OPRM1 and Euphoria: Opioid addiction is mediated by the μ-opioid receptor (mOR), which binds substances like heroin and fentanyl, producing analgesia and euphoria.26 FDA-approved treatments such as methadone (a full mOR agonist) and buprenorphine (a partial agonist) mitigate withdrawal symptoms and cravings, while naltrexone, an opioid receptor antagonist, blocks the effects of opioids and prevents relapse.27 In addition, the κ-opioid receptor (KOR) is a target,28 as its modulation may reduce stress-induced relapse, offering a potential avenue for future drug development.