The nurse managing SUD implements withdrawal protocols, coordinates MAT initiation, manages comorbid medical complications, and facilitates transition to ongoing recovery services. Alcohol withdrawal pathophysiology involves chronic GABA-A receptor downregulation and glutamate NMDA receptor upregulation from prolonged alcohol exposure. When alcohol is removed, the inhibitory GABA system is insufficient and the excitatory glutamate system is overactive, producing CNS hyperexcitability manifesting as tremor, seizures, and delirium. CIWA-Ar protocol implementation: assess every 1-2 hours; score 0-9 (mild, supportive care), 10-18 (moderate, pharmacological treatment indicated), above 18 (severe, intensive monitoring). Benzodiazepine selection: long-acting (chlordiazepoxide, diazepam) for uncomplicated withdrawal; lorazepam for hepatic impairment (conjugation metabolism, not oxidation). Refractory DTs may require phenobarbital or propofol/ICU transfer. Opioid MAT initiation requires understanding of pharmacology: buprenorphine (partial agonist, ceiling effect, precipitated withdrawal risk if given too early, safe in overdose); methadone (full agonist, no ceiling effect, overdose risk, QTc prolongation, requires federally licensed opioid treatment program); naltrexone (full antagonist, blocks opioid effects, requires 7-10 days opioid-free before starting, available as monthly injection).