Genetic polymorphisms of the human MDR1 drug transporter

Trends in Precision Medicine and Pharmacogenetics as an Adjuvant in Establishing a Correct Immunosuppressive Therapy for Kidney Transplant: An Up-to-Date Historical Overview

Kidney transplantation is currently the treatment of choice for patients with end-stage kidney diseases. Although significant advancements in kidney transplantation have been achieved over the past decades, the host's immune response remains the primary challenge, often leading to potential graft rejection. Effective management of the immune response is essential to ensure the long-term success of kidney transplantation. To address this issue, immunosuppressives have been developed and are now fully integrated into the clinical management of transplant recipients. However, the considerable inter- and intra-patient variability in pharmacokinetics (PK) and pharmacodynamics (PD) of these drugs represents the primary cause of graft rejection. This variability is primarily attributed to the polymorphic nature (genetic heterogeneity) of genes encoding xenobiotic-metabolizing enzymes, transport proteins, and, in some cases, drug targets. These genetic differences can influence drug metabolism and distribution, leading to either toxicity or reduced efficacy. The main objective of the present review is to report an historical overview of the pharmacogenetics of immunosuppressants, shedding light on the most recent findings and also suggesting how relevant is the research and investment in developing validated NGS-based commercial panels for pharmacogenetic profiling in kidney transplant recipients. These advancements will enable the implementation of precision medicine, optimizing immunosuppressive therapies to improve graft survival and kidney transplanted patient outcomes.

Multidrug resistance Gene-1 polymorphisms (C3435T and G2677T) and the risk of inflammatory bowel disease in Egyptian patients

BACKGROUND AND STUDY AIMS

The multidrug resistance 1 (MDR1) gene is a gene involved in the pathogenesis of inflammatory bowel disease (IBD).The aim of the study is to investigate the association of MDR-1 gene polymorphisms (C2345T and G2677T) and IBD incidence in Egyptian patients, and its relation with disease severity.

PATIENTS AND METHODS

This is a case-control study where genotyping of MDR-1 gene C3435T and G2677T single nucleotide polymorphisms (SNPs) were assayed.

RESULTS

Forty naïve IBD patients, who were composed of 25 UC and 15CD, were compared to 60 healthy controls. They were young aged with significant female predominance, particularly in CD (P = 0.004). UC was mainly (48 %) presented in moderate severity while CD was mainly (53.3 %) presented with mild severity. MDR-1 gene C3435T SNP was not statistically related to IBD, whether in terms of genotypes or alleles, yet its T allele was significantly related to moderate cases of UC (P = 0.014). However, GG genotype of G2677T SNP was significantly low in IBD (P = 0.013), while TT genotype and T allele were significantly related to CD (P = 0.011, and 0.012 respectively). Moreover, G allele proved to be associated significantly with moderate cases of UC (P = 0.001) and mild cases of CD (P = 0.002).

CONCLUSIONS

MDR-I gene G2677T SNP GG genotype proved to be protective against IBD, thus may be considered in diagnostic workup of IBD including its severity.

Innovation in cancer pharmacotherapy through integrative consideration of germline and tumor genomes

Precision cancer medicine is widely established, and numerous molecularly targeted drugs for various tumor entities are approved or are in development. Personalized pharmacotherapy in oncology has so far been based primarily on tumor characteristics, for example, somatic mutations. However, the response to drug treatment also depends on pharmacological processes summarized under the term ADME (absorption, distribution, metabolism, and excretion). Variations in ADME genes have been the subject of intensive research for >5 decades, considering individual patients' genetic makeup, referred to as pharmacogenomics (PGx). The combined impact of a patient's tumor and germline genome is only partially understood and often not adequately considered in cancer therapy. This may be attributed, in part, to the lack of methods for combined analysis of both data layers. Optimized personalized cancer therapies should, therefore, aim to integrate molecular information, which derives from both the tumor and the germline genome, and taking into account existing PGx guidelines for drug therapy. Moreover, such strategies should provide the opportunity to consider genetic variants of previously unknown functional significance. Bioinformatic analysis methods and corresponding algorithms for data interpretation need to be developed to integrate PGx data in cancer therapy with a special meaning for interdisciplinary molecular tumor boards, in which cancer patients are discussed to provide evidence-based recommendations for clinical management based on individual tumor profiles. SIGNIFICANCE STATEMENT: The era of personalized oncology has seen the emergence of drugs tailored to genetic variants associated with cancer biology. However, the full potential of targeted therapy remains untapped owing to the predominant focus on acquired tumor-specific alterations. Optimized cancer care must integrate tumor and patient genomes, guided by pharmacogenomic principles. An essential prerequisite for realizing truly personalized drug treatment of cancer patients is the development of bioinformatic tools for comprehensive analysis of all data layers generated in modern precision oncology programs.

Analysis of ABCB1 Gene Polymorphisms and Their Impact on Tacrolimus Blood Levels in Kidney Transplant Recipients

Tacrolimus (Tc) is an immunosuppressant used in transplant patients, but its therapeutic range is narrow, making precise dosing essential. This study investigates the association of three single nucleotide polymorphisms (SNPs) (ABCB1 3435C>T, 1236C>T, 2677G>T/A) with Tc levels over time to gain better insights into their role in personalized medicine. We conducted the study over four distinct periods: 1-14 days, 15-30 days, 31-60 days, and beyond 60 days post-transplantation. The analysis included allele, genotype, haplotype, and diplotype frequencies of the three SNPs concerning Tc blood levels. Statistical significance was determined, and false discovery rate (PFDR) correction was applied where appropriate. Significant associations were found between the C (ABCB1 C1236T), A alleles (ABCB1 G2677T/A), the CAC haplotype and lower Tc levels. The CAC-TGT and TGT-TGT diplotypes significantly influence how patients metabolize the drug. The TGT haplotype and the AA genotype (ABCB1 G2677T/A) were associated with higher Tc levels, suggesting a long-term genetic influence. Genetic factors, specifically certain SNPs and diplotypes, significantly impact Tc blood levels, with their influence varying over time.

Association of ABCB1(Rs10276036, C/T) Gene, IL-18, and TNFα as Risk Factors for Nephrotic Syndrome Incidence

Background

The most common cause of Nephrotic Syndrome (NS) in children is idiopathic NS, also called nephrosis. The most prominent clinical signs are hyperlipidemia, severe proteinuria, edema, swelling of body tissues, and an increased risk of infection. The object of this study was to examine the correlation of the ABCB1 gene (rs10276036, C > T), IL-18, and TNFα to the prevalence of NS among Egyptian children having NS.

