Which medication blocks the effects of opiates at receptor sites and is used to prevent relapse?

• A. Naltrexone
• B. Methadone
• C. Buprenorphine
• D. Disulfiram

Answer: (A)

Blocking opioid effects at receptor sites with an antagonist helps prevent relapse by removing the rewarding effects of opioids. Naltrexone binds tightly to mu-opioid receptors in the brain without producing opioid effects of its own, so opioids can’t activate those receptors and the usual high is blocked. Because it blocks the reinforcing experience, it supports abstinence after detoxification and is used specifically to prevent relapse. It can be taken as a daily pill or given as a long-acting injectable. This differs from methadone or buprenorphine, which are opioid receptor activators (a full agonist and a partial agonist, respectively) used to manage withdrawal and cravings by stimulating the receptors. Disulfiram, on the other hand, is used to deter alcohol use and has no role in blocking opioid receptors.