonist activity. It simply occupies the receptor and leaves. This means:

• No opioid “buzz” or mood elevation from naltrexone itself
• No physical dependence on naltrexone
• No withdrawal syndrome when naltrexone is discontinued
• The medication can be stopped at any time without a taper

Oral Naltrexone vs. Vivitrol: Why the Injection Matters

Naltrexone has been available as a daily oral pill (50 mg) since the 1980s. While effective when taken consistently, oral naltrexone has a well-documented adherence problem: patients who are ambivalent about sobriety simply stop taking the pill when cravings hit. A patient who stops oral naltrexone on Monday can be using opioids by the weekend.

Vivitrol’s extended-release injection solves this problem:

Clinical studies consistently show that Vivitrol achieves superior treatment outcomes compared to oral naltrexone, largely due to this adherence advantage. When the medication is on board, it works. Vivitrol ensures the medication stays on board.

Is Vivitrol Right for You?

Vivitrol may be the right choice if you:

• Are highly motivated to abstain from opioids and are willing to complete the required opioid-free period
• Prefer an opioid-free treatment approach (no buprenorphine or methadone)
• Have alcohol use disorder—either alone or co-occurring with opioid use disorder
• Are in a professional environment where being on a controlled substance is a concern (law enforcement, certain healthcare roles, etc.)
• Have previously completed detox and want relapse prevention support
• Have struggled with adherence to daily oral medications

Schedule a Consultation with Dr. Agresti

Dr. Mark G. Agresti is a board-certified psychiatrist serving Palm Beach and greater South Florida with expertise in addiction medicine. Whether you are weighing Vivitrol against buprenorphine-based therapies or have already completed detox and are ready to start, Dr. Agresti will guide you through all your options and help you build a sustainable recovery plan.

Office: 44 Cocoanut Row, Suite M-202, Palm Beach, FL 33480
Phone: 561-760-4107
After-hours emergency: 561-386-7743

Learn more about related services:

• Medication-Assisted Treatment Overview
• Outpatient Detox & Addiction Treatment
• Telehealth Psychiatric Treatment in Florida