Do Redheads Really Require More Lidocaine?

So, is it fact or fiction? Are redheads really more resistant to anesthetic compared to the rest of the population? In a recent suturing and office procedures training session I attended, the speaker mentioned that redheads may require a greater amount of subcutaneous lidocaine for these procedures than other patients. Curious as to the veracity of this claim, I decided to do a little research. 

It turns out that research supports the reports of dentists, anesthesiologists and other healthcare providers that it takes more to anesthetize redheads. A 2006 Anesthesiology study suggests that redheads are more sensitive to both heat and cold pain perception and, that subcutaneous lidocaine is significantly less effective in this group. Similarly, a 2004 study published in the same journal indicates that redheads require about 20 percent more anesthesia than their dark haired or blonde counterparts. In 2005, researchers found yet more evidence to this effect publishing a study in Anesthesia showing specifically that redheads are more resistant to the anesthetic effects of subcutaneous lidocaine. Research published by dental groups has also shown that redheads have greater anxiety and fear of dental care than other groups of patients as a result of associated pain perception. 

Just why do redheads require more anesthesia than other patient populations? The cause lies in a gene mutation that affects hair color. Individuals with brown and blonde hair have a gene, the melanocortin-1 receptor (MC1R), that produces melanin. In redheads, a mutation in this MC1R gene results in red hair and fairer skin. The MC1R gene doesn’t act in isolation affecting only complexion. Rather, the gene also belongs to a family of receptors that includes pain receptors that modulate pain sensitivity. 

So, the next time you’re suturing a wound or performing an I&D, don’t forget to assess your patient’s hair color to help determine how much lidocaine you’ll need. 

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