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It's E. Buprenorphine is a full agonist at opioid receptors.

Explanation: Clinicians have two general treatment paths: opioid maintenance treatment or detoxification. Agonist and partial agonist medications are commonly used for both maintenance and detoxification purposes; alpha2-adrenergic agonists are primarily used for detoxification. Antagonists are used to accelerate detoxification and then continued after detoxification to prevent relapse.

The principles of detoxification are the same for all drugs: to substitute a longer-acting, orally active, pharmacologically equivalent drug for the abused drug, stabilize the patient on the substituted drug, and then gradually withdraw it. Methadone is admirably suited for such use in opioid-dependent persons. Clonidine, a centrally acting sympatholytic agent, has also been used for detoxification. Clonidine has no narcotic action and is not addictive.

Because it is a partial agonist, buprenorphine produces fewer withdrawal symptoms and may allow briefer detoxifications compared with full agonists like methadone, but it does not appear to have better outcomes than methadone tapering. Buprenorphine is superior to the alpha2-adrenergic agonist clonidine in reducing symptoms of withdrawal, in retaining patients in a withdrawal protocol, and in treatment completion.

In October 2002, the Food and Drug Administration approved sublingual buprenorphine as a Schedule III drug for managing opiate dependence. Unlike the full agonist methadone, buprenorphine is a partial agonist of mu-opioid receptors with a slow onset and long duration of action, allowing for alternate-day dosing.

Naltrexone, a long-acting orally active pure opioid antagonist, can be given three times a week at doses of 100-150 mg, and a depot form for monthly administration is available. Because it is an antagonist, the patient must first be detoxified from opioid dependence before starting to take naltrexone.

Muskin PR and Dickerman AL, eds. Study Guide to Psychiatry: A Companion to the American Psychiatric Publishing Textbook of Psychiatry, Sixth Edition. Arlington, VA: American Psychiatric Association Publishing; 2015: 84, 351-352. Click here to purchase. Members can purchase at a discount.