Effect of the CYP2D6*10 C188T polymorphism on postoperative tramadol analgesia in a Chinese population.

Objective: The CYP2D6*10 allele is the most common allele with a frequency ranging from 51.3 to 70% and correlated with a significantly reduced metabolic activity in a Chinese population. The aim of the present study was to investigate whether the CYP2D6*10 allele has an impact on the postoperative analgesia effect of tramadol in Chinese patients recovering from major abdominal surgery.

Methods: A prospective study design was used and 70 gastric cancer patients recovering from gastrectomy were enrolled. After receiving a loading dose i.v., patients could self-administer doses of the drug combination (10 mg/ml tramadol plus 0.3 mg/ml metoclopramide) via patient-controlled analgesia (PCA). Blood samples were collected after induction of anesthesia. The CYP2D6*10 C188T polymorphism was analyzed by means of polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP). Demographic data among groups with different genotypes were analyzed using analysis of variance. The total consumption of tramadol between the three genotype groups for 48 h was compared.

Results: The allele frequency of CYP2D6*10 is 52.4%; patients were categorized into three groups according to the CYP2D6 genotype: patients without CYP2D6*10 (group I, n=17), patients heterozygous for CYP2D6*10 (group II, n=26), and patients homozygous for CYP2D6*10 (group III, n=20). The demographic data among the three groups were comparable. The total consumption of tramadol for 48 h in group III was significantly higher than that in groups I and II, while it did not differ between groups I and II.

Conclusions: This study indicates that the CYP2D6*10 allele has significant impact on analgesia with tramadol in a Chinese population. Pharmacogenetics may explain some of the varying responses to pain medication in postoperative patients.