Intramuscular, extended-release naltrexone inadvertently administered in the deltoid muscle: A case report

Extended-release, intramuscular (IM) naltrexone can be an effective and convenient medication option for alcohol use disorder. We sought to assess the clinical impact of an alternate, if inadvertent, administration of IM naltrexone in the deltoid muscle instead of the recommended gluteal muscle.

IM naltrexone was prescribed to a hospitalized 28-year-old man with severe alcohol use disorder as part of an inpatient clinical trial. A nurse unfamiliar with naltrexone administration mistakenly administered the drug to the deltoid instead of the gluteal muscle recommended by the manufacturer. Despite concerns that injection of the large-volume suspension to the smaller muscle would potentially contribute to increased pain and higher chance of adverse events owing to faster medication absorption, the patient experienced only mild discomfort to the deltoid region, without other adverse events on immediate physical and laboratory examinations. The patient later denied additional adverse events in the period after hospitalization, but he did not endorse any anti-craving effect of the medication, resuming drinking alcohol quickly following initial discharge.

This case represents a unique procedural challenge of administering a medication in the inpatient setting that is typically given in the outpatient setting. Inpatient staff members frequently rotate and may be relatively unfamiliar with IM naltrexone, so handling should be limited to personnel who have received focused training on its administration. Fortunately, in this case deltoid administration of naltrexone was well-tolerated and even deemed quite "acceptable" to the patient. Clinically, the medication was insufficiently effective, but biopsychosocial context may have made his AUD especially refractory. More research is needed to fully establish whether naltrexone given via deltoid muscle injection has comparable safety and efficacy to gluteal muscle administration.