Naltrexone 50 mg Tablets 100 Count (RX)Naltrexone 50 mg Tablets Naltrexone is a long acting opioid receptor antagonist (a pure opiate blocker) available as a 50 mg oral tablet (brand names: ReVia, Depade, generics) and as a 380 mg monthly gluteal injection (Vivitrol). It has high affinity for opioid receptors (and to a lesser degree receptors) but no agonist effects. In practice, naltrexone blocks the effects of opioids (preventing their euphoria and analgesia) and dampens alcohols