Which medication is not commonly used in the treatment of opioid abuse?

Luminal, which is the brand name for phenobarbital, is not commonly used in the treatment of opioid abuse. This medication is primarily a barbiturate used to treat seizure disorders and as a sedative. In the context of opioid abuse treatment, medications like buprenorphine and methadone are specifically designed to manage opioid dependency. They work by partially stimulating opioid receptors in the brain to reduce cravings and withdrawal symptoms, providing a safer avenue for individuals in recovery. Oxycodone, on the other hand, is an opioid pain medication and is not used in treatment due to its potential for abuse and dependence. Therefore, while buprenorphine and methadone are integral components of opioid substitution therapy, Luminal does not have a role in this specific treatment paradigm, making it the correct choice for this question.