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Painkillers most effective on redheaded women


Redhead women have a gene that means they respond beter to painkillers

Men and women deal with pain differently, and women with red hair and fair skin respond better to painkillers than other people, a Canadian study has found.

The researchers, from McGill University in Montreal, found that the gene responsible for hair and skin colour – called Mc1r – is also involved in pain modulation in the brain, but only in women.

"Our data suggest that men and women modulate pain using different brain circuitry. We actually knew that this was true in mice for some 10 years or so, but now it appears to be true in people as well," wrote Professor Jeffrey Mogil to ABC Science Online in an email interview.

It has been known for some time that certain types of painkillers work only in women. This has been attributed to the painkillers targeting a specific pain pathway that have 'kappa-opioid' receptors present in women but not in men.

The researchers tried to find if having the Mc1r gene affected how pain is modulated. They gave an analgesic that targeted the kappa receptor to specially prepared mice that carried the 'redhead' gene.

As expected, the males and females in the control group of normal mice responded differently to the analgesic. But there was no difference in response between sexes of the mice with the 'redhead' gene.

This means it is the Mc1r gene that makes the differences between boys and girls when it comes to dealing with pain. The researchers then extended the experiments to people.

Mogil and colleagues gave a type of painkiller to a group of 42 people who had different natural hair and skin colours. They then subjected the people to a series of pain tests. In one, the subjects were given pulses of heat on their skin. In another, the researchers applied a tourniquet to the subject's arms and asked them to do handgrips until they could not stand the pain.

It turned out that 'classic' redheaded, fair skinned women responded better to the analgesic than any other group.

Establishing that there is a difference in the way men and women modulate pain may lead to a change in pain management. "If women and men really do have separate neural circuits modulating pain, then it should be possible to develop analgesics that literally work on one sex and not the other," said Mogil.

The group are now testing whether the Mc1r gene modulates morphine analgesia in a sex specific way. "If this is true, then it's an even bigger deal, because the vast majority of analgesics used for severe pain are mu-opioid analgesics like morphine," said Mogil.

The link between pain modulation and having red hair and fair skin is completely random, said Mogil. "Genes do more than one thing; it's a principle geneticist call 'pleiotropy'. I don't think one has anything to do with the other."

The findings were recently published in the Proceedings of the National Academy of Science.

Tags: business-economics-and-finance, health