Final answer:
Naltrexone is the drug used to maintain abstinence in heroin addicts and to reduce cravings for alcohol and nicotine. It acts as a narcotic antagonist, blocking the euphoric effects of opioids, and is also useful in treating alcohol dependence.
Step-by-step explanation:
This medication was made clinically available in 1985 as a narcotic antagonist, which means it counters the effects of opioids on the brain. Unlike methadone, which is a synthetic opioid used to help manage opioid withdrawal symptoms, naltrexone works by blocking the euphoric and sedative effects of drugs like heroin. When taken by individuals in recovery, it makes the use of opioids less rewarding, thereby supporting abstinence. Naltrexone can also help reduce cravings for alcohol and has been used for alcohol dependence treatment. It is administered orally and requires only a daily dose due to its long-lasting effects.