Presence Of CYP2C9 Research Articles

Effects of pharmacogenetic profiles on pediatric pain relief and adverse events with ibuprofen and oxycodone.

Individual genetic variation may influence clinical effects for pain medications. Effects of CYP2C9, CYP3A4, and CYP2D6 polymorphisms on clinical effectiveness and safety for ibuprofen and oxycodone were studied. Primary objectives were to AU2 evaluate if allelic variations would affect clinical effectiveness and adverse events (AEs) occurrence. This pragmatic prospective, observational cohort included children aged 4 to 16 years who were seen in a pediatric emergency department with an acute fracture and prescribed ibuprofen or oxycodone for at-home pain management. Saliva samples were obtained for genotyping of allelic variants, and daily telephone follow-up was conducted for 3 days. Pain was measured using the Faces Pain Scale-Revised. We included 210 children (n = 140 ibuprofen and n = 70 oxycodone); mean age was 11.1 (±SD 3.5) years, 33.8% were female. Median pain reduction on day 1 was similar between groups [ibuprofen 4 (IQR 2,4) and oxycodone 4 (IQR 2,6), P = 0.69]. Over the 3 days, the oxycodone group experienced more AE than the ibuprofen group (78.3% vs 53.2%, P < 0.001). Those with a CYP2C9*2 reduced function allele experienced less adverse events with ibuprofen compared with those with a normal functioning allele CYP2C9*1 (P = 0.003). Neither CYP3A4 variants nor CYP2D6 phenotype classification affected clinical effect or AE. Although pain relief was similar, children receiving oxycodone experienced more AE, overall, than those receiving ibuprofen. For children receiving ibuprofen or oxycodone, pain relief was not affected by genetic variations in CYP2C9 or CYP3A4/CYP2D6, respectively. For children receiving ibuprofen, the presence of CYP2C9*2 was associated with less adverse events.

Impact of genetic and non-genetic factors on hepatic CYP2C9 expression and activity in Hungarian subjects

CYP2C9, one of the most abundant hepatic cytochrome P450 enzymes, is involved in metabolism of 15–20% of clinically important drugs (warfarin, sulfonylureas, phenytoin, non-steroid anti-inflammatory drugs). To avoid adverse events and/or impaired drug-response, CYP2C9 pharmacogenetic testing is recommended. The impact of CYP2C9 polymorphic alleles (CYP2C9*2, CYP2C9*3) and phenoconverting non-genetic factors on CYP2C9 function and expression was investigated in liver tissues from Caucasian subjects (N = 164). The presence of CYP2C9*3 allele was associated with CYP2C9 functional impairment, and CYP2C9*2 influenced tolbutamide 4′-hydroxylase activity only in subjects with two polymorphic alleles, whereas the contribution of CYP2C8*3 was not confirmed. In addition to CYP2C9 genetic polymorphisms, non-genetic factors (co-medication with CYP2C9-specific inhibitors/inducers and non-specific factors including amoxicillin + clavulanic acid therapy or chronic alcohol consumption) contributed to the prediction of hepatic CYP2C9 activity; however, a CYP2C9 genotype–phenotype mismatch still existed in 32.6% of the subjects. Substantial variability in CYP2C9 mRNA levels, irrespective of CYP2C9 genotype, was demonstrated; however, CYP2C9 induction and non-specific non-genetic factors potentially resulting in liver injury appeared to modify CYP2C9 expression. In conclusion, complex implementation of CYP2C9 genotype and non-genetic factors for the most accurate estimation of hepatic CYP2C9 activity may improve efficiency and safety of medication with CYP2C9 substrate drugs in clinical practice.

