Codeine is an alkaloid found in opium in concentrations ranging from 0.7 to 2.5 percent. Most codeine used in the United States is produced from morphine. This is interesting since the pharmacological effects experienced after codeine administration are due to morphine. The liver converts codeine to morphine. In a few people, however, the enzyme responsible for this metabolism is missing and thus codeine is virtually ineffective in these individuals. Compared to morphine, codeine produces less analgesia, sedation, and respiratory depression, and is frequently taken orally.
Codeine is medically prescribed for the relief of moderate pain. It is made into tablets either alone or in combination with aspirin, acetaminophen (Tylenol®) or ibuprophen. Codeine is an effective cough suppressant and is found in a number of liquid preparations. Codeine products are also used to a lesser extent as an injectable solution for the treatment of pain. It is by far the most widely used naturally occurring narcotic in medical treatment in the world. Codeine products are encountered on the illicit market, frequently in combination with glutethimide (Doriden®) or carisoprodol (Soma®).
See also dihydrocodeine.