Effect of Pregnane X Receptor*1B genetic polymorphisms on postoperative analgesia with fentanyl in Chinese patients undergoing gynecological surgery

Impacts of pregnane X receptor and cytochrome P450 oxidoreductase gene polymorphisms on trough concentrations of apixaban in patients with non-valvular atrial fibrillation

PURPOSE

We examined the impact of polymorphisms in genes encoding cytochrome P450 (CYP) 3A5 (gene code CYP3A5), P-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), cytochrome P450 oxidoreductase (POR), and pregnane X receptor (PXR; NR1I2) on the daily dose-adjusted steady-state trough concentrations (C_0h/D) of apixaban.

METHODS

The analyses included 104 patients with non-valvular atrial fibrillation (NVAF) undergoing AF catheter ablation. The CYP3A5*3; ABCG2 421C > A; ABCB1 1236C > T, 2677G > A/T, 3435C > T, and 2482-2236G > A; NR1I2 11156A > C, 11193T > C, and 8055C > T; and POR*28 genotypes were determined. The combination of the noted NR1I2 genotypes determined the PXR*1B haplotype.

RESULTS

Multiple linear regression analyses demonstrated that decreased creatinine clearance (Ccr) and the PXR*1B/*1B haplotype correlated with increased C_0h/D of apixaban, while the presence of the POR*28 allele correlated with decreased C_0h/D of apixaban (partial R² = 0.168, 0.029, and 0.044, all P < 0.05). The mean (95% CI) of estimated marginal means of apixaban C_0h/D calculated using Ccr as a covariate was the highest in POR*28 noncarriers with PXR*1B/*1B (23.5 [21.0-25.9] ng/mL/[mg/day]) and lowest in POR*28 carriers with other haplotypes (16.6 [15.5-17.7] ng/mL/[mg/day]).

CONCLUSION

The PXR*1B haplotype and POR*28 genotype statuses, which involve genes that impact the expression of multiple drug-metabolizing enzymes and drug-transporters, may have modest effects on the C_0h/D of apixaban, but these effects were found to be small.

PXR haplotype clusters will affect the pharmacokinetics of ciclosporin in Chinese renal transplant recipients

OBJECTIVE

PXR was reported to be the key nuclear receptor regulating the expression of metabolizing enzymes and transporters. The aim of this study was to evaluate the influence of PXR haplotype clusters on ciclosporin concentration in Chinese renal transplant recipients during the early stage after transplantation.

METHODS

A total of 98 recipients receiving ciclosporin were genotyped by PCR-RFLP, and the ciclosporin concentration was determined by EMIT.

KEY FINDINGS

The frequency of IVS2+55A>G, IVS2+78A>G, IVS6-17C>T, 1792A>G, 1944T>C and 2654T>C variant alleles was 0.343, 0.332, 0.378, 0.515, 0.520 and 0.393, which fitted Hardy-Weinberg equilibrium. Only the IVS6-17C>T and 2654T>C were significantly associated with the ciclosporin C₂ /D during the end of the first month. The mean ciclosporin C₂ /D level of the PXR*1B haplotype clusters was 1.3-fold and 1.2-fold higher compared with the *1A and *1C. No significant difference was observed in CsA C₂ /D between the PXR*1A and PXR*1C. We found no difference in C₀ /D among the six genotypes or the three haplotype clusters.

CONCLUSIONS

The PXR*1B in Chinese renal transplant patients was associated with ciclosporin concentration. Genetic polymorphisms and specific haplotype clusters in PXR could have significant contributory roles in affecting interethnic variations in drug disposition in the Chinese population.

Fentanyl overdoses and pharmacogenetics

Fentanyl has been implicated as a major contributor to the increased number of opioid overdose deaths. Surprisingly, little is known about the pharmacogenetic influences on fentanyl pharmacokinetics or pharmacodynamics. Pharmacogenetic studies of fentanyl are based largely on small sample sizes and have examined the potential association of only a small number of high frequency variants in selected candidate genes primarily with postoperative pain. Few data are available on low frequency variants, variants from racially/ethnically diverse populations, or on other phenotypes. Given the genetic diversity of low frequency variants, DNA sequencing may be needed to determine whether pharmacogenetic differences may contribute to lethal opioid overdoses.