Codeine is used for mild to moderate pain relief. It is also used to reduce coughing, usually in combination with other drugs. Codeine will assist in alleviating symptoms but will not treat the cause or speed of recovery. Codeine is in the category of opiate (narcotic) analgesic medicines and in the category of medications called antitussives. When codeine is used to treat pain, the reaction of the brain and nervous system to pain changes.