MOA: mu opioid receptor antagonist which prevents exogenous opioids from binding blocking the pleasurable effects of opioid use. Reduces alcohol consumption through modulation of the opioid system, blocking the reinforcing effects of alcohol. 

FDA Indications: alcohol use disorder (oral or injectable), Prevention of relapse to opioid dependence (injection)

Oral Dose: 50 mg/day 

Injection Dose: 380 mg/month 

Caution: patient must be opioid free for 7-10 days prior to starting, conformed with a negative urine 

For alcohol use disorder start with 50 mg/day or 380 mg/month for IM formulation (injection may be preferred because it eliminates the daily decision to take the medication) 

Side effects: nausea, vomiting, decreased appetite, dizziness, injection site reaction, life-threatening side effect is hepatocellular injury in overdose 

Who is it good for?: Those ready to abstain completely from alcohol and for binge drinkers. Good evidence for reducing heavy drinking days. There is some risk of apathy or loss of pleasure with chronic use. The combination of naltrexone and bupropion has been used as a treatment for obesity.