Methods

This study included 100 participants with NS and 100 healthy controls. To analyze the ABCB1 gene (rs10276036 C >T) variant PCR technique was used. IL-18 and TNF levels were estimated using Enzyme-Linked Immunosorbent Assay (ELISA).

Results

Increased frequency of CT and TT genotypes of the ABCB1 gene (rs10276036 C / T) in NS patients compared to controls, with p-value = 0.001, OR = 2.270, CI = (1.550-3.327) for CT genotype and p-value = 0.001, OR = 5.070, CI = (2.463-10.438) for TT genotype. The frequencies of ABCB1 (rs10276036 C >T) genotypes were statistically significant in the dominant model (OR 2.560; p< 0.001) and in the recessive model OR, 3.231; p= 0.001). Significantly high levels of both IL-18 and TNFα were found in NS patients compared to controls.

Conclusions

The ABCB1gene (rs10276036 C/T), IL-18, and TNFα are associated with the prevalence of NS in Egyptian children and might be considered as independent risk factors for its incidence.

Regulation of P-Glycoprotein during Oxidative Stress

P-glycoprotein (Pgp, ABCB1, MDR1) is an efflux transporter protein that removes molecules from the cells (outflow) into the extracellular space. Pgp plays an important role in pharmacokinetics, ensuring the absorption, distribution, and excretion of drugs and its substrates, as well as in the transport of endogenous molecules (steroid and thyroid hormones). It also contributes to tumor cell resistance to chemotherapy. In this review, we summarize the mechanisms of Pgp regulation during oxidative stress. The currently available data suggest that Pgp has a complex variety of regulatory mechanisms under oxidative stress, involving many transcription factors, the main ones being Nrf2 and Nf-kB. These factors often overlap, and some can be activated under certain conditions, such as the deposition of oxidation products, depending on the severity of oxidative stress. In most cases, the expression of Pgp increases due to increased transcription and translation, but under severe oxidative stress, it can also decrease due to the oxidation of amino acids in its molecule. At the same time, Pgp acts as a protector against oxidative stress, eliminating the causative factors and removing its by-products, as well as participating in signaling pathways.

[Clinical effectiveness and pharmacokinetics of gliflozin from the point of view of individual genetic characteristics: A review]

A review of publications devoted to the analysis of genetic polymorphisms and features of the functioning of genes that affect the pharmacokinetics and pharmacodynamics of sodium-glucose cotransporter-2 inhibitors (SGLT2i) is presented. Objective of the study was to reveal information about genes whose polymorphism may affect the effectiveness of SGLT2i. The review was carried out in accordance with the PRISMA 2020 recommendations, the search for publications was carried out in the PubMed databases (including Medline), Web of Science, as well as Russian scientific electronic libraries eLIBRARY.RU from 1993 to 2022. Polymorphisms in the structure of several genes (SLC5A2, UGT1A9, ABCB1, PNPLA3) have been described that may affect the treatment of type 2 diabetes mellitus complicated by diseases such as chronic heart failure, chronic kidney disease, or non-alcoholic fatty liver disease. The information found on the genetic features of the development of the effects of SGLT2i is limited to a description of the differences in their pharmacokinetics. The relevance of currently available pharmacogenetic studies is largely constrained by small sample sizes.

An Improved Technique for Genotyping the ABCB1 Gene Variant of Exon 21

The Multidrug Resistance protein (ABCB1, MDR1) is involved in the transport of xenobiotics and antiretroviral drugs. Some variants of the ABCB1 gene are of clinical importance; among them, exon 12 (c.1236C>T, rs1128503), 21 (c.2677G>T/A, rs2032582), and 26 (c.3435C>T, rs1045642) have a high incidence in Caucasians. Several protocols have been used for genotyping the exon 21 variants, such as allele-specific PCR-RFLP using adapted primer to generate a digestion site for several enzymes and automatic sequencing to detect the SNVs, TaqMan Allele Discrimination assay and High-Resolution Melter analysis (HRMA). The aim was to describe a new approach to genotype the three variants c.2677G>T/A for the exon 21 doing only one PCR with the corresponding primers and the digestion of the PCR product with two restriction enzymes: BrsI to identify A allele and BseYI to differentiate between G or T. An improvement of this methodology was also described. The proposal technique here described is demonstrated to be very efficient, easy, fast, reproducible, and cost-effective.

A major locus confers triclabendazole resistance in Fasciola hepatica and shows dominant inheritance

Fasciola hepatica infection is responsible for substantial economic losses in livestock worldwide and poses a threat to human health in endemic areas. The mainstay of control in livestock and the only drug licenced for use in humans is triclabendazole (TCBZ). TCBZ resistance has been reported on every continent and threatens effective control of fasciolosis in many parts of the world. To date, understanding the genetic mechanisms underlying TCBZ resistance has been limited to studies of candidate genes, based on assumptions of their role in drug action. Taking an alternative approach, we combined a genetic cross with whole-genome sequencing to localise a ~3.2Mbp locus within the 1.2Gbp F. hepatica genome that confers TCBZ resistance. We validated this locus independently using bulk segregant analysis of F. hepatica populations and showed that it is the target of drug selection in the field. We genotyped individual parasites and tracked segregation and reassortment of SNPs to show that TCBZ resistance exhibits Mendelian inheritance and is conferred by a dominant allele. We defined gene content within this locus to pinpoint genes involved in membrane transport, (e.g. ATP-binding cassette family B, ABCB1), transmembrane signalling and signal transduction (e.g. GTP-Ras-adenylyl cyclase and EGF-like protein), DNA/RNA binding and transcriptional regulation (e.g. SANT/Myb-like DNA-binding domain protein) and drug storage and sequestration (e.g. fatty acid binding protein, FABP) as prime candidates for conferring TCBZ resistance. This study constitutes the first experimental cross and genome-wide approach for any heritable trait in F. hepatica and is key to understanding the evolution of drug resistance in Fasciola spp. to inform deployment of efficacious anthelmintic treatments in the field.

Some New Aspects of Genetic Variability in Patients with Cutaneous T-Cell Lymphoma

AIM

Cutaneous T-cell lymphoma (CTCL) is a group of T-cell malignancies that develop in the skin. Though studied intensively, the etiology and pathogenesis of CTCL remain elusive. This study evaluated the survival of CTCL patients in the 1st Department of Dermatovenereology of St. Anne's University Hospital Brno. It included analysis of 19 polymorphic gene variants based on their expected involvement in CTCL severity.

