Codeine is a narcotic pain reliever, which is also effective in reducing certain types of coughing. It is included in many types of prescription cough syrups as an antitussive, or cough suppressant. Cough medicine with codeine generally is available only by prescription, although some states allow medications with small amounts to be sold over the counter.
Codeine is an effective temporary treatment for coughing due to bronchial and throat irritation.
Codeine is converted to morphine when it reaches the brain, where it is an effective pain reliever and also suppresses the brain's cough center.
Codeine can cause drowsiness, which allows a person to get some sleep after being kept awake by coughing. Sleep is an important component in healing.
Cough medicine with codeine only works effectively on non-productive coughing, as opposed to productive coughing, which results in mucous being coughed up.
Codeine also does not work for a persistent cough related to smoking, emphysema or asthma.