Naltima (naltrexone) works by blocking the addictive effects of narcotics, including alcohol, especially the effects of “high” feeling that you get after using them. The drug also blocks the euphoric feeling that may get after drinking alcohol. The drug does not produce narcotic-like effects or cause any mental dependence. Naltima will not prevent your desire to drink alcohol or curb your cravings to use opiates or opioid painkillers. Naltrexone is an opioid antagonist, meaning it suppresses the effects of opioids by acting on the central nervous system.