What side effects are most common with Vivitrol (naltrexone)
Vivitrol (extended-release naltrexone) can cause side effects related to both the medication itself and the injection site. Commonly reported effects include nausea and headache. Injection-site reactions are also frequent, such as pain, redness, swelling, and induration where the shot was given.
What injection-site reactions should you watch for
Because Vivitrol is given as a deep intramuscular injection, local reactions are a key concern. Patients may experience soreness or pain at the injection site, along with redness, swelling, or a firm area under the skin. In most cases these reactions resolve, but symptoms that worsen, spread, or persist should be assessed by a clinician.
What serious side effects are possible
Serious adverse events are less common, but they can occur. Seek urgent medical care if you develop signs of a severe allergic reaction (such as trouble breathing, facial or throat swelling), or other concerning symptoms that you did not have before starting treatment. Liver-related problems are also a safety consideration for naltrexone-class medications, so new or worsening symptoms like unusual fatigue, dark urine, or yellowing of the skin/eyes should prompt prompt evaluation.
Can Vivitrol cause withdrawal-like symptoms?
Vivitrol blocks opioid receptors. If a person has opioids in their system (or has recently used opioids), starting naltrexone can precipitate withdrawal symptoms. Symptoms can include agitation, body aches, nausea/vomiting, sweating, diarrhea, and abdominal cramps. This is one reason clinicians screen for opioid use before beginning treatment.
What side effects matter most for alcohol use disorder vs opioid use disorder
Vivitrol is used for both alcohol use disorder (to help prevent relapse) and for preventing relapse after opioid detoxification. Side effects can look similar across uses (including injection-site reactions), but opioid-related safety issues, like precipitated withdrawal if opioids are still present, are particularly relevant for patients transitioning from opioid treatment.
What patients ask about: interactions and “why can’t I take pain meds?”
A major practical effect of Vivitrol is that it blocks opioid pain medicines and other opioids. If you need pain control or have used opioids recently, talk to your prescriber before taking additional medications. Trying to overcome the blockade with opioids can be dangerous and is not advised.
When to contact a doctor right away
Contact a healthcare professional promptly for worsening injection-site symptoms, signs of liver problems (fatigue, dark urine, jaundice), or possible allergic reaction symptoms (trouble breathing, facial/throat swelling). Get emergency care for severe reactions.
Sources
No sources were provided in your prompt, so I cannot cite specific prescribing-label details for Vivitrol here. If you want, share the label text you have (or tell me which country’s label you’re using), and I can restate the side effects exactly as listed there.