Codeine - Adverse Effects

Adverse Effects

Common adverse effects associated with the use of codeine include drowsiness and constipation. Less common are euphoria, itching, nausea, vomiting, dry mouth, miosis, orthostatic hypotension, urinary retention, depression, and pardoxical coughing. Rare adverse effects include anaphylaxis, seizure, 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 the 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 of 2012, the Federal Drug Administration issued a warning about deaths in pediatric patients < 6 years old after ingesting "normal" doses of acetaminophen with codeine after tonsillectomy. (http://www.fda.gov/Drugs/DrugSafety/ucm313631.htm#professionals). Some patients are very effective converters of codeine to its active form, hydromorphone, 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.