Effect of CYB2B6 (c.516G>T), CYP2C9 (c.1075A>C) and UGT1A9 (c.98T>C) polymorphisms on propofol pharmacokinetics in patients submitted to colonoscopy: a cohort study.

BACKGROUND: The aim of this study was to investigate the effect of CYB2B6 (c.516G>T, rs3745274), CYP2C9 (c.1075A>C, rs1057910) and UGT1A9 (c.98T>C, rs72551330) polymorphisms on the pharmacokinetics of single-drug propofol in adult patients undergoing intravenous sedation. METHODS: In this prospective clinical study, a total of 124 patients undergoing anaesthesia with propofol, as a single drug, were evaluated when undergoing colonoscopy procedure. Clinical variables were obtained from the patient's anamnesis prior to performing the anaesthetic procedure, in the moment of the patient's loss of consciousness, during the colonoscopy exam (recorded every 5 min) and in the awakening time. RESULTS: Polymorphic genotypes for the rs3745274 and rs1057910 polymorphisms were associated with bispectral index, target-controlled infusion (TCI)/effector concentration of propofol and TCI/plasma concentration of propofol values. Based on multivariate analysis, it was observed that weight, age, surgery time, systolic blood pressure and the rs1057910 polymorphism corresponded to predictive values for the dose of propofol used. Weight (B = 4.807±0.897), age (B = 1.834±0.834) and duration of surgery (B = 8.164±1.624) corresponded to factors associated with increased propofol dose, while systolic blood pressure (B = -1.892±0.679) and the genotypes (AA vs CA) of the single nucleotide polymorphism (SNP) rs1057910 CYPP2C9 gene (B = -74.161±26.820) decreased the total dose of propofol used. CONCLUSION: We concluded that the rs1057910 and rs3745274 polymorphisms affect the metabolism of propofol in patients exclusively submitted to this drug. Thus, the knowledge of the polymorphic genotypes of the CYPP2C9 and CYB2B6 genes may be predictive of different metabolising phenotypes, suggesting expected behaviours of BIS parameter in the anaesthetic procedure, which contributes to safer monitoring by anaesthesiologists during the clinical intervention.

Population pharmacokinetics of mycophenolic acid in adult kidney transplant patients under prednisone and tacrolimus regimen.

Mycophenolate mofetil (MMF) is typically used in combination with prednisone and tacrolimus to avoid graft rejection in kidney transplant patients. The aim of this study was to develop and validate a population pharmacokinetic model of mycophenolic acid (MPA) in kidney transplant patients to investigate the influence of clinical and genetic covariates and to propose a dosage regimen based on the final model. Adult kidney transplant patients (>18 years old) receiving combination of MMF, prednisone and tacrolimus regimen were included. The population pharmacokinetic model was built using a two-compartment model and First Order Conditional Estimation method with Interaction (FOCEI though NONMEM v.7.4.). A total of 343 MPA concentrations at steady state from 77 kidney transplant patients were included in the analysis. MPA CL/F, V1/F, Q/F, V2/F, and Ka were 12.4 L/h, 45.6 L, 29.9 L/h, 658 L, and 1.67 h-1, respectively. It was found that CL/F increases with serum creatinine and uric acid levels and V1/F is modified by blood urea nitrogen and the UGT1A9 genotype. In the final model the interindividual variabilities associated to CL/F and V1/F were 56.5% and 105.8%, respectively. The residual variability was 41.8%. Evaluation by bootstrapping showed that the final model was stable. The predictive performance was evaluated by goodness-of-fit plots and visual predictive check. Dosage regimens for MMF were proposed based on the final model and would be appropriate for a prospective evaluation. In conclusion, it was built a population pharmacokinetic model for MPA in kidney transplant patients, which include clinical and genetic covariates.

Genetic variants in CYP2A6 and UGT1A9 genes associated with urinary nicotine metabolites in young Mexican smokers.

