Codeine is opium that is used during the treatment of restlessness, cough, and diarrhea. And it is similar to morphine and hydrocarbons as an alcoholic anxiety-reliever and phlegm suppressant. Additionally, codeine converts a small amount of codeine into morphine throughout the body. The exact active ingredient is not recognized; However, codeine, like morphine, connects to nerves in the brain that are necessary to express the feeling of pain in the body and brain.