The Effect of Polymorphisms in the CYP2D6 and CYP2C9 Genes on the Clinical Efficacy of Tramadol and Ketorolac When Using the Accelerated Recovery Protocol in Patients With Uncomplicated Acute Calculous Cholecystitis Who Underwent Cholecystectomy

Relevance. One of the key components of the accelerated recovery protocols (ARP), in addition to minimizing the surgical approach, is an adequate postoperative analgesia. Despite this, applied postoperative analgesia combinations are not devoid of drawbacks, such as lack of effective postoperative analgesia and the presence of side effect. The use of a pharmacogenetic approach to analgesic therapy for the purpose of its personalization may increase the effectiveness and safety of the use of analgesics. In particular, the presence of an inactive CYP2D6*4 allele , in which the conversion of tramadol to its active metabolite is reduced, contributes to the insufficient efficacy of the drug. As for non-steroidal anti-inflammatory drugs, the presence of CYP2C9*2/*3 polymorphisms leads to a decrease in drug metabolism and a longer half-life, resulting in the increase of the clinical effect and the risk of adverse reactions. Thus, genotyping of patients with the determination of the presence of specific genetic factors can rationalize the postoperative analgesia.Aim of study. Evaluation of the possible association of polymorphisms of the CYP2D6 and CYP2C9 genes with the clinical efficacy of tramadol and ketorolac in relation to postoperative pain.Material and methods. This observational clinical study involved 107 patients with uncomplicated acute calculous cholecystitis who underwent videolaparoscopic cholecystectomy and perioperative treatment according to ARP. All patients underwent whole blood sampling followed by real-time polymerase chain reaction genotyping. Analgesic efficacy was assessed using a visual analog scale (VAS) and McGill Pain Questionnaire.Results. In CYP2D64* carriers pain was higher than that of wild-type carriers, according to VAS and McGill Pain Questionnaire in all investigated periods. In carriers of CYP2C9*2, the pain syndrome was lower than in carriers of the wild type at all intervals studied. In carriers of CYP2C9*3 pain was lower only after 2 and 6 hours, also according to McGill Pain Questionnaire.Conclusion. 1. The presence of the polymorphic marker CYP2D6*4 may reduce the efficacy of postoperative tramadol analgesia compared with wild type. 2. The presence of the polymorphic marker CYP2C9*2 and CYP2C9*3 may increase the efficacy of ketorolac pain relief compared to wild type.

Algorithm for the Choice of Anticoagulant for Patients with Atrial Fibrillation

Aim. To evaluate the effectiveness of the anticoagulant choice algorithm in the prevention of complications of atrial fibrillation (AF). Material and methods. Patients with AF (n=98) were included into observational prospective study. The level of adherence to treatment, risk of food interactions and presence of CYP2C9 and VKORC1 genes mutations were determined at the initial examination. These indicators were necessary to specify an eligible anticoagulant according to the evaluated algorithm. Therapy was prescribed by the attending physician. Hemorrhagic and thromboembolic complications were assessed at the next examination after 24 weeks. Results. Hemorrhagic complications were observed in 31.6% of patients during the follow-up. Their number was comparable in individuals taking antiplatelet agents and direct oral anticoagulants (DOACs) (χ2=1.44; p&lt;0.49, Pearson) and significantly more in individuals taking warfarin (as compared to DOACs: χ2=25.08; p&lt;0.000, Pearson; and antiplatelet agents: χ2=34.32; p&lt;0.000, Pearson). Thromboembolic complications were reported in 8.16% of patients. Their number was more in patients taking DOACs than warfarin (χ2=7.03; p&lt;0.03, Pearson). Patients who had to take DOACs according to the algorithm, but in the study took warfarin, demonstrated significantly greater number of thromboembolic complications, with a comparable number of hemorrhagic complications. Patients who could take warfarin according to the algorithm, but in the study took DOACs, had significantly greater number of thromboembolic complications, with a comparable number of hemorrhagic complications. Conclusion. The results of the study demonstrated the potential for reduction in complications, especially thromboembolic, in the choice of anticoagulant using the algorithm; and reduction in complications of therapy, primarily with warfarin, due to the initial prescription of DOACs. The proposed approach, which consists in using the quantitative assessment of adherence to treatment, and only if necessary supplemented by the assessment of food preferences and/or pharmacogenetic studies, contributes to the treatment optimization.

Identification of environmental and genetic factors that influence warfarin time in therapeutic range.