Nicotine is the major pharmacologically active substance in tobacco. Several studies have examined genotypes related to nicotine metabolism, but few studies have been performed in the Mexican population. The objective was to identify associations between gene variants in metabolizing enzymes and the urinary levels of nicotine metabolites among Mexican smokers. The levels of nicotine and its metabolites were determined in the urine of 88 young smokers from Mexico, and 167 variants in 24 genes associated with nicotine metabolism were genotyped by next-generation sequencing (NGS). Trans-3'-hydroxy-cotinine (3HC) and 4-hydroxy-4-(3-pyridyl)-butanoic acid were the most abundant metabolites (35 and 17%, respectively). CYP2A6*12 was associated with 3HC (p = 0.014). The rs145014075 was associated with creatinine-adjusted levels of nicotine (p = 0.035), while the rs12471326 (UGT1A9) was associated to cotinine-N-glucuronide (p = 0.030). CYP2A6 and UGT1A9 variants are associated to nicotine metabolism. 4HPBA metabolite was an abundant urinary metabolite in young Mexican smokers.

Study on the association of UGT1A9 gene c.98T>C polymorphism and mycophenolic acid plasma levels in renal transplant patients.

Mycophenolate mofetil (MMF) is a prodrug active only after its hydrolysis to mycophenolic acid (MPA). The UGT1A9 enzyme is of special interest since it is the main enzyme involved in the glucuronidation of MPA. Single nucleotide polymorphisms (SNPs) in the UGT1A9 gene may be responsible for individual differences in the pharmacokinetics of MMF. Expression levels and the activity of UGT1A9 may depend on the presence of some SNPs located in the gene promoter region (-2152C>T and -275T>A), as well as changes in the coding region (c.98T>C). The objective of this study was to evaluate the effect of allelic variants of the UGT1A9 c.98T>C polymorphism (rs72551330; g. 87289T>C) on MMF metabolism in renal transplant patients. MPA and MPA 7-O glucuronide (MPAG) levels were determined on plasma samples of kidney transplant patients (N = 39) by high-performance liquid chromatography using ultraviolet detection. DNA was isolated from leukocytes and stored at -20°C. The presence of SNPs was investigated using polymerase chain reaction, followed by amplicon sequencing. The analysis of the UGT1A9 c.98T>C polymorphism revealed that all study patients presented the TT genotype. Diverse MPA and MPAG plasma concentrations were detected, including therapeutic, subtherapeutic, and toxic levels. A standardized molecular method permitted identification of UGT1A9 c.98T>C polymorphism genotypes in the examined renal transplant patients. All individuals of the study group presented the same genotype (c.98TT) for that polymorphism. Thereby, no association between the c.98T>C polymorphism and MPA and MPAG plasma levels could be evaluated, despite different levels of these compounds being observed.

Association of UGT2B7, UGT1A9, ABCG2, and IL23R polymorphisms with rejection risk in kidney transplant patients.

Despite advances in testing compatibility between donor and recipient, graft rejection remains a current concern. Single-nucleotide polymorphisms (SNPs) that codify altered enzymes of metabolism, drug transport, and the immune system may contribute to graft rejection in transplant patients. This study examined the association between SNPs present in genes of these processes and occurrence of graft rejection episodes in 246 kidney transplant patients, 35% of which were diagnosed with rejection. Genotype-gene expression associations were also assessed. Peripheral blood samples were used for genotyping of 24 SNPs on the following genes: CYP3A4, CYP3A5, CYP2E1, POR, UGT2B7, UGT1A9, ABCB1, ABCC2, ABCG2, SLCO1B1, TNF, IL2, IRF5, TGFB1, NFKBIA, IL10, IL23R, NFAT, and CCR5 by real-time PCR. The analysis of gene expression was performed by RT-qPCR. The association between graft rejection episodes and polymorphic variants was assessed using odds ratios. Polymorphisms rs7662029 (UGT2B7) and rs6714486 (UGT1A9) were associated with occurrence of graft rejection episodes, rs7662029 (UGT2B7) exhibited a protective effect (1.85-fold), and rs6714486 (UGT1A9) an increased 1.6-fold increased risk of graft rejection. Among drug transporter genes, only rs2231142 (ABCG2) demonstrated an association with a 1.92-fold decrease in the risk of graft rejection. The immunological SNP rs10889677 (IL23R) was associated with a 1.9-fold enhanced risk of graft rejection. Association between genotypes and gene expression was not detected. Therefore, SNPs of UGT2B7, UGT1A9, ABCG2, and IL23R genes may be useful as candidate markers for screening of risk graft rejection in renal transplant patients. These markers may improve medical decisions, avoiding adverse effects.

