Final answer:
Naltrexone is the medication that is not used in the treatment of opioid maintenance and relapse prevention.
Step-by-step explanation:
The medication that is not used in the treatment of opioid maintenance and relapse prevention is Naltrexone. Naltrexone is a narcotic antagonist that is used to maintain individuals on chronic therapy with a narcotic antagonist. It works by blocking the effects of opioids and preventing their euphoric and analgesic effects. Therefore, it is not suitable for opioid maintenance and relapse prevention.