Warfarin is an oral anticoagulant prescribed to prevent and treat thromboembolic disorders. It has a narrow therapeutic window and must have its effect controlled. Prothrombin test, expressed in INR value, is used for dose management. Time in therapeutic range (TTR) is an important outcome of quality control of anticoagulation therapy and is influenced by several factors. The aim of this study was to identify genetic, demographic, and clinical factors that can potentially influence TTR. In total,422 patients using warfarin were investigated. Glibenclamide co-medication and presence of CYP2C9*2 and/or *3 alleles were associated with higher TTR, while amiodarone, acetaminophen and verapamil co-medication were associated with lower TTR. Our data suggest that TTR is influenced by co-medication and genetic factors. Thus, individuals in use of glibenclamide may need a more careful monitoring and genetic testing (CYP2C9*2 and/or *3 alleles) may improve the anticoagulation management. In addition, in order to reach and maintain the INR in the target for a longer period, it is better to discuss dose adjustment in office instead of by telephone assessment. Other studies are needed to confirm these results and to find more variables that could contribute to this important parameter.

CYP2C9 polymorphisms are associated with phenytoin toxicity in South-Indian epileptic patients

Background and Aims: The contribution of CYP2C9 in phenytoin metabolism is generally modest, but it increases with increasing serum phenytoin concentration. In the current study, we sought to study the association of CYP2C9*2 and CYP2C9*3 polymorphism with clinical and biochemical phenytoin toxicity in epileptic patients presenting to a tertiary care hospital in South-India. Methods: In total, 50 patients on phenytoin therapy and clinically diagnosed with phenytoin toxicity in neurology outpatient department/casualty/intensive care unit and medicine wards were considered as cases. A total of 50 patients on phenytoin therapy without any evidence of toxicity were considered as controls. CYP2C9*2 (exon-3) and CYP2C9*3 (exon-7) gene polymorphisms were studied using the allele specific PCR method. Results: Out of 100 patients, CYP2C9*2 polymorphism was seen in 8 (8%) patients in which 6 (12%) were cases and 2 (4%) were controls. CYP2C9*3 polymorphism was seen in 23 (23%) patients out of which 17 (34%) were cases and 6 (12%) were controls. Mean serum phenytoin level in cases was 24.23 ± 1.3 μg/ml, whereas in controls, it was 17.10 ± 0.6 μg/ml and the difference was statistically significant with P value Conclusion: Our findings conclude that the presence of CYP2C9*2 and CYP2C9*3 polymorphisms are associated with increased serum phenytoin levels and increased risk of clinical toxicity with phenytoin.

Possibilities of optimizing approaches to the treatment of resistant epilepsy in children using pharmacogenetic studies data

We conducted an observation of 83 children with therapy-resistant forms of epilepsy between the ages of 11 months and 18 years. The presence of CYP2C9, CYP2C19 and CYP3A4 gene polymorphisms was detected in 60 of the examined patients, that is, 72.29 % of them, 33 patients (39.76 %) had CYP2C19 gene polymorphisms, CYP2C9 gene polymorphisms had 17 (20.48 %) children, and 10 (12.05 %) of them had CYP3A4 gene polymorphisms. The frequency of CYP2C19*2 and CYP3A4*1B polymorphisms was signifi cantly higher than in the Ukrainian and other European populations, no statistical data signifi - cance of differences in the frequency of CYP2C9 gene polymorphisms compared with the Ukrainian population was found. CYP2C19 gene polymorphisms are signifi cantly more frequently recorded by us compared to the results obtained by researchers in Russia and Turkey in closely related studies. It is shown that children with cytochrome P450 gene polymorphisms are recommended: more frequent clinical, instrumental, and laboratory monitoring of patients to prevent side eff ects of therapy; monitoring (not a one-time study) of AED concentration in blood plasma. The necessity of conduction of pharmacogenetic research at the stage of debut of epilepsy in the case of suspicion of treatment-resistant form of the disease and in the case of ineffi - ciency or severe side eff ects of the fi rst assigned AED was demonstrated. Key words: children, treatment, resistant epilepsy, cytochrome P450, gene polymorphism.

