Rat experiments could see new pain relieving injections

Pain relieving injections for osteoarthritis sufferers (OA) which avoid the risk of hyperthermia and potentially eliminate the need for surgery, have been discovered in experiments using rats.

At the moment people experiencing the severe pain associated with OA are offered pain relieving drugs such as steroid injections and anti-inflammatory drugs, which reduce inflammation.
Severe side effects, however, limit their use.

Previous clinical trials to block pain receptor TRPV1 failed as they had adverse effects on body temperature, resulting in hyperthermia.

Now researchers from The University of Nottingham have experimented with 176 rats to see whether this side effect can be avoided by an injection directly to the joint.

Dr Sara Kelly, a lecturer in neuroscience at the university, and one of the lead researchers on the project, said: “Using a model of human osteoarthritis pain we wanted to investigate if by blocking these receptors locally within the diseased joint, could we reduce the pain caused by osteoarthritis, without the side effect of hyperthermia — and the answer is yes.
 
“Osteoarthritis is a very common disease and the pain it causes is severe and can last a life time.

"A lot of patients who suffer with osteoarthritis are elderly and it would be better if we could treat their pain by giving them a drug, rather than putting them through a major surgical procedure like a joint replacement.

"The annual cost of joint replacement to the NHS is close to £200 million, which is another reason to look for a more effective solution.
 
“By targeting the joint directly, we did not see the side effect of hyperthermia, which is thought to be generated outside of the joint at the level of abdominal organs."

Clinical trials in human patients will now need to be undertaken.

In this country alone, osteoarthritis affects more than eight million people. An ageing population and growing obesity epidemic will see this figure rise.
 
Prof Alan Silman, medical director of Arthritis Research UK, which funded the research, said: “We desperately need new approaches to treating the pain of osteoarthritis.

"For some years this particular pathway has shown potential as a means by which osteoarthritic pain may be transmitted, but until now attempts at blocking this pathway have caused unacceptable side-effects.
 
“This research seems to suggest it might be possible to overcome this and to provide a novel and effective approach to targeting osteoarthritis.”

To view the full research paper — Increased Function of Pronociceptive TRPV1 at the Level of the Joint in a Rat Model of Osteoarthritis Pain — click here.