The Vivitrol Induction Appointment: What to Expect

Extended-release naltrexone — the brand name most people know is Vivitrol — is one of three FDA-approved medications for opioid use disorder, alongside methadone and buprenorphine. It does not get anyone high and it does not create physical dependence; instead it blocks opioid receptors for about four weeks at a time so that using opioids during that window produces little or no effect. Roughly 5.7 million people in the U.S. were living with opioid use disorder as of 2023, and the medication most of them never hear about until they are already in treatment is the one their care team spends the most time preparing them for — because getting the timing of that first injection wrong is what causes problems, not the medication itself.

Why the First Injection Isn’t Just Another Appointment

Vivitrol is an opioid antagonist. It doesn’t suppress cravings the way an agonist medication does — it physically occupies opioid receptors so opioids can’t bind to them. That mechanism is exactly why the appointment has to be scheduled carefully rather than started the day someone walks in the door.

Precipitated withdrawal: if naltrexone is injected while opioids are still active in a person’s system, it displaces them from the receptor all at once, which can trigger sudden, severe withdrawal within minutes rather than the gradual course withdrawal normally follows.

Receptor blockade: once the injection is given, it binds opioid receptors for roughly four weeks, which is what makes it useful for relapse prevention but also why the pre-injection window matters — there’s no undoing an injection once it’s administered.

Loss of tolerance: because the medication works by blocking opioids rather than replacing them, a person’s tolerance can drop during treatment, which is part of why the care team also spends time on overdose risk if a dose is ever missed or treatment is stopped.

Why You Have to Be Opioid-Free First

Every program that offers Vivitrol builds in an opioid-free period before the first dose, confirmed by a urine drug screen rather than by self-report. The exact number of days depends on what someone was using: shorter-acting opioids generally clear the body faster than longer-acting ones like methadone, which is why a physician sets the window individually instead of applying one fixed number to everyone. This is one of the main reasons medically supervised detox comes before induction rather than happening at the same time — the detox team is also the team tracking how many opioid-free days have passed.

What Actually Happens at the Appointment

The appointment itself is short. A nurse or physician confirms the urine screen is clean, reviews current medications and liver function labs (naltrexone is processed by the liver, so this gets checked before every course of treatment), and gives the injection intramuscularly, usually in the gluteal muscle. Most people feel soreness at the injection site for a day or two; that’s the most commonly reported side effect. The visit is scheduled, not spontaneous — it’s built into a discharge or step-down plan well before the injection date arrives.

Before that appointment, it’s worth asking your care team three specific questions: how many opioid-free days they’re requiring based on what you were using, whether the injection will happen before or after you leave residential care, and who administers and tracks your next dose once you’re no longer on-site. Getting clear answers to those three questions before the appointment, not during it, is what keeps a four-week medication schedule from quietly lapsing after discharge.

How This Fits Into Planning at a Six-Bed Residence

At a small residential program — Annandale operates a six-bed house rather than a large campus — medication timing has to be coordinated individually rather than run on a fixed clinic schedule, since there usually isn’t another client on the same induction timeline in the house at the same time. That means the physician who orders the injection, the nurse who confirms the drug screen, and the discharge planner who books the follow-up dose are often coordinating around one person’s calendar rather than a weekly injection clinic. For opioid use disorder that’s also being treated alongside a co-occurring condition — depression, anxiety, or PTSD are common examples — that same small-caseload coordination is part of how dual diagnosis care stays connected instead of being handled by two separate providers who never talk to each other.

Why the Monthly Shot Instead of a Daily Pill

Naltrexone also comes as a daily oral tablet, and some alcohol use disorder programs still use that form. For opioid use disorder specifically, most programs favor the extended-release injectable over the pill for one practical reason: adherence. A daily pill depends on someone remembering to take it every single day, indefinitely, often during the exact period — the first weeks after leaving residential care — when routines are least stable and relapse risk is highest. One injection removes that daily decision for about four weeks at a stretch. It doesn’t make the medication more effective on a per-dose basis; it just removes the most common way medication plans quietly fall apart.

Before the Appointment: Insurance and Timing

Extended-release naltrexone is a specialty medication, and most insurance plans, including PPO plans, require prior authorization before it will be covered — a step that can take several business days and needs to be started before the opioid-free window is even complete, not after. A discharge planner or case manager typically starts that authorization as soon as detox begins, precisely so the appointment isn’t held up waiting on a fax from an insurance company after someone has already cleared the clinical requirement. Anyone with questions about how their specific plan covers this medication can ask our admissions team directly at (855) 778-8668.

If a Dose Gets Missed

The receptor blockade fades gradually over the fourth week, which means tolerance can be lower than it was before treatment by the time a dose is due. If a scheduled injection is missed and opioid use resumes, that drop in tolerance is exactly what raises overdose risk — a dose that felt manageable before treatment can be dangerous afterward. This is why programs build in a call or check-in around the four-week mark rather than leaving the next appointment entirely up to the person to remember, and why any gap in the schedule should be reported to the prescribing physician right away rather than restarted informally.

What Vivitrol Doesn’t Do

Naltrexone treats opioid use disorder; it is not a treatment for depression, anxiety, or any other mental health condition on its own, and no one should expect it to resolve a co-occurring diagnosis by itself. It also doesn’t replace residential treatment or counseling — it’s one part of a plan that includes both. And because tolerance can drop while someone is protected by the receptor blockade, missing a scheduled dose or stopping the medication without medical guidance raises real overdose risk if opioid use resumes; any change to the schedule should go through the prescribing physician, not be decided alone.

This article is educational and isn’t a substitute for a medical evaluation. If you or someone you know is in a mental health crisis or having thoughts of suicide, call or text 988 to reach the Suicide & Crisis Lifeline, available 24/7. To ask about opioid use disorder treatment, medication options, or admission at Annandale Behavioral Health, call (855) 778-8668.

Sources: National Institute on Drug Abuse; Substance Abuse and Mental Health Services Administration. Call (855) 778-8668 to speak with our admissions team about opioid use disorder treatment.