Differences in frequencies of UGT1A9, 1A7, and 1A1 genetic polymorphisms in Chinese Tibetan versus Han Chinese populations.

As part of a series of pharmacogenomics studies of the Chinese population, we investigated genetic polymorphisms of some UGT1A regions. The three genes that were analyzed were UGT1A9, 1A7, and 1A1; we sequenced their exons, together with promoters, surrounding introns and 3'-untranslated regions (3'UTR) in 100 unrelated-healthy Chinese Tibetan individuals. We compared the data with information on Han Chinese of the same region, which we downloaded from the HapMap database. We identified 40 polymorphisms; 16 of them were shared by the two populations. We then analyzed their linkage disequilibrium map. The UGT1As cluster can be divided into two linkage blocks in the Tibetan population: Block 1 (UGT1A9, UGT1A7), Block 2 (3'-UTR). Furthermore, we identified haplotypes and selected their tagSNPs. In exon 1 of UGT1A7 gene, 393G>A (Arg131Gln, rs17868324) was found at a frequency of 44.4% in the Tibetan population, compared to only 0.7% in the Han population. The linkage blocks in the Han Chinese sample differed from that of the Chinese Tibetan group; the former had Block 1 (UGT1A9, UGT1A7), Block 2 (UGT1A7), and Block 3 (3'-UTR). These findings provide fundamental information for future molecular genetic studies of the UGT1A gene cluster as well as for personalized medicine in Chinese.

Severe neutropenia in a renal transplant patient suggesting an interaction between mycophenolate and fenofibrate.

OBJECTIVE: To describe a patient in whom initiation of micronized fenofibrate precipitated mycophenolate induced neutropenia. CASE SUMMARY: A 57-year-old man was admitted to the hospital because of febrile neutropenia. He had undergone kidney transplantation seventeen years ago. The patient's immunosuppressive maintenance regimen consisted of mycophenolate mofetil (MMF) 500 mg three times a day, and meprednisone 4 mg daily. His medical history included, hypertension treated with losartan 50mg daily, and dyslipidemia treated with ezetimibe 10mg /simvastatin 20mg for four years (until 2 weeks before admission when micronized fenofibrate 200 mg per day was started because of persistently elevated triglycerides levels. On presentation temperature was 37.8°C and initial laboratory tests showed 3130 White Blood Cell Count(WBC)/µL with neutropenia (absolute neutrophil count (ANC) 313/µL) Fenofibrate and mycophenolate mofetil were discontinued, piperacillin tazobactam 4.5gr three times a day and granulocyte stimulation factor 300 µg/day were started. Three days after admission WBC was 7280/µL, neutrophils: 22%, ANC: 1160/mm(3). Mycophenolate mofetil was restarted and granulocyte stimulation factor was discontinued. One month after discharge his WBC was 4480/µL and ANC 1926/µL. DISCUSSION: The initiation of fenofibrate in a patient on stable and therapeutic doses of mycophenolate may have precipitated mycophenolate induced neutropenia, a well described, dose dependent phenomenon. Mycophenolic acid (MPA) displays a complex pharmacokinetic profile susceptible to potential significant interactions with fenofibrate. Since approximately 99% of MPA and fenofibrate bind to albumin, displacement may occur, leading to increased free MPA. Second competition of fenofibric acid for UGT1A9 an enzyme implicated in conjugation of MPA may have decreased its metabolism. The combination of these two effects may increase the risk of dose dependent neutropenia. Using the Interaction Probability Scale (DIPS), the interaction was designated as probable. CONCLUSIONS: Until further evidence is available, when fenofibrate is started in a renal transplant patient on mycophenolate careful monitoring should be considered to avoid potentially fatal complications.

