Opioid receptor antagonist Works by blunting feeling of intoxication and lead to less craving. Lowers risk to return drinking 4% Dose 50 mg/d Cost $3/pill. Can start while drinking. Vivitrol injectable 380 mg IM monthly SE: Nausea, dizziness. Serious SE: liver toxicity Monitor baseline LFT and Q 3 mo. Contraindicated if currently on opioids, or liver failure.