Common adverse effects of oral naltrexone (vs. placebo) include somnolence (29.5% vs. 17.8%), nausea (25.8% vs. 16.3%), vomiting (16.9% vs. 10.4%), decreased appetite (17.7% vs. 11.8%), abdominal pain (15.9% vs. 7.5%), insomnia (16.4% vs. 13.4%), and dizziness (11.9% vs. 6.2%).14 The drug blocks the therapeutic effects of opioid analgesics and can precipitate opioid withdrawal in a patient who is physically dependent on opioids. Long-acting naltrexone can cause the same adverse events as oral naltrexone and also injection site reactions.19