MATERIAL AND METHODS

75 patients with CTCL, evaluated and treated at the 1st Department of Dermatovenereology of St. Anne´s University Hospital Brno, Faculty of Medicine, Masaryk University, were recruited for the study over the last 28 years (44 men and 31 women, average age 58 years, range 20-82 years). All patients were genotyped for 19 chosen gene polymorphisms by the conventional PCR method with restriction analysis. A multivariate Cox regression model was calculated to reveal genetic polymorphisms and other risk factors for survival.

RESULTS

The model identified MDR Ex21 2677 (rs2032582) as a significant genetic factor influencing the survival of the patients, with the T-allele playing a protective role. A multivariate stepwise Cox regression model confirmed the following as significant independent risk factors for overall survival: increased age at admission, clinical staging of the tumor, and male sex.

CONCLUSION

We showed that the TT genotype at position 2677 of the MDR1 gene exhibited statistically significant longer survival in CTCL patients. As such, the TT genotype of MDR1 confers a significant advantage for the CTCL patients who respond to treatment.

Common ABCB1 SNP, C3435T could affect systemic exposure of dapagliflozin in healthy subject

P-glycoprotein (P-gp) is a transporter that plays an excretory role in epithelial cells. It is encoded by ABCB1, and single nucleotide polymorphisms (SNPs) in this gene can affect systemic drug exposure. Dapagliflozin and sitagliptin, used in type 2 diabetes treatment, are P-gp substrates. Here, we aimed to investigate whether ABCB1 polymorphisms affect dapagliflozin and sitagliptin pharmacokinetics (PK) in healthy Korean subjects. The study population consisted of 100 healthy Korean subjects (94 men and 6 women) who participated in four different clinical trials and received dapagliflozin and sitagliptin doses of 10 and 100 mg, respectively. We determined ABCB1 genotypes for the C3435T, C1236T, and G2677T/A SNPs. The relationship between the genotypes and dapagliflozin PKs was examined. Dapagliflozin and sitagliptin PK parameters were not statistically significantly affected by ABCB1 SNP genotypes. However, homozygous 3435TT subjects showed higher dapagliflozin PK parameters than CT and CC subjects. In subjects with the 3435TT and those with 3435CC and 3435CT genotypes, mean C_max, AUC_inf, and AUC_0-1 values of dapagliflozin were 223.06 ng/mL and 194.81 ng /mL (p = 0.2767), 673.58 ng*h/mL and 573.96 ng*h/mL (p = 0.0492), and 128.53 ng*h/mL and 104.61 ng*h/mL (p = 0.2678), respectively. In summary, dapagliflozin and sitagliptin PK parameters were not significantly different between individuals with C1236T and C2677T/A ABCB1 genetic polymorphisms. Dapagliflozin exhibited higher systemic exposure in 3435TT subjects than in CC/CT subjects.

Influence of eight ABCB1 polymorphisms on antidepressant response in a prospective cohort of treatment-free Russian patients with moderate or severe depression: An explorative psychopharmacological study with naturalistic design

BACKGROUND

Many antidepressants are substrates of P-glycoprotein, an efflux transporter in the blood-brain-barrier encoded by the ABCB1 gene. Genetic variations might influence the transport rate of antidepressants and hence their pharmacological effects. This study investigates the influence of eight polymorphisms in the ABCB1 gene on antidepressant treatment response.

METHOD

152 patients were included from psychiatric departments of the Mental Health Research Institute in Tomsk. The difference in Hamilton-Depression-Rating-Scale (HAMD-17)-scores between baseline and week two, week two and four, and baseline and week four was used to estimate timing of improvement of depression. Associations between the ABCB1 gene-polymorphisms and reduction in HAMD-17 score were assessed using independent t-test and multiple linear regression.

RESULTS

Tricyclic antidepressants were associated with a higher reduction of HAMD-17 score when compared to SSRIs. The SNP rs2235040 A-allele had a significant positive influence on the ΔHAMD-17_(0→2W) score but a significant negative influence on the ΔHAMD-17_(2→4W) score. The rs4148739 G-allele had a significant negative influence on the ΔHAMD-17_(0→2W) score but a significant positive influence on the ΔHAMD-17_(2→4W) score. The SNP rs2235015 T-allele is significant negatively related to the ΔHAMD-17_(2→4W) score.

CONCLUSION

ABCB1 Genetic variations appear to affect speed but not magnitude of antidepressant drug response.

Effects of genetic polymorphism of drug-metabolizing enzymes on the plasma concentrations of antiepileptic drugs in Chinese population

As a chronic brain disease, epilepsy affects ~50 million people worldwide. The traditional antiepileptic drugs (AEDs) are widely applied but showing various problems. Although the new AEDs have partially solved the problems of traditional AEDs, the current clinical application of traditional AEDs are not completely replaced by new drugs, particularly due to the large individual differences in drug plasma concentrations and narrow therapeutic windows among patients. Therefore, it is still clinically important to continue to treat patients using traditional AEDs with individualized therapeutic plans. To date, our understanding of the molecular and genetic mechanisms regulating plasma concentrations of AEDs has advanced rapidly, expanding the knowledge on the effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of AEDs. It is increasingly imperative to summarize and conceptualize the clinical significance of recent studies on individualized therapeutic regimens. In this review, we extensively summarize the critical effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of several commonly used AEDs as well as the clinical significance of testing genotypes related to drug metabolism on individualized drug dosage. Our review provides solid experimental evidence and clinical guidance for the therapeutic applications of these AEDs.

Clinical Importance of Potential Genetic Determinants Affecting Propofol Pharmacokinetics and Pharmacodynamics

Interindividual variability in response to drugs used in anesthesia has long been considered the rule, not the exception. It is important to mention that in anesthesiology, the variability in response to drugs is multifactorial, i.e., genetic and environmental factors interact with each other and thus affect the metabolism, efficacy, and side effects of drugs. Propofol (2,6-diisopropylphenol) is the most common intravenous anesthetic used in modern medicine. Individual differences in genetic factors [single nucleotide polymorphisms (SNPs)] in the genes encoding metabolic enzymes, molecular transporters, and molecular binding sites of propofol can be responsible for susceptibility to propofol effects. The objective of this review (through the analysis of published research) was to systematize the influence of gene polymorphisms on the pharmacokinetics and pharmacodynamics of propofol, to explain whether and to what extent the gene profile has an impact on variations observed in the clinical response to propofol, and to estimate the benefit of genotyping in anesthesiology. Despite the fact that there has been a considerable advance in this type of research in recent years, which has been largely limited to one or a group of genes, interindividual differences in propofol pharmacokinetics and pharmacodynamics may be best explained by the contribution of multiple pathways and need to be further investigated.

