Hydrocodone is a pain reliever that reduces pain in the body. It's also used to treat cough, diarrhea and symptoms of withdrawal in people who are addicted to opioids. Hydrocodone may also be used for other purposes not listed in this medication guide. Hydrocodone is an opioid medication that's used to treat pain. Take it with a full glass of water, with or without food. Do not take more than directed.