Влияние цитофлавина на апоптоз лейкоцитов крови пациентов с ишемической болезнью сердца в зависимости от носительства полиморфизма гена цитохрома CYP2C9 в условиях &lt;i&gt;in vitro&lt;/i&gt;

С целью определения характера влияния цитофлавина на апоптоз лейкоцитов крови пациентов с ишемической болезнью сердца (ИБС) в зависимости от наличия полиморфизма гена цитохрома CYP2C9*2 C430T были обследованы 90 пациентов с ИБС: стабильной стенокардией напряжения. Методом полимеразной цепной реакции определяли генные полиморфизмы цитохрома CYP2C9*2 C430T. Методом ДНК-комет, который позволяет оценить уровень апоптоза белых клеток крови, по разработанному авторами способу в тестах in vitro оценивали влияние цитофлавина в терапевтической концентрации на ДНК лейкоцитов крови больных. При частотном анализе гена CYP2C9*2 C430T среди пациентов было установлено, что 75 человек (83 %) гомозиготны по дикому аллелю (генотип СС), 15 человек (17 %) — гетерозиготны (генотип СТ), гомозиготных лиц по полиморфному аллелю (генотип ТТ) в выборке не обнаружено. У носителей полиморфного гена цитохрома CYP2C9*2 С430Т (генотипа СТ) наблюдали более сильное повреждение ДНК в исходном статусе (11,00 ± 3,21) % повреждённых клеток в сравнении с (3,43 ± 1,13) % у пациентов с генотипом СС (р = 0,02). При введении цитофлавина в терапевтической концентрации in vitro обнаружили тенденцию разнонаправленного изменения состояния ДНК лейкоцитов в зависимости от наличия полиморфизма гена CYP2C9*2 С430Т. Так, у пациентов с диким геном CYP2C9*2 С430Т при введении цитофлавина in vitro обнаружили незначительное недостоверное увеличение количества апоптотических лейкоцитов крови, в то время как у пациентов с полиморфным геном CYP2C9*2 С430Т (генотипом СТ) обнаружили чёткую тенденцию снижения количества апоптотических клеток практически до нулевых значений показателя (p = 0,087), что позволяет выдвинуть гипотезу о возможной способности цитофлавина модулировать стабильность ДНК в зависимости от состояния генома и о необходимости разработки персонализированных подходов к использованию цитофлавина у пациентов с ИБС в клинической практике.

CYP2C9 and OATP1B1 genetic polymorphisms affect the metabolism and transport of glimepiride and gliclazide

The therapeutic use of glimepiride and gliclazide shows substantial inter-individual variation in pharmacokinetics and pharmacodynamics in human populations, which might be caused by genetic differences among individuals. The aim of this study was to assess the effect of CYP2C9 and OATP1B1 genetic polymorphisms on the metabolism and transport of glimepiride and gliclazide. The uptake of glimepiride and gliclazide was measured in OATP1B1*1a, *5 and *15-HEK293T cells, and their metabolism was measured using CYP2C9*1, *2 and *3 recombinase by LC-MS. Glimepiride in OATP1B1*1a, *5 and *15-HEK293T cells had Vmax values of 155 ± 18.7, 80 ± 9.6, and 84.5 ± 8.2 pmol/min/mg, while gliclazide had Vmax values of 15.7 ± 4.6, 7.2 ± 2.5, and 8.7 ± 2.4 pmol/min/mg, respectively. The clearance of glimepiride and gliclazide in OATP1B1*5 and *15 was significantly reduced compared to the wild-type. Glimepiride in the presence of CYP2C9*1, *2 and *3 recombinase had Vmax values of 21.58 ± 7.78, 15.69 ± 5.59, and 9.17 ± 3.03 nmol/min/mg protein, while gliclazide had Vmax values of 15.73 ± 3.11, 10.53 ± 4.06, and 6.21 ± 2.94 nmol/min/mg protein, respectively. The clearance of glimepiride and gliclazide in CYP2C9*2 and *3 was significantly reduced compared to the wild-type. These findings collectively indicate that OATP1B1*5 and *15 and CYP2C9*2 and *3 have a significant effect on the transport and metabolism of glimepiride and gliclazide.

The effect of CYP2C9*2, CYP2C9*3, and VKORC1-1639 G>A polymorphism in patients under warfarin therapy in city of Kermanshah.

