Using large and frequent doses of the pain-killer codeine may actually produce heightened sensitivity to pain, without the same level of relief offered by morphine, according to new research from the University of Adelaide.
Researchers in the Discipline of Pharmacology have conducted what is believed to be the world's first experimental study comparing the pain relieving and pain worsening effects of both codeine and morphine.
The University's Professor Paul Rolan, who is also a headache specialist at the Royal Adelaide Hospital, says codeine has been widely used as pain relief for more than 100 years but its effectiveness has not been tested in this way before.
"In the clinical setting, patients have complained that their headaches became worse after using regular codeine, not better," Professor Rolan says.
"Codeine use is not controlled in the same way as morphine, and as it is the most widely used strong pain reliever medication in the world, we thought it was about time we looked into how effective it really is."