Codeine Tablets for Relive Pain in Minutes Codeine is an Opioid pain drug, which effectively treats mild to moderate pain. It is a combination of narcotic and analgesic/antipyretic, which works in the brain and nervous system to decrease pain. Codeine tablets work well for men and women to cure pain or pain-related sleep problems. They work by blocking the pain signals sent to the brain by the nerves and produce a calming effect, which in turns causes relaxation and sleep at night.