A compound extracted from the legs of centipedes could one day become a potent pain reliever, new research in mice suggests.
"The molecule we discovered was at least as good as, and sometimes significantly better than morphine," said study co-author Glenn King, a biochemist at the University of Queensland in Australia.
And unlike morphine or other painkillers, the centipede venom compound didn't seem to have side effects on the mice, or tend to create tolerance or addiction, King said.
With each nasty sting, centipedes produce just a few microliters of venom, which they release from their front pair of legs. Most people who've been bitten say it is excruciatingly painful.
But many venoms have intriguing physiological effects, so King and his colleagues have spent hours milking the venom of Chinese red-headed centipedes, and analyzing the hundreds of compounds in the substance to look for promising drug candidates.
"They're nasty little buggers to try to milk because they're so wiggly," King told LiveScience. "If you don't hold them down right, they can just turn around and bite you."
One of the compounds in the venom seemed to block a specific sodium channel in cells, the researchers found. Centipedes likely evolved this venom molecule to kill insects, but in humans, this channel works by translating painful sensations to a feeling of pain in the brain. [10 Things You Didn't Know About the Brain]
Some people are born with genetic mutations that render the channel nonfunctional. Those with this mutation feel no pain and can't smell anything, but are otherwise perfectly healthy.
To test the compound, the team gave it to mice, then subjected the animals to pain from several sources, such as acid and heat. Mice given the compound experienced much less pain than control mice, and the drug's pain relief was equivalent to that of opioids, the researchers found.
In addition, the team detected no side effects. Because people who lack this channel are healthy, the researchers said they expect that side effects of the compound in humans should also be minimal.
The findings suggest the new compound could be useful for treating chronic pain and other types of recalcitrant pain, King said.
Opioids, the current first-line options for many types of pain, often don't work for people with certain types of pain, and cells stop responding to the drugs over time. That requires people to take larger and larger doses to get the same effects. In addition, opioids plug into the body's natural reward system, which creates a high and makes the medicines potentially addictive.
By contrast, this newly discovered molecule doesn't tap into the body's feel-good system, circumventing the potential for addiction. The researchers said they also suspect that the compound will not produce the same tolerance effects over time.
Still, studies in humans are needed to determine if the compound works in people, and if it is safe. The team is also studying several other venom compounds that block the same channel, so it may be that another compound proves more effective in the long run, King said.
The finding was detailed Sept. 30 in the journal Proceedings of the National Academy of Sciences.