Naltrexone Hydrochloride API Powder Bulk For Custom Compounding (Rx)Naltrexone Hydrochloride (API Powder) Naltrexone hydrochloride is a pure opioid receptor antagonist used in addiction treatment. It is a synthetic relative of the opioid drug oxymorphone, but unlike opioids it has no agonist (euphoric) activity. In other words, naltrexone binds tightly to opioid receptors (especially the mu receptor) and blocks (antagonizes) them, preventing opioids (like heroin, morphine or oxycodone) from producing their effects. By