Vivitrol (injectable naltrexone) has its own specific side effect profile worth understanding, including a liver-related warning that shapes how treatment is monitored.
Common side effects:
- Injection site reactions — pain, swelling, or in rare cases, more serious skin reactions at the injection site
- Nausea, especially after the first injection
- Headache
- Fatigue
- Muscle cramps
The liver consideration: Naltrexone carries an FDA warning regarding liver function, particularly at higher oral doses — the injectable form (Vivitrol) is generally considered lower risk than high-dose oral naltrexone, but many prescribers still check liver function before starting and periodically during treatment, especially if you have any history of liver disease.
Injection site reactions specifically: Rare but serious reactions (significant swelling, tissue damage) have been reported — any injection site reaction that seems to be worsening rather than improving over the days after an injection warrants contacting your provider.
What’s routine monitoring vs. a red flag: Baseline and periodic liver function tests are standard practice, not a sign something is wrong. Yellowing of skin or eyes, unusual fatigue combined with abdominal pain, or dark urine would be reasons to contact your provider promptly rather than wait for a scheduled check.
Medically reviewed by [pending]. Source: FDA prescribing information for Vivitrol.