Naltrexone is a non-narcotic drug that has been in use for alcohol withdrawal since 1994. As an opioid antagonist, naltrexone blocks the pleasurable effects of alcohol in the reward center of the brain. As a result, the desire or temptation to use the substance is greatly diminished, allowing recovery to progress. Naltrexone is available in a daily pill form, as a monthly time-release injection, or as a pellet implant that can last for months.