Association of ABCB1 polymorphisms with carbamazepine metabolism and resistance in epilepsy: A meta-analysis

OBJECTIVE

ABCB1 polymorphisms were previously demonstrated to be associated with the metabolism and resistance of carbamazepine (CBZ) in epilepsy, but the results still remained controversial. Therefore, we performed this meta-analysis to further evaluate the impacts of ABCB1 polymorphisms on CBZ metabolism and resistance.

METHODS

The PubMed, EMBASE, Cochrane library, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals Database and Wan Fang Database were searched for eligible publications up to 5 July 2021. The mean difference (MD), Odds ratio (OR) and 95 % confidence interval (CI) were calculated by Review Manager 5.3 software to assess the strength of the association.

RESULTS

Twelve studies involving 2126 epilepsy patients were included in this meta-analysis. We found that the TC genotype (heterozygous model: TC vs. CC) of rs1045642 polymorphism was significantly connected with decreased CBZ concentration. Furthermore, this polymorphism was indicated to be associated with concentrations of carbamazepine-10, 11-epoxide (homozygote model: TT vs. CC; heterozygous model: TC vs CC; dominant model: TT + TC vs. CC; over-dominant model: TC vs. TT + CC) and carbamazepine-10, 11-trans dihydrodiol (heterozygous model: TC vs. CC; dominant model: TT + TC vs. CC). Moreover, the AG genotype of rs2032582 polymorphism was related to increased CBZ concentration in heterozygous (AG vs. GG), dominant (AA + AG vs. GG) and over-dominant (AG vs. AA + GG) models. Additionally, rs1128503 was associated with CBZ resistance in heterozygous model (TC vs. CC).

CONCLUSIONS

ABCB1 rs1045642 and rs2032582 polymorphisms were associated with CBZ metabolism for epilepsy, and rs1128503 was related to CBZ resistance. These findings would contribute to improving individualized therapy of epileptic patients.

Effects of genetic polymorphisms of ABCB1 on the efficacy of anesthetic and analgesic agents: a systematic review

Aim: To perform a systematic review to determine the effect of ABCB1 (1236C>T, 2677G>T/A and 3435C>T) variants on the effects of anesthetic and analgesic agents in various surgical procedures. Materials & methods: Literature was obtained from established databases and reference tracking. The main outcome measures were efficacy of anesthetic and analgesic agents intraoperative or within 48 h post surgery of human population. Results: Seventeen studies were included for data extraction from 1127 screened studies. The influences of ABCB1 gene polymorphisms on analgesic effects showed conflicting results. The mutational homozygous TT genotypes of 1236C>T and 3435C>T polymorphisms demonstrated significant association with the anesthetic effects. Conclusion: The mutational homozygous TT genotype in both ABCB1 1236C>T and 3435C>T is associated with weaker anesthetic effect but there are no clearly demonstrated analgesic effects.

C3435T Polymorphism of the ABCB1 Gene in Polish Patients with Inflammatory Bowel Disease: A Case-Control and Meta-Analysis Study

P-glycoprotein encoded by the ABCB1 gene constitutes a molecular barrier in the small and large bowel epithelium, and its different expression may influence susceptibility to inflammatory bowel disease (IBD). We aimed to assess the contribution of the C3435T polymorphism to disease risk in the Polish population. A total of 100 patients (50 Crohn's disease (CD), 50 ulcerative colitis (UC)) and 100 healthy controls were genotyped for the single nucleotide polymorphism (SNP) C3435T by using the PCR-RFLP method. Patients were classified on the basis of disease phenotype and the specific treatment used. A meta-analysis was carried out of our results and those from previously published Polish studies. There was no significant difference in allele and genotype frequencies in IBD patients compared with controls. For CD patients, a lower frequency of TT genotype in those with colonic disease, a lower frequency of T allele, and a higher frequency of C allele in those with luminal disease were observed, whereas for UC patients, a lower frequency of CT genotype was observed in those with left-sided colitis. A meta-analysis showed a tendency towards higher prevalence of CC genotype in UC cases. These results indicate that the C3435T variants may confer a risk for UC and influence disease behaviour.

R-CHOP resistance in diffuse large B-cell lymphoma: biological and molecular mechanisms

Although the first-line rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone regimen (R-CHOP) substantially improved outcomes for patients with diffuse large B-cell lymphoma (DLBCL), 40% of the patients suffered from relapsed/refractory disease and had poor survival outcomes. The detailed mechanism underlying R-CHOP resistance has not been well defined. For this review, we conducted a thorough search for literature and clinical trials involving DLBCL resistance. We discussed DLBCL biology, epigenetics, and aberrant signaling of the B-cell receptor (BCR), phosphatidylinositol 3-kinase (PI3K)/Akt, nuclear factor kappa light chain enhancer of activated B-cells (NF-κB), and the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) pathways as defining mechanisms of DLBCL heterogeneity and R-CHOP resistance. The cell of origin, double- or triple-hit lymphoma and double-protein-expression, clonal evolution, tumor microenvironment, and multi-drug resistance help to contextualize DLBCL resistance in an (epi)genetically and biologically comparative manner. With better understanding of the biological and molecular landscape of DLBCL, a more detailed classification system and tailored treatments will ideally become available to further improve the prognosis of DLBCL patients.

ABCB1 c.2677G>T/c.3435C>T diplotype increases the early-phase oral absorption of losartan

Losartan has been shown to be a substrate of the drug-efflux transporter MDR1, encoded by the ABCB1 gene. ABCB1 c.2677G>T and c.3435C>T variants are known to be associated with reduced expression and function of P-glycoprotein (P-gp). We investigated the effects of ABCB1 diplotype on the pharmacokinetics of losartan. Thirty-eight healthy Korean volunteers with different ABCB1 diplotypes [c.2677G> T and c.3435C>T; carriers of GG/CC (n = 13), GT/CT (n = 12) and TT/TT (n = 13) diplotype] were recruited and administered a single 50 mg oral dose of losartan potassium. Losartan and its active metabolite E-3174 samples in plasma and urine were collected up to 10 and 8 h after drug administration, respectively, and the concentrations of both samples were determined by HPLC method. Significant differences were observed in C_max of losartan and losartan plus E-3174 (Lo + E) among the three diplotype groups (both P < 0.01). However, the power of the performed test is less than the desired power (0.800). The t_max of losartan and E-3174 in three diplotype groups were also significantly different (both P < 0.01). The AUC values of Lo + E were significantly different among the three diplotype groups until 6 h after losartan administration (P < 0.01). On the contrary, AUC at the periods of 8-10 h and 10 h-infinity of Lo + E were significantly lower in the TT/TT group than in the GG/CC group. Urinary excretion of losartan until 4 h after losartan administration in the TT/TT group was higher than that of the GG/CC group. These results suggest that c.2677G>T/c.3435C>T diplotypes of ABCB1 may significantly increase the early-phase absorption of losartan, but not the total absorption.

