Codeine may increase pain sensitivity

Large, frequent doses of codeine may increase sensitivity to pain without offering the same relief as morphine, according to a study from the University of Adelaide in Australia. And, the problem seems to be worst in people taking codeine for headaches.

Codeine, which is in a class of drug called opioids is commonly used to treat headaches. According to researchers, patients have been known to complain that their headaches worsen after regular usage of codeine.

For the study, researchers did a series of mouse experiments to see if codeine increases pain sensitivity and pain caused by non-injurious stimuli.  A group of male mice were randomized to undergo treatments over 4 days. Some mice underwent von Frey testing, which involves fine-gauge metal wires to test for pain sensitivity. Others underwent hot plate tests, and others had chronic constriction injury surgery.  All the mice were monitored for their response to codeine and morphine.

Researchers found that codeine provided significantly less pain relief compared to morphine, but both had the same level of increased pain sensitivity.They say people who take codeine every now and then have nothing to worry about, but it could be detrimental to those who take high doses regularly for chronic pain or headache.

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Sourced from: Medical News Today, Codeine linked to increased pain sensitivity