Background: Morphine is a common analgesic often used to manage chronic pain, especially for patients with pain due to malignancies. Since UGT2B7 plays an important role in the metabolism of morphine, UGT2B7 gene mutation may influence the efficacy of morphine in patients with cancer being treated by this medication.
Aims: The aim of this study is to investigate the relationship between the polymorphisms of UGT2B7 and the efficacy of morphine treatment on cancer pain among the Chinese Han population.
Materials and methods: A total of 120 patients with cancer pain were enrolled in this study. Morphine was administrated through patient-controlled analgesia infusion pump, and the visual analog score (VAS) was used for pain assessment at 0.5, 4, 6, 12, 24, 48, and 72-h post morphine treatment, respectively. The plasma concentration of morphine and genetic polymorphism of UGT2B7 C802T and G221T was analyzed, respectively.
Results: The frequencies of UGT2B7 C802T were CC: 13.33%, CT: 45% and TT: 41.67%, and the frequencies of UGT2B7 G221T were GG: 76.67%, GT: 22.5% and TT: 0.83%. Moreover, the VAS score of patients with either C802T CT or TT was significantly higher than that in patients with C802T CC. However, no difference of VAS scores was observed between patients carrying G221T GG and patients carrying G221T GT. The plasma concentration of morphine for patients with the C802T CC was significantly lower than that in patients carrying C802T CT or TT, while there was no significant difference in the level of morphine between patients with G221T GG and G221T GT.
Conclusion: The polymorphism of UGT2B7 C802T, but not UGT2B7 G221T, has been associated with the efficacy of morphine treatment on cancer pain among Chinese Han population.
Keywords: Cancer pain; UGT2B7; morphine; polymorphism.