Combinations of common SNPs of the transporter gene ABCB1 influence apparent bioavailability, but not renal elimination of oral digoxin

Effects of different genotypes on the pharmacokinetics of probe substrates may support their use as phenotyping agents for the activity of the respective enzyme or transporter. Digoxin is recommended as a probe substrate to assess the activity of the transporter P-glycoprotein (P-gp) in humans. Current studies on the individual effects of three commonly investigated single nucleotide polymorphisms (SNPs) of the ABCB1 gene encoding P-gp (C1236T, G2677T/A, and C3435T) on digoxin pharmacokinetics are inconclusive. Since SNPs are in incomplete linkage disequilibrium, considering combinations of these SNPs might be necessary to assess the role of polymorphisms in digoxin pharmacokinetics accurately. In this study, the relationship between SNP combinations and digoxin pharmacokinetics was explored via a population pharmacokinetic approach in 40 volunteers who received oral doses of 0.5 mg digoxin. Concerning the SNPs 1236/2677/3435, the following combinations were evaluated: CGC, CGT, and TTT. Carriers of CGC/CGT and TTT/TTT had 35% higher apparent bioavailability compared to the reference group CGC/CGC, while no difference was seen in CGC/TTT carriers. No significant effect on renal clearance was observed. The population pharmacokinetic model supports the use of oral digoxin as a phenotyping substrate of intestinal P-gp, but not to assess renal P-gp activity.

Perplexing Role of P-Glycoprotein in Tumor Microenvironment

Development of multidrug resistance (MDR) still remains a major obstacle to the long-term success of cancer therapy. P-glycoprotein (P-gp) is a well-identified membrane transporter with capability to efflux drug molecules out of the cancer cell leading to reduced efficiency of chemotherapy. Cancer cells upregulate P-gp expression as an adaptive response to evade chemotherapy mediated cell death. While several P-gp inhibitors have been discovered by in silico and pre-clinical studies, very few have successfully passed all phases of the clinical trials. Studies show that application of P-gp inhibitors in cancer therapy regimen following development of MDR achieved limited beneficial outcomes. While, the non-specific substrate binding to P-gp has made the drug-design a challenge, a bigger perplexing challenge comes from its role in tumor immunology. Expression of P-gp was noted immune cell phenotypes with apparently antagonistic functionality. Both pro-tumor MΦ2-macrophages and, anti-tumor NK-cell and Th17/CD4⁺T cell subsets have shown enhanced expression of P-gp. While drug based inhibition of P-gp in pro-tumor immune cell phenotypes could promote tumor elimination, however, it would not be a rational choice to exert inhibition of P-gp on anti-tumor immune cell phenotypes. This mutually exclusive paradigm of P-gp functionality requires a more comprehensive and detailed understanding of its role in tumor microenvironment with active interplay of cancer and immune cells in the tumor mileu. In this review, we focus on the current understanding of the role of P-gp in cancer cells and immune cells and finally attempt to highlight some caveats in the current understanding of its role in comprehensive tumor microenvironment along with challenges in the development of P-gp inhibitors toward anti-cancer therapy.

Crohn's Disease Is Associated with Decreased CYP3A4 and P-Glycoprotein Protein Expression

Cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp) have broad substrate overlap and are involved in the metabolism and transport of nearly 50% of currently prescribed medications. In the intestine, CYP3A4 and P-gp are coexpressed in the enterocytes at the intestinal villous tip and act in a coordinated manner to limit drug and xenobiotic oral bioavailability prior to further metabolism and disposition in the liver. Crohn's disease (CD), a form of inflammatory bowel disease, introduces a transmural intestinal insult that disrupts the intestinal barrier function; it therefore has the potential to affect intestinal drug metabolism and transport. We hypothesized that individuals with CD have reduced intestinal expression of CYP3A4 and P-gp. We obtained intestinal biopsy samples from individuals with and without CD and quantified the expression of CYP3A4 and P-gp. When we carried out Western analysis for protein expression, we observed a significant reduction in ileal (45% decrease) and colonic (78% decrease) CYP3A4 protein expression in subjects with CD compared with those without. Similarly, an 85% reduction in colonic P-gp protein expression was seen in the CD patients. Our data highlight important and novel findings pertaining to CD-associated changes to the intestinal expression of CYP3A4 and P-gp that are of relevance to better predict substrate drug dosing for patients with CD.

Individualized treatment based on CYP3A5 single-nucleotide polymorphisms with tacrolimus in ulcerative colitis

Background/Aims

The pharmacokinetics of tacrolimus (TAC) is known to be largely influenced by single-nucleotide polymorphisms (SNPs) in CYP3A5. Patients starting TAC require careful dose adjustment, owing to the wide range of optimal dosages, depending on their CYP3A5 expression status. Here, we evaluated whether individualization of TAC dosages based on CYP3A5 SNPs would improve its therapeutic efficacy in ulcerative colitis.

Methods

Twenty-one patients were prospectively treated, with their initial dosage adjusted according to their CYP3A5 status (0.1, 0.15, and 0.2 mg/kg/day for CYP3A5*3/*3, CYP3A5*1/*3, and CYP3A5*1/*1, respectively). Their clinical outcomes were compared with those of patients treated with a fixed dose (0.1 mg/kg/day).

Results

The first blood trough level of CYP3A5 expressors, CYP3A5*1/*3 or CYP3A5*1/*1, and the overall rate in achieving the target blood trough level within a week in the individualized-dose group were significantly higher than those in the fixed-dose group (5.15±2.33 ng/mL vs. 9.63±0.79 ng/mL, P=0.035 and 12.5% vs. 66.7%, P=0.01). The remission rate at 2 weeks in the expressors was as high as that in the nonexpressors, CYP3A5*3/*3, in the individualized-dose group.

Conclusions

Individualized TAC treatment is effective against ulcerative colitis regardless of the CYP3A5 genotype.

