Inclusion Criteria:  Participants will include hospitalized adults, aged 18 to 65 years old, who receive care from the ACS during their hospitalization and who meet DSM - 5 criteria for alcohol use disorder.  Exclusion Criteria:  Naltrexone is contraindicated in acute hepatitis or liver failure and its use in patients with active liver disease must be carefully considered in light of the potential for hepatotoxic effects.23 It is also contraindicated in patients taking opioids for pain due to its antagonism at the opioid receptor.23 The investigators will exclude people who meet the following criteria:  Liver function test (AST/ALT) more than five times the upper limit of normal Decompensated liver failure defined as use of lactulose for prevention of hepatic encephalopathy, ascites, use of spironolactone and/or lasix for ascites, presence of hepatic encephalopathy, International Normalized Ratio (INR) >2, or thrombocytopenia in the setting of known liver disease Renal failure, defined as a glomerular filtration rate of <30 ml/min On opioids for acute or chronic pain at time of study enrollment Pregnancy, IM naltrexone is not FDA approved in pregnancy