Pre-transplant mycophenolate mofetil pharmacokinetics in Mexican children.

Mycophenolate mofetil is an immunosuppressive pro-drug frequently used to prevent renal graft rejection. It is hydrolyzed by esterases to obtain the active drug mycophenolic acid (MPA). There is high inter-patient variation in mycophenolic acid pharmacokinetics. Area under the concentration versus time curve (AUC) is used for therapeutic drug monitoring and recommended levels are 30-60 microg x hr/L. The aim of this study was to determine mycophenolic acid pharmacokinetics in children awaiting renal allograft in order to predict mycophenolate mofetil dose requirements. Children with end-stage renal disease on the waiting list for renal allograft transplantation were invited to participate in the study. A nine-point pharmacokinetic profile was performed. All patients received a single dose (600 mg/m2, subcutaneously) of mycophenolate mofetil at time zero. Mycophenolic acid was measured by HPLC. The AUC0-12h was estimated by the trapezoidal rule. Ten children were included in the study. Mean age was 13.5 +/- 3.5 years. The median AUC0-12h was 20.3 microg x hr/L, median Cmax = 0.7 microg/mL. Two children (20%) had no detectable levels of mycophenolic acid after a single mycophenolate mofetil dose, other two patients had AUC > 60 microg x hr/L. One patient had abdominal pain 1 hr after the mycophenolate mofetil dose. Twenty percent of our patients had AUC0-12h higher than the recommended value after a single mycophenolate mofetil dose, those patients should receive lower mycophenolate mofetil dose since the beginning of the transplant to avoid adverse events, and another 20% of patients had no detectable mycophenolic acid levels after a single mycophenolate mofetil dose. UGT1A9 gene polymorphisms remain to be studied in our patients, since they could explain the differences in bioavailability.

Nitroaryl-1,4-dihydropyridines as antioxidants against rat liver microsomes oxidation induced by iron/ascorbate, nitrofurantoin and naphthalene.

1,4-Dihydropyridines (DHPs) used in the treatment of cardiovascular diseases, are calcium channel antagonists and also antioxidant agents. These drugs are metabolized through cytochrome P(450) oxidative system, majority localized in the hepatic endoplasmic reticulum. Several lipophilic drugs generate oxidative stress to be metabolized by this cellular system. Thus, DHP antioxidant properties may prevent the oxidative stress associated with hepatic biotransformation of drugs. In this work, we tested the antioxidant capacity of several synthetic nitro-phenyl-DHPs. These compounds (I-IV) inhibited the microsomal lipid peroxidation, UDPGT oxidative activation and microsomal thiols oxidation; all phenomena induced by Fe(3+)/ascorbate, a generator system of oxygen free radicals. As the same manner, these compounds inhibited the oxygen consumption induced by Cu(2+)/ascorbate in the absence of microsomes. Furthermore, compound III (2,6-dimethyl-4-(4-nitrophenyl)-1,4-dihydropyridin-3,5-ethyl-dicarboxylate) and compound V (N-ethyl-2,6-dimethyl-4-(4-nitrophenyl)-1,4-dihydropyridin-3,5-methyl-dicarboxylate) inhibited the microsomal lipid peroxidation induced by Nitrofurantoin and naphthalene in the presence of NADPH. Oxidative stress induced on endoplasmic reticulum may alter the biotransformation of drugs, so, modifying their plasmatic concentrations and therapeutic effects. When drugs which are activated by biotransformation are administered together with antioxidant drugs, such as DHPs, oxidative stress induced in situ may be prevented.