Abstract
Objectives: To determine if the perceived high incidence of hypersensitivity to various substance in firomyalgia, including medications, due to abnormal P450 xenobiotic metabolism. Methods: The metabolism via two genetically polymorphic P450 pathways was determined for 33 fibromyalgia patients, and matched controls. Results: There was no statistical difference between the genotypic frequency of the CYP2D6 gene or phenotypic expression of CYP2C19 between patients and contorls. Conclusion: Xenobiotic metabolism by the two pathways studied is normal in fibromyalgia. Although other P450 pathways could conceivably be abnormal in fibromyalgia, we speculate that such hypersensitivity to multiple substances in these conditions is unlikely to be due to abnormal metabolism, and postulate instead that these symptoms are mediated by neural mechanisms.