Morphine is an opioid pain medication. An opioid is sometimes called a narcotic. Naltrexone is a special narcotic drug that blocks the effects of other narcotic medicines and alcohol. Morphine and naltrexone is a combination medicine used to treat moderate to severe pain when around-the-clock pain relief is needed for a long time period. Morphine and naltrexone is an extended-release opioid pain medicine that is not for use on an as-needed basis for pain. Morphine and naltrexone may also be used for purposes not listed in this medication guide.