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Codeine is a type of medication belonging to a class of drugs known as opioid analgesics, which are derived from the Papaver somniferum, a type of poppy flower, or are manufactured to chemically resemble the products of that poppy. In Latin, Papaver refers to any flower of the poppy variety, while somniferum translates to mean "maker of sleep." The plant has been used for over 6,000 years, beginning with the ancient cultures of Egypt, Greece, Rome, and China, to cause sleep. Analgesics are drugs which provide relief from pain. Codeine, an opioid analgesic, decreases pain while causing the user to feel sleepy. At lower doses, codeine is also helpful for stopping a cough.

Although codeine is present in nature within the sticky substance latex which oozes out of the opium poppy's seed pod, it is present in only small concentrations (less than 0.5). However, morphine, another opioid analgesic, is present in greater concentrations (10) within the opium poppy's latex, and codeine can be made from morphine via a process known as methylation, which is the primary way that codeine is prepared.

Codeine is a centrally acting drug, meaning that it goes to specific areas of the central nervous system (in the brain and spinal cord) to interfere with the transmission of pain, and to change your perception of the pain. For example, if you have your wisdom teeth removed and your mouth is feeling very painful, codeine will not go to the hole in your gum where the tooth was pulled and which is now throbbing with pain, but rather will act with the central nervous system to change the way you are perceiving the pain. In fact, if you were given codeine after your tooth was pulled, you might explain its effect by saying that the pain was still there, but it just was not bothering you anymore.

Codeine's anti-tussive (cough stopping) effects are also due to its central actions on the brain. It is believed that codeine inhibits an area of the brain known as the medullary cough center.

Codeine is not as potent a drug as is morphine, so it tends to be used for only mild-to-moderate pain, while morphine is useful for more severe pain. An advantage to using codeine is that a significant degree of pain relief can be obtained with oral medication (taken by mouth), rather than by injection. Codeine is sometimes preferred over other opioid analgesics because it has a somewhat lower potential for addiction and abuse than do other drugs in that class.

Scientists are currently trying to learn more about how codeine and other opioid analgesics affect the brain. It is interesting to note that there are certain chemicals (endorphins, enkephalins, and dynorphins) which are made within the brains of mammals, including humans, and which closely resemble opioid analgesics. In fact, the mammalian brain itself actually produces tiny amounts of morphine and codeine! Some of these chemicals are produced in the human brain in response to certain behaviors, including exercise. Exploring how and when human brains produce these chemicals could help scientists understand more about ways to control pain with fewer side effects, as well as helping to increase the understanding of addictive substances and behaviors.

See also Narcotic.



Berkow, Robert, and Andrew J. Fletcher. The Merck Manual of Diagnosis and Therapy. Rahway, NJ: Merck Research Laboratories, 1992.

Katzung, Bertram G. Basic & Clinical Pharmacology. Norwalk, CT: Appleton & Lange, 1992.

Marieb, Elaine Nicpon. Human Anatomy & Physiology. 5th ed. San Francisco: Benjamin/Cummings, 2000.

Rosalyn Carson-DeWitt

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