Capsaicin, the component of chilli peppers that causes a burning sensation on the skin, has long been available for pain relief. However, its side effects limit its use.
Now a synthetic, modified version of capsaicin known as capsazepine has been found to desensitive pain receptors in a similar way without the side effects. (Large doses of capsaicin can dangerously increase body temperature, leading to a loss of blood supply to vital organs.)
In a study published in Scientific Reports, mice were given a high but tolerable dose of capsazepine over the course of several days.
The dose was found to desensitise a pain receptor called TRPA1, also known as the mustard oil receptor because it is activated by a substance found in mustard, horseradish and onions.
Researchers say that capsazepine could be used as a painkiller for diseases in which the mustard oil receptor plays a key role, including chronic inflammatory bowel disease, joint arthrosis, chronic pancreatitis, Crohn’s disease and chronic asthma.
Guidelines and advice on commonly used painkillers in the UK are constantly changing, and it is getting more difficult for doctors to find safe and effective pain relief for patients without running the risk of potentially serious risks being incurred at the same time.
New developments in this area are few and far between, so this study is a potential cause for optimism for the development of the next generation of painkillers. Topical capsaicin — derived from chillies — has long been available for pain relief but many users report unacceptable levels of burning to the skin when applied and so have to stop using it.
This research has looked at a similar substance — capsazepine — that appears to desensitise the nerve cells that transmit pain signals in the body without the potential side effects of capsaicin.
Although this is an animal study, if these findings are reproduced next in human trials it raises the possibility of a new way of treating the pain of many conditions such as arthritis, pancreatitis and inflammatory bowel disease that are currently often hard to treat. However, as with so many such studies, not only do large-scale trials on humans now have to occur, but the initial findings have to be consistently reproduced. Nothing is going to happen quickly here, and the current arms’ chest of painkillers available to doctors remains the same.
Research score: 3/5