Polymorphism in the genes encoding CYP2C9 enzyme and VKORC1 reductase significantly influence warfarin dose requirement since patients with CYP2C9*2, CYP2C9*3 and VKORC1 mutant alleles require lower warfarin maintenance doses. Studies have reported the ethnic variations in the frequency of these genes within the various populations in Iran and other parts of the world. However, no such study has been done yet on Kurdish population in Kermanshah. From Kurdish population of Kermanshah province in Iran, a total of 110 patients who had heart surgery and taking warfarin, were genotyped for polymorphisms of VKORC1-1639 G>A, CYP2C9*2, and CYP2C9*3. Polymorphism genotyping was performed by sequencing as well as polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using restriction enzymes of MspI, AVAII and KpnI, respectively. The frequencies of VKORC1-1639 GG, GA, and AA genotypes were 42%, 36%, and 22%, respectively and for CYP2C9 1*/1*, 1*/2*, 2*/2*, 1*/3*, 3*/3*, 2*/3* were 71%, 17%, 5.4%, 1.8%, 4.5%, and 0%, respectively. The frequency of VKORC1-1639A allele was 42.3% and the frequencies of CYP2C9*2 and *3 alleles were 14% and 5.4%, respectively. It was indicated that low warfarin dose requirements are strongly associated with the presence of CYP2C9 and VKORC1-1639 variant alleles. Our results confirmed the supply to understand the distribution of genomic biomarkers related to the drugs metabolism for future planning health programs.

Predictors of warfarin dose requirements in South African patients attending an anticoagulation clinic

Warfarin is the most common oral anticoagulant for the treatment and prevention of thromboembolic disease. However, it has a wide interpatient variability in dose requirements due to various genetic and clinical factors. This study investigated the effect of clinical and genetic factors on the variability of warfarin dose requirements in 147 South African patients (81 white and 66 black). The study was performed at a University Hospital Anticoagulation Clinic managed by nursing sisters at the Charlotte Maxeke Johannesburg Academic Hospital. The most common indication for anticoagulation was atrial fibrillation (n=55, 37.4%). The mean warfarin dose was significantly higher in black patients as compared to white patients (5.4±2.9mg/day and 3.8±2.1mg/day, respectively; P<0.001). Older age was significantly associated with a lower maintenance warfarin dose (P<0.001). Drugs which decreased the international normalized ratio (INR) were significantly associated with a higher maintenance warfarin dose of 6.4±3.4mg/day (P<0.034). In contrast, there was no significant difference in warfarin dosage requirements in the presence of CYP2C9 and VKORC1 variant alleles (P>0.05). Patients, however, homozygous for CYP2C9 *1,*3, and VKORC1 required less than 5mg/day of warfarin to maintain the INR within the therapeutic range. In conclusion, this study indicates that clinical characteristics including; age, ethnic group, and drugs which decrease the INR might help to predict better dose requirements in this population group and thereby reduce the risk of bleeding and thrombotic complications.

Investigating the Role of Plasma Glucose Concentration as a Phenotypic Marker for CYP2C9 Genetic Variants, in the Diabetic Population of Gujarat.

The present study was aimed to investigate the role of plasma glucose concentration as a phenotypic marker and to study the frequency distribution of CYP2C9 genetic variants in Gujarat state diabetic population. One hundred and nine unrelated diabetes mellitus patients treated with sulfonylureas were genotyped for CYP2C9*2 and CYP2C9*3 alleles. Their pre- and posttreatment postprandial blood glucose levels were recorded and mean glucose drop per milligram of drug values were calculated and further used as an index for phenotypic correlation. The frequencies of CYP2C9*1, CYP2C9*2 and CYP2C9*3 alleles in the Gujarat state diabetic population were 0.84, 0.07 and 0.09, respectively. The distribution of CYP2C9*1/*1, CYP2C9*1/*2, CYP2C9*1/*3, CYP2C9*2/*2, CYP2C9*2/*3 and CYP2C9*3/*3 genotypes were 0.73, 0.08, 0.13, 0.0, 0.06 and 0.0, respectively. Patients with CYP2C9*1/*2 genotype did not show any significant difference in the mean glucose drop per milligram of drug values when compared with wild-type patients in glipizide-treatment group. Patients with CYP2C9*1/*3 genotype showed greater mean glucose drop per milligram of drug values than patients with CYP2C9*1/*1 wild-type genotype for both glipizide and glimepiride while patients with CYP2C9*2/*3 genotype showed greater drop than patients with CYP2C9*1/*1 genotype only in the glipizide-treatment group. The presence of CYP2C9*3 allele significantly affected plasma glucose drop per milligram of drug values in patients taking glipizide and glimepiride, while effects of CYP2C9*2 allele were insignificant. Further studies are needed to confirm the effects of CYP2C9*2 allele on plasma glucose drop per milligram of drug values. However, plasma glucose concentration is a complex physiological marker that cannot be used to establish perfect genotype-phenotype correlation. Hence studies exploring robust phenotypic markers must be initiated.

