https://nuheals.com/pain-relief/codeine-30-mg/ Codeine 30 mg is a prescription opioid medication often used to manage mild to moderate pain. When taken, it typically works by binding to opioid receptors in the brain and spinal cord, altering the way your body perceives and responds to pain. Codeine 30 mg can help calm pain fairly quickly, usually within 30 to 60 minutes of taking it.