Opioid use disorder (OUD) remains a complex and escalating public health crisis, particularly in North America, driven by both historical overprescribing and the widespread availability of synthetic opioids such as fentanyl. This thesis critically examines the pharmacological management of OUD, focusing on the mechanisms, pharmacokinetics, and clinical application of methadone, buprenorphine, and naltrexone. Comparative analysis highlights important differences in safety, treatment retention, and accessibility, emphasizing the clinical advantages of opioid agonist therapies. Emerging therapies are also explored, though current evidence supports their role primarily as adjunctive options. Overall, this work underscores the importance of individualized treatment strategies and the integration of harm reduction approaches in improving patient outcomes.