Commit to Opioid Medical Prescriber Accountability and Safety for Seniors Act of 2018 This bill requires the Centers for Medicare & Medicaid Services (CMS) to identify outlier prescribers of opioids under the Medicare prescription drug benefit and Medicare Advantage prescription drug plans. Specifically, the CMS must: (1) establish an opioid-prescription threshold for determining whether a prescriber is an outlier compared to other prescribers, based on specialty and geographic area; (2) use National Provider Identifiers (unique provider identification numbers currently included on claims for covered drugs) to identify outlier prescribers; and (3) annually notify identified outlier prescribers of their status and provide them with resources on proper prescribing methods. The CMS may also identify and notify outlier prescribers based on co-prescriptions of covered drugs that have adverse effects when used in combination with opioids. Persistent outlier prescribers are subject to additional requirements.