Codeine works in the body because roughly 10% of it is transformed into morphine, which is what relieves the pain. In reality, codeine is a prodrug, which means that the body's metabolism transforms it into the active drug molecule. The mu opioid receptors in the central nervous system are where morphine binds. It's unclear how oxycodone functions. Codeine is considered an opioid because it interacts with and activates the opioid receptors in the brain, which are essential for pain transmission. In half an hour, the medicine is metabolized by the liver and starts to have an effect by changing how the brain and nervous system react to pain all over the body, increasing general tolerance, and lessening the pain, aches, and soreness.