A New Pharmacogenetic Algorithm to Predict the Most Appropriate Dosage of Acenocoumarol for Stable Anticoagulation in a Mixed Spanish Population

There is a strong association between genetic polymorphisms and the acenocoumarol dosage requirements. Genotyping the polymorphisms involved in the pharmacokinetics and pharmacodynamics of acenocoumarol before starting anticoagulant therapy would result in a better quality of life and a more efficient use of healthcare resources. The objective of this study is to develop a new algorithm that includes clinical and genetic variables to predict the most appropriate acenocoumarol dosage for stable anticoagulation in a wide range of patients. We recruited 685 patients from 2 Spanish hospitals and 1 primary healthcare center. We randomly chose 80% of the patients (n = 556), considering an equitable distribution of genotypes to form the generation cohort. The remaining 20% (n = 129) formed the validation cohort. Multiple linear regression was used to generate the algorithm using the acenocoumarol stable dosage as the dependent variable and the clinical and genotypic variables as the independent variables. The variables included in the algorithm were age, weight, amiodarone use, enzyme inducer status, international normalized ratio target range and the presence of CYP2C9*2 (rs1799853), CYP2C9*3 (rs1057910), VKORC1 (rs9923231) and CYP4F2 (rs2108622). The coefficient of determination (R2) explained by the algorithm was 52.8% in the generation cohort and 64% in the validation cohort. The following R2 values were evaluated by pathology: atrial fibrillation, 57.4%; valve replacement, 56.3%; and venous thromboembolic disease, 51.5%. When the patients were classified into 3 dosage groups according to the stable dosage (<11 mg/week, 11–21 mg/week, >21 mg/week), the percentage of correctly classified patients was higher in the intermediate group, whereas differences between pharmacogenetic and clinical algorithms increased in the extreme dosage groups. Our algorithm could improve acenocoumarol dosage selection for patients who will begin treatment with this drug, especially in extreme-dosage patients. The predictability of the pharmacogenetic algorithm did not vary significantly between diseases.

High prevalence of VKORC1*3 (G9041A) genetic polymorphism in north Indians: A study on patients with cardiac disorders on acenocoumarol.

Coumarin derivatives such as warfarin and acenocoumarol are used in various disorders such as deep venous thrombosis, pulmonary embolism, atrial fibrillation and artificial heart valves. They have improved prognosis of patients with thromboembolic disease. An individual's response to coumarins depends on several factors. The non-genetic factors include age, gender, body mass index, diet and interacting drugs. Among the genetic factors, the cytochrome P450 system and vitamin K epoxide reductase complex subunit 1 play a key role in drug metabolism. This was a prospective hospital based study in which allele and genotypic frequencies of CYP2C9 gene polymorphisms; 430C>T and 1075A>C and VKORC1 gene polymorphisms; 1639G>A, 9041G>A and 6009C>T in 106 alleles of north Indian patients with valve replacement on acenocoumarol were determined and their effect on acenocoumarol dosing was studied. To the best of our knowledge, this is first report of VKORC1 9041G>A and 6009C>T gene polymorphisms and their effect on acenocoumarol dosing from north India. In 53 patients with valve replacement on acenocoumarol with stable INR, the allele frequency of CYP2C9*2 and CYP2C9*3 gene polymorphisms was 0.05 and 0.17 respectively and that of VKORC1 *2,*3 and *4 gene polymorphisms was 0.15, 0.72 and 0.11 respectively. The presence of CYP2C9*3 or VKORC1*2 gene polymorphism were associated with decrease in acenocoumarol dose requirements (p values 0.03 and 0.02 respectively).This study confirmed the association of lower mean weekly dosages of acenocoumarol in patients with CYP2C9*3 and VKORC1*2 gene polymorphisms. An unusually high frequency of 9041A polymorphism in VKORC1 was found in study population.

