Final answer:
Naltrexone is most effective in preventing relapse of opioid dependency in individuals who have more to gain by being drug-free rather than drug dependent.
Step-by-step explanation:
Naltrexone is most effective in preventing relapse of opioid dependency in individuals who have more to gain by being drug-free rather than drug dependent. This includes individuals who are motivated to recover from addiction and live a drug-free life. Naltrexone works by blocking the effects of opioids, so when someone on naltrexone takes an opiate, it will have little to no effect.