ATP-Binding Cassette Transporters in the Clinical Implementation of Pharmacogenetics

ATP-binding cassette (ABC) transporters are involved in a large number of processes and contribute to various human genetic diseases. Among other functions, ABC proteins are involved in the transport of multiple drugs through cells. Most of the genes coding for these transporters are highly polymorphic and DNA variants in these genes can affect the normal functioning of these proteins, affecting the way drugs are transported, increasing or decreasing drug levels. These changes in the intracellular and extracellular drug levels may be associated with altered drug effectiveness or severe drug-induced adverse events. This review presents a state-of-art of the most pharmacogenetics clinically relevant ABC transporters closed to the clinical implementation.

Prolactin levels: sex differences in the effects of risperidone, 9-hydroxyrisperidone levels, CYP2D6 and ABCB1 variants

AIM

The role of sex on the association of plasma prolactin levels with risperidone (R) and 9-hydroxyrisperidone (9-OHR) concentrations is investigated.

METHODS

Plasma R and prolactin concentrations, CYP2D6 and exon 21 and 26 ABCB1 gene variants were studied in 110 patients.

RESULTS

In females, a 1 ng/ml increase in R levels was associated with a significant 1.02% increase in prolactin levels. In males, a 1 ng/ml increase in 9-OHR levels was associated with a significant 1.18% increase in prolactin levels. ABCB1 haplotype 12 had significant but opposite effects in males and females. In the combined sample, 9-OHR, but not R levels had significant effects on prolactin levels.

CONCLUSION

Genes had sex-specific effects on risperidone-associated prolactin elevations.

A case report of mesenteric heterotopic ossification: Histopathologic and genetic findings

Mesenteric heterotopic ossification (MHO) is very rare and occurs in mid- to late-adulthood, usually in the context of prior abdominal surgery. The mechanisms of MHO are unknown. Here we describe the case of a 72-year-old man with MHO. Standard histological staining revealed that MHO occurred through an endochondral process. By comparison to known mutations in genetic conditions of HO such as fibrodysplasia ossificans progressiva (FOP) and progressive osseous heteroplasia (POH), DNA sequencing analysis demonstrated the presence of a commonly occurring heterozygous synonymous polymorphism (c.690G>A; E230E) in the causative gene for FOP (ACVR1/ALK2). However, no frameshift, missense, or nonsense mutations in ACVR1, or in the causative gene for POH (GNAS), were found. Although genetic predisposition may play a role in MHO, our data suggest that mutations which occur in known hereditary conditions of HO are not the primary cause.

Genetic risk factors for chemotherapy-induced nausea and vomiting in patients with cancer receiving cisplatin-based chemotherapy

PURPOSE

Younger age and female sex have already been well-known risk factors for chemotherapy-induced nausea and vomiting (CINV), and 30-50% of cancer patients still suffer from CINV. Genetic polymorphisms are suggested to influence antiemetic treatment response.

METHODS

This study included a subset of patients previously enrolled in a randomised controlled trial; 156 patients were evaluated. This study aimed to evaluate the role of pharmacogenomic polymorphisms relevant to antiemetic response in patients with cancer receiving cisplatin-based chemotherapy. The study's efficacy endpoint was the proportion of patients with complete response (CR). The study endpoint was evaluated separately in the acute (CR_0-24) and delayed (CR_24-120) phases. Thirteen polymorphisms were genotyped, and the association of these genotypes with the efficacy of prophylactic antiemetics was then investigated. Confounding variables for the CR were identified using stepwise multivariate logistic regression analysis. Age and sex were included as independent variables by the forced-entry method, and the stepwise method was used to select the pharmacogenomic factors for inclusion as independent variables.

RESULTS

Multivariate logistic regression analysis revealed that the ERCC1 8092AA (odds ratio [OR] = 11.25; 95% confidence interval [CI] 1.74-72.71; p = 0.011) and female sex (OR = 3.63; 95% CI 1.14-11.58; p = 0.029) were significant predictors of CR_0-24. No significant association of CR_24-120 with pharmacogenomic polymorphisms was found via multivariate logistic regression analysis.

CONCLUSIONS

ERCC1 polymorphism influenced the extent of CINV control in patients receiving cisplatin-based chemotherapy.

TRIAL REGISTRATION

Clinical trial information: UMIN 000009335.

ATP-binding cassette subfamily B member 1 1236C/T polymorphism significantly affects the therapeutic outcome of tacrolimus in patients with refractory ulcerative colitis

BACKGROUND AND AIM

Tacrolimus is now considered to be one of the main therapeutic options for refractory ulcerative colitis. Both cytochrome P-450 3A5 (CYP3A5) and ATP-binding cassette subfamily B member 1 (ABCB1) associated with tacrolimus metabolism are known to have several genetic polymorphisms. However, it remains controversial whether these polymorphisms affect the therapeutic efficacy for ulcerative colitis. We aimed to investigate the influence of both CYP3A5 and ABCB1 polymorphisms on the efficacy of tacrolimus in ulcerative colitis treatment under the tight dose-adjusting strategy.

METHODS

Sixty-one Japanese patients with ulcerative colitis treated with tacrolimus were enrolled retrospectively. Tacrolimus treatment was performed using the tight dose-adjusting strategy. Genotyping for CYP3A5*3, ABCB1 1236C>T, 2677G>A,T, and 3435C>T were performed, and the clinical outcomes at 12 weeks after the initiation of tacrolimus were compared among the genotypes.

RESULTS

There was no association between the CYP3A5 genotypes and therapeutic efficacy. In contrast, a significant association was observed with the ABCB1 1236C > T polymorphism and therapeutic efficacy. The ABCB1 1236CC+CT groups (n = 41) had a significantly higher response rate (73% vs 35%; P = 0.004) and remission rate (61% vs 20%; P = 0.002) than the TT group (n = 20). The multivariate logistic regression analysis also revealed that ABCB1 1236C>T was identified as an independent factor associated with remission.

CONCLUSIONS

ABCB1 1236C>T polymorphism significantly affects the therapeutic efficacy of tarcolimus at 12 weeks under the tight dose-adjusting treatment for ulcerative colitis.

CYP3A4 Activity is Markedly Lower in Patients with Crohn's Disease

BACKGROUND

Disease-dependent changes in the activity of drug metabolizing enzymes and transporters, such as Cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp), are thought to have a major influence on the disposition of shared substrates. However, little is known regarding the in vivo relevance of these 2 proteins during drug therapy for gastrointestinal diseases. Our aim was to elucidate the activity of CYP3A4 and P-gp in subjects with Crohn's disease (CD) and to evaluate their influence on budesonide pharmacokinetics.

METHODS

A detailed pharmacokinetic assessment was conducted in 8 individuals diagnosed with CD on stable doses of oral budesonide, a putative shared CYP3A4, and P-gp substrate, where hepatic and intestinal CYP3A4 activity were also assessed using intravenous and oral midazolam. In addition, oral fexofenadine was used as an in vivo probe for P-gp activity.

