Codeine
From The Art and Popular Culture Encyclopedia
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Codeine or 3-methylmorphine (a natural isomer of methylated morphine) is an opiate used for its analgesic, antitussive, antidiarrheal, antihypertensive, antianxiety, sedative and hypnotic properties, to suppress premature labor contractions, myocardial infarction, suppress coughing, as well as many other uses. Codeine is the second-most predominant alkaloid in opium, at up to three percent. Although codeine can be extracted from natural sources, a semi-synthetic process is the primary source of codeine for pharmaceutical use. It is considered the prototype of the weak to midrange opioids (tramadol, dextropropoxyphene, dihydrocodeine, hydrocodone, oxycodone).
Adverse effects
Common adverse effects associated with the use of codeine include drowsiness and constipation. Less common are itching, nausea, vomiting, dry mouth, miosis, orthostatic hypotension, urinary retention, euphoria, dysphoria, and coughing. Rare adverse effects include anaphylaxis, seizure, acute pancreatitis and respiratory depression. As with all opiates, longer-term effects can vary but can include diminished libido, apathy and memory loss. Some people may also have an allergic reaction to codeine, such as the swelling of skin and rashes.
Codeine and morphine as well as opium were used for control of diabetes until relatively recently, and still are in rare cases in some countries, and the hypoglycemic effect of codeine, although usually weaker than that of morphine, diamorphine, or hydromorphone, can lead to cravings for sugar.
Tolerance to many of the effects of codeine develops with prolonged use, including therapeutic effects. The rate at which this occurs develops at different rates for different effects, with tolerance to the constipation-inducing effects developing particularly slowly for instance.
A potentially serious adverse drug reaction, as with other opioids, is respiratory depression. This depression is dose-related and is a mechanism for the potentially fatal consequences of overdose. As codeine is metabolized to morphine, morphine can be passed through breast milk in potentially lethal amounts, fatally depressing the respiration of a breastfed baby.
In August 2012, the Federal Drug Administration issued a warning about deaths in pediatric patients < 6 years old after ingesting "normal" doses of paracetamol with codeine after tonsillectomy.
Some patients are very effective converters of codeine to its active form, morphine, resulting in lethal blood levels. The FDA presently is recommending very cautious use of Codeine in young tonsillectomy patients: use the drug in the lowest amount that can control the pain, use "as needed" and not "around the clock", and seek immediate medical attention if a child on codeine exhibits excessive sedation or abnormally noisy breathing.
Withdrawal and dependence
As with other opiate-based pain killers, chronic use of codeine can cause physical dependence. When physical dependence has developed, withdrawal symptoms may occur if a person suddenly stops the medication. Withdrawal symptoms include: drug craving, runny nose, yawning, sweating, insomnia, weakness, stomach cramps, nausea, vomiting, diarrhea, muscle spasms, chills, irritability, and pain. To minimize withdrawal symptoms, long-term users should gradually reduce their codeine medication under the supervision of a healthcare professional.
Codeine is metabolized to codeine-6-glucuronide (C6G) by uridine diphosphate glucuronosyl transferase UGT2B7, and, since only about 5% of codeine is metabolized by cytochrome P450 CYP2D6, the current evidence is that C6G is the primary active compound. Claims about the supposed "ceiling effect" of codeine doses are based on the assumption that high doses of codeine saturate CYP2D6, preventing further conversion of codeine to morphine, however it is now known that C6G is the main metabolite responsible for codeine's analgesia.
