Codeine, a second-most predominant alkaloid in opium, is both a medical and legal narcotic known for its pain-relieving and cough-suppressing properties, but it is also highly addictive. As a Schedule II drug, pure codeine has a high potential for abuse, although certain formulations like cough syrups are classified differently due to their lower abuse risk. The document discusses its medical uses, history, legal classification, and the pros and cons of its use.