RESULTS

Budesonide area under the curve was highly variable between subjects but similar to previously reported values in healthy subjects. The hepatic and intestinal extraction ratios for midazolam were 0.11 ± 0.06 and 0.64 ± 0.25, respectively; however, CYP3A4 activity was nearly 5-fold lower in our CD cohort compared with published data among healthy subjects. Multivariate regression revealed that only 25% budesonide clearance could be explained based on midazolam or fexofenadine clearance.

CONCLUSIONS

Midazolam and fexofenadine disposition profile did not predict budesonide clearance. However, we observed a marked reduction in vivo CYP3A4 activity among individuals with CD. Therefore, changes in CYP3A4 activity in disease states such as CD may be a heretofore underappreciated determinant of variation in drug responsiveness in CD.

Hydrogel microarray for detection of polymorphisms in the UGT1A1, DPYD, GSTP1 and ABCB1 genes

BACKGROUND

Improving the efficacy of anticancer therapy remains an urgent and very important task. Screening of the individual genetic metabolism of cancer patients allows for prescribing adequate medication in the correct dose as well as for decreasing side effects associated with drug toxicity.

OBJECTIVE

Estimation of a microarray-based method for genotyping of the UGT1A1, DPYD, GSTP1, and ABCB1 metabolic regulation genes to evaluate for an increased risk of toxicity of anticancer drugs.

METHODS

The microarray was used to conduct genotyping of specimens taken from 115 cancer patients and 31 healthy donors.

RESULTS

A microarray-based method for identification of the rs8175347, rs3918290, rs1695, and rs1045642 polymorphisms in the corresponding UGT1A1, DPYD, GSTP1, and ABCB1 genes has been developed for genotyping. The results obtained were in full concordance with those obtained using control sequencing. The frequencies of the rs8175347, rs3918290, rs1695, and rs1045642 genetic variations were 0.38, 0, 0.35, and 0.56, respectively.

CONCLUSION

The implementation of this biochip-based method in diagnostic practice should increase the overall survival and quality of life of cancer patients, decrease the length of their hospital stay, and reduce treatment costs.

Genotypes Affecting the Pharmacokinetics of Anticancer Drugs

Cancer treatment is becoming more and more individually based as a result of the large inter-individual differences that exist in treatment outcome and toxicity when patients are treated using population-based drug doses. Polymorphisms in genes encoding drug-metabolizing enzymes and transporters can significantly influence uptake, metabolism, and elimination of anticancer drugs. As a result, the altered pharmacokinetics can greatly influence drug efficacy and toxicity. Pharmacogenetic screening and/or drug-specific phenotyping of cancer patients eligible for treatment with chemotherapeutic drugs, prior to the start of anticancer treatment, can identify patients with tumors that are likely to be responsive or resistant to the proposed drugs. Similarly, the identification of patients with an increased risk of developing toxicity would allow either dose adaptation or the application of other targeted therapies. This review focuses on the role of genetic polymorphisms significantly altering the pharmacokinetics of anticancer drugs. Polymorphisms in DPYD, TPMT, and UGT1A1 have been described that have a major impact on the pharmacokinetics of 5-fluorouracil, mercaptopurine, and irinotecan, respectively. For other drugs, however, the association of polymorphisms with pharmacokinetics is less clear. To date, the influence of genetic variations on the pharmacokinetics of the increasingly used monoclonal antibodies has hardly been investigated. Some studies indicate that genes encoding the Fcγ-receptor family are of interest, but more research is needed to establish if screening before the start of therapy is beneficial. Considering the profound impact of polymorphisms in drug transporters and drug-metabolizing enzymes on the pharmacokinetics of chemotherapeutic drugs and hence, their toxicity and efficacy, pharmacogenetic and pharmacokinetic profiling should become the standard of care.

ABCB1 polymorphisms and steroid treatment in children with idiopathic nephrotic syndrome

BACKGROUND

The most common cause of nephrotic syndrome (NS) is idiopathic nephrotic syndrome (INS), also called nephrosis. Although most patients respond to steroid therapy, there is unequal response to treatment suggesting the involvement of genetic factors. The current study was conducted to evaluate the influence of two single nucleotide polymorphisms (SNPs) in ABCB1 (C3435T and C1236T) on the steroid treatment response in INS children.

MATERIALS AND METHODS

Genotyping of ABCB1 C3435T and C1236T polymorphisms by real time PCR were conducted on 120 INS children, 80 steroid sensitive (SS) and 40 steroid resistant (SR).

RESULTS

A significant difference in the distribution of ABCB1 C3435T and C1236T genotypes was observed between SS and SR patients. C1236T polymorphism was associated with steroid resistance in INS children (odds ratio: 2.27, 95 % confidence interval: 1.2-4.4; P = 0.012). The frequency of the T allele was significantly higher in SR than in SS patients (81.2 vs. 65.6%, respectively). The odds ratio for the C3435T polymorphism in response to steroid treatment was smaller than that of the polymorphism C1236T, and did not reach statistical significance (odds ratio: 1.1, 95 % confidence interval: 0.6-1.9; P = 0.77).

CONCLUSION

Our results suggested that C1236T polymorphism in ABCB1 gene was associated with steroid resistance. A higher proportion of SR children had C1236T TT genotype and T allele, these patients may require other therapeutic strategies.

Impact of ABCB1 1236C > T-2677G > T-3435C > T polymorphisms on the anti-proliferative activity of imatinib, nilotinib, dasatinib and ponatinib

Overexpression of ABCB1 (also called P-glycoprotein) confers resistance to multiple anticancer drugs, including tyrosine kinase inhibitors (TKIs). Several ABCB1 single nucleotide polymorphisms affect the transporter activity. The most common ABCB1 variants are 1236C > T, 2677G > T, 3435C > T and have been associated with clinical response to imatinib in chronic myelogenous leukaemia (CML) in some studies. We evaluated the impact of these polymorphisms on the anti-proliferative effect and the intracellular accumulation of TKIs (imatinib, nilotinib, dasatinib and ponatinib) in transfected HEK293 and K562 cells. ABCB1 overexpression increased the resistance of cells to doxorubicin, vinblastine and TKIs. Imatinib anti-proliferative effect and accumulation were decreased to a larger extent in cells expressing the ABCB1 wild-type protein compared with the 1236T-2677T-3435T variant relatively to control cells. By contrast, ABCB1 polymorphisms influenced the activity of nilotinib, dasatinib and ponatinib to a much lesser extent. In conclusion, our data suggest that wild-type ABCB1 exports imatinib more efficiently than the 1236T-2677T-3435T variant protein, providing a molecular basis for the reported association between ABCB1 polymorphisms and the response to imatinib in CML. Our results also point to a weaker impact of ABCB1 polymorphisms on the activity of nilotinib, dasatinib and ponatinib.

