Codeine is an alkaloid obtained from opium or prepared from morphine by methylation.
It is used as a narcotic analgesic for mild to moderate pain, and as an antitussive. The phosphate and sulphate salts are soluble in water. It can be administered intravenously, intramuscularly or orally.
It is useful after head injury because it causes less respiratory depression than the other opiates.
This drug may cause constipation. It should not be used in those less than one year old.