The purpose of the study was to investigate the effects of the pregnane X receptor (PXR)*1B polymorphisms on CYP3A4 enzyme activity and postoperative fentanyl consumption in Chinese patients undergoing gynecological surgery.

PURPOSE:This study aimed to investigate whether CYP3A4*1G genetic polymorphism influences the metabolism of fentanyl in human liver microsomes in Chinese patients. METHODS:The human liver microsomes were obtained from 88 hepatobiliary surgery patients who accepted liver resection surgery in this study. A normal liver sample (confirmed by the Department of Pathology) was taken from the outer edge of the resected tissue. The metabolism of fentanyl in human liver microsomes was studied. The concentration of fentanyl was measured by high performance liquid chromatography. The CYP3A4*1G variant allele was genotyped using the PCR restriction fragment length polymorphism method. RESULTS:The frequency of the CYP3A4*1G variant allele was 0.188 in the 88 Chinese patients who had received hepatobiliary surgery. The metabolic rate of fentanyl in patients homozygous for the *1G/*1G variant (0.85 ± 0.37) was significantly lower than that in patients bearing the wild-type allele *1/*1 (1.89 ± 0.58) or in patients heterozygous for the *1/*1G variant (1.82 ± 0.65; p < 0.05). There were no gender-related differences in the metabolic rate of fentanyl (p > 0.05) nor was there any correlation between age and metabolic rate of fentanyl (p > 0.05). Results from different hepatobiliary diseases showed no significant difference in the metabolic rate of fentanyl (p > 0.05). The difference of CYP3A4 mRNA among different CYP3A4*1G variant alleles was significant (p < 0.05). There was positive correlation between CYP3A4 mRNA and metabolic rate of fentanyl (p < 0.01). CONCLUSIONS:CYP3A4*1G genetic polymorphism decreases the metabolism of fentanyl. There is a positive correlation between CYP3A4 mRNA level and metabolism of fentanyl.

Objective To investigate the effect of PXR* 1B polymorphism on postoperative analgesia with fentanyl in the patients undergoing gynecological operation.Methods A total of 102 female patients from Henan province, of Han nationality, aged 20-50 yr, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ , with body mass index of 14.8-30.0 kg/m2, scheduled for elective abdominal total hysterectomy or myomectomy under general anesthesia, were enrolled in this study.PXR genetic polymorphic sites were analyzed by polymerase chain reaction (PCR)-direct DNA sequencing.PXR* 1B haplotype was analyzed by the PHASE V.2.1 software.The patients were assigned into 3 groups according to their genotypes: PXR* 1B haplotype group (group PXR* 1B), non-PXR* 1B haplotype group (group n-PXR* 1B) and PXR* 1B/PXR * 1B group (group PXR* 1B/PXR* 1B).Postoperative pain was assessed with visual analogue scale (VAS) score.When VAS ＞ 3, fentanyl 20 μg was injected intermittently until VAS ≤ 3, and then a pump was connected to perform patient-controlled intravenous analgesia (PCIA) with fentanyl.PCIA solution contained fentanyl 1.0 mg and droperidol 5 mg in 100 ml of normal saline.The PCA pump was set up with a 2 ml bolus dose, a 5 min lockout interval and background infusion at a rate of 0.5 ml/h.The number of successfully delivered doses was set at 7 times, and the maximal amount of fentanyl was 145 μg.If exceeding the maximal dose, the VAS score was still more than 3, nonsteroidal anti-inflammatory drugs were given as rescue medication.VAS score immediately after the end of operation, and the consumption of fentanyl within 24 h after operation were recorded.Midazolam 0.1 mg/kg was injected intravenously during induction of general anesthesia, and 1 h later venous blood samples were collected for determination of plasma 1'-hydroxymidazolam and midazolam concentrations.The ratio of 1'-hydroxymidazolam concentration to midazolam concentration was calculated to reflect the activity of CYP3A4.Results No patients required rescue anesthetics in the three groups.There were 27 cases in group PXR * 1B, 53 cases in group n-PXR* 1B, and 22 cases in group PXR* 1B/PXR* 1B.PXR* 1B allele frequency was 37.2％.There was no significant difference in VAS score immediately after the end of operation, consumption of fentanyl within 24 h after operation, and activity of CYP3A4 between the three groups (P＞0.05).Conclusion PXR* 1B polymorphism has no effect on postoperative analgesia with fentanyl in the patients undergoing gynecological operation, and is not one of the genetic factors producing individual variation in postoperative analgesia.

Objective: To investigate the effect of doses of dexmedetomidine on patients to prevent fentanyl-induced cough during anesthesia induction.Methods: A total of 300 patients,scheduled for elective myomectomy or abdominal totai hysterectomy under general anesthesia,was randomly devided into 5 groups(n=60): Control group(group C) received infusion of 10 ml isotonic saline and treated groups(D1 to D4) were dexmedetomidine 0.10,0.25,0.5,1.0 μg/kg,over 10 min,before anesthesia induction.All groups subsequently received a fentanyl(4 μg/kg) intravenous push,over 2 s.The incidence and degree of cough were recorded within 1 min after fentanyl injection.Results: Compared with group C,the incidence of cough in D1~D4 groups were decreased,while the incidence of severe sinus bradycardia increased in D1~D4 groups(P<0.05).There were two humans having hypotension in D4 group.There was no significant difference in the incidence and the degree of the fentanyl-iuduced cough in D1~D4 groups.Conclusion: The iufusion of dexmedetomidine 0.1 μg/kg can effectively and savely prevent fentanyl-iuduced cough during anethesia induction.