Relationship between ABCB1 polymorphisms and serum methadone concentration in patients undergoing methadone maintenance therapy (MMT)

BACKGROUND

Methadone is a substrate of the permeability glycoprotein (P-gp) efflux transporter, which is encoded by the ABCB1 (MDR1) gene. Large interindividual variability in serum methadone levels for therapeutic response has been reported. Genetic variations in ABCB1 gene may be responsible for the variability in observed methadone concentrations.

OBJECTIVE

This study investigated the associations of ABCB1 polymorphisms and serum methadone concentration over the 24-hour dosing interval in opioid-dependent patients on methadone maintenance therapy (MMT).

METHODS

One hundred and forty-eight male opioid-dependent patients receiving MMT were recruited. Genomic deoxyribonucleic acid (DNA) was extracted from whole blood and genotyped for ABCB1 polymorphisms [i.e. 1236C>T (dbSNP rs1128503), 2677G>T/A (dbSNP rs2032582), and 3435C>T (dbSNP rs1045642)] using the allelic discrimination real-time polymerase chain reaction (PCR). Blood samples were collected at 0, 0.5, 1, 2, 4, 8, 12, and 24 hours after the dose. Serum methadone concentrations were measured using the Methadone ELISA Kit.

RESULTS

Our results revealed an association of CGC/TTT diplotype (1236C>T, 2677G>T/A, and 3435C>T) with dose-adjusted serum methadone concentration over the 24-hour dosing interval. Patients with CGC/TTT diplotype had 32.9% higher dose-adjusted serum methadone concentration over the 24-hour dosing interval when compared with those without the diplotype [mean (SD) = 8.12 (0.84) and 6.11 (0.41) ng ml^-1 mg^-1, respectively; p = 0.033].

CONCLUSION

There was an association between the CGC/TTT diplotype of ABCB1 polymorphisms and serum methadone concentration over the 24-hour dosing interval among patients on MMT. Genotyping of ABCB1 among opioid-dependent patients on MMT may help individualize and optimize methadone substitution treatment.

Influence of ABCB1 and ABCG2 polymorphisms on the antiemetic efficacy in patients with cancer receiving cisplatin-based chemotherapy: a TRIPLE pharmacogenomics study

Resistance to antiemetic treatment with 5-hydroxytryptamine-3 receptor antagonist is an issue. This study evaluated the potential roles of ABCB1 and ABCG2 polymorphisms in antiemetic treatment resistance in patients with cancer previously enrolled in a randomized controlled trial. A total of 156 patients were evaluated for their responses to antiemetic therapy and then subdivided into granisetron or palonosetron groups. The genotypes were evaluated for their association with antiemetic efficacy in each treatment groups. Additional risk factors associated with complete response (CR) were examined using a multivariate regression analysis. No significant associations were identified for genetic polymorphisms in the palonosetron group. In the granisetron group, patients with ABCB1 2677TT and 3435TT genotypes had higher proportion of CR. In addition to ABCB1 polymorphisms, gender and cisplatin dose were associated with granisetron response by univariate analysis. Multivariate logistic regression analysis revealed that the ABCB1 3435C>T polymorphism and cisplatin dose were significant predictors of CR.

Effects of berberine on pharmacokinetics of midazolam and rhodamine 123 in rats in vivo

Aim

To evaluate whether berberine hydrochloride (BBR) could modify the pharmacokinetic profiles of midazolam (MDZ), a substrate of CYP3A, and rhodamine 123 (Rh123), a substrate of P-glycolprotein (P-gp), in male rats.

Methods

The rats were given with varied does of BBR or 75 mg/kg ketoconazole as a positive control for 10 days by intragastric administration. Single-pass duodenum perfusion of 20 mg/kg MDZ and inguinal artery canulated rats were used in the study. Plasma concentrations of MDZ and 1′-hydroxymidazolam (1′-OH-MDZ) were analyzed by high performance liquid chromatography (HPLC). The rats were given with varied does of BBR or 4 mg/kg verapamil as a positive control for 10 days by intragastric administration. Blood was obtained from the caudal vein of rats after single-pass intragastric administration of 5 mg/kg Rh123. HPLC was used to analyze the plasma concentrations of Rh123.

Results

BBR produced similar results as the ketoconazole (positive control group) with a dose-dependent increase in the AUC_(0−t) and AUMC _(0−t) of midazolam except at the dose of 50 mg/kg (p < 0.01). And BBR could significantly increase the peak plasma concentrations (C_max) of MDZ (p < 0.01), but reduce the clearance rate (CL_z) and the apparent volume of the distribution (V_z) of MDZ (p < 0.05). The results also indicated that BBR had no significant impact on the half-life period (t_1/2) and the time to reach peak concentration (t_max). Meanwhile, BBR could dose-dependently decrease AUC_(0−t) and AUMC_(0−t) of 1′-OH-MDZ significantly (p < 0.05), and expedite the clearance rate of 1′-OH-MDZ while gaining its apparent volume of distribution (p < 0.05), but had no significant impact on t_1/2 and T_max. The result also showed that BBR, except at the dose of 50 mg/kg, and the positive verapamil group could significantly increase the AUC_(0−t) and AUC_(0−∞) of Rh123 (p < 0.001), meanwhile raise C_max of Rh123 and shorten its V_z inversely (p < 0.05). Additionally, pre-treatment with BBR had no significant influence with the half-life period of Rh123, while significantly reduced its clearance rate (p < 0.05).

Conclusion

The metabolism of MDZ and Rh123 was controlled by BBR. The results were most likely due to the inhibition by BBR on CYP3A enzymes and P-gp transporter.

Pharmacogenetics of antiepileptic drugs: A brief review

The goal of pharmacogenetic research is to assist clinicians in predicting patient response to medications when genetic variations are identified. The pharmacogenetic variation of antiepileptic drug response and side effects has yielded findings that have been included in drug labeling and guidelines. The goal of this review is to provide a brief overview of the pharmacogenetic research on antiepileptic drugs. It will focus on findings that have been included in drug labeling, guidelines, and candidate pharmacogenetic variation. Overall, several genes have been included in guidelines by national and international organizations; however, much work is needed to implement and evaluate their use in clinical settings.