Chronic codeine – More pain than gain? the first evidence of codeine induced hyperalgesia.
J Johnson, M Hutchinson, D Williams, P Rolan
What is the problem you are trying to solve?
The widely used painkiller codeine is partially converted in the body to morphine, thus in this study we wanted to find out if codeine use over time can lead to increased sensitivity to pain, which is the case with morphine.
What is the hypothesis this study tested?
Codeine will increase sensitivity to stimuli which are usually painful (hyperalgesia) and stimuli which are not normally painful (allodynia), but it will do so to a lesser degree than morphine.
What was the conclusion?
Codeine is able to induce hyperalgesia to the same degree as morphine when given in equimolar doses, suggesting the increase in pain sensitivity observed is not solely dependent on the metabolism of codeine to morphine.
What is the clinical relevance of the work?
Codeine causes the same increase in pain as morphine but produces less pain relief at the same molar doses – perhaps we should use less codeine!