A New Algorithm for Weekly Phenprocoumon Dose Variation in a Southern Brazilian Population: Role for CYP2C9, CYP3A4/5 and VKORC1 Genes Polymorphisms

Phenprocoumon is widely used in prophylaxis and treatment of thromboembolic disorders. However, its pharmacokinetics and pharmacodynamics vary according to several genetic and non-genetic factors. Phenprocoumon metabolism is mediated by CYP2C9 and CYP3A enzymes. Moreover, VKORC1 is phenprocoumon target of action. Therefore, the aim of this study was to evaluate the association of single nucleotide polymorphisms (SNPs) in VKORC1, CYP2C9, CYP3A4 and CYP3A5 genes with the variance of weekly phenprocoumon dose as well as to develop an algorithm for dose prediction based on genetic and environmental factors. A total of 198 patients with stable phenprocoumon dose, 81% of European ancestry, were investigated. Genotypes were determined by allelic discrimination with TaqMan assays. Polymorphisms -1639G>A and 1173C>T in VKORC1 and the presence of CYP2C9*2 and/or CYP2C9*3 are associated with lower doses. On the other hand, 3730G>A in VKORC1 gene is associated with higher doses. No association was found between CYP3A4*1B, CYP3A5*3 and CYP3A5*6 polymorphisms. Among non-genetic factors, gender, height, age and use of captopril, omeprazole, simvastatin and β-blockers are associated with dose. Two algorithms were derived: one for the whole sample explained 42% of dose variation and one for patients of European ancestry only which explained 46% of phenprocoumon dose. The mean absolute difference between observed and predicted dose was low in both models (3.92mg/week and 3.54mg/week, for models 1 and 2, respectively). However, more studies with other genes and environmental factors are needed to test and to improve the algorithm.

The contribution of human small intestine to chlorpyrifos biotransformation

Despite the oral intake is the major route of exposure to chlorpyrifos for the general population, few data are available on human intestine biotransformation. In this study the contribution of chlorpyrifos (CPF) metabolism in human small intestine was investigated in microsomes from duodenum (HDM) and ileum/jejunum (HS2M) from 11 individual donors. Samples were characterized for testosterone hydroxylated metabolite formation and CYP content quantification by means of Western blotting. The two methods gave consistent results, evidencing the presence of CY3A4 and its-related activity in 10/11 samples, among which one showed also the presence of CYP2C9. Analogously, although with high interindividual variability (about 10 fold), CPF bioactivation to chlorpyrifos-oxon (CPFO) was observed in 10/11 HDM: intrinsic clearance highest value was 0.75pmolCPFO/(mgproteinminμM). Detoxication to 3,5,6-trichloropyrin-2-ol formation was negligible. The comparison between HDM and HS2M indicates that most CPF bioactivation was confined in the duodenum, declining toward the distal ileum. Results suggest that following oral exposure, the small intestine CPF bioactivation, although much lower when compared to the total hepatic metabolism, could play a role in the pre-systemic CPF clearance, with CPFO transported into the lumen by the efflux P-glycoprotein and further metabolized by esterases.

CYP2C9 and VKORC1 Gene Polymorphism is Inessential for Bleeding Development under Conditions of Oral Application of Anticoagulant Acenocoumarol in Russian Patients at High Risk of Thromboembolic Complications

The study included 52 patients at a high risk of thromboembolic complications, with permanent atrial fibrillation. All patients were treated with acenocoumarol for 6 months and the incidence of hemorrhages was evaluated in all of them. All patients were genotyped by CYP2C9 and VKORC1. The presence of CYP2C9*2 and CYP2C9*3 alleles of CYP2C9 locus and AA genotype of VCORC1 gene polymorphic G-1639(3673)A marker was not associated with the development of hemorrhages under conditions of acenocoumarol treatment (p=0.144 for CYP2C9, p=0.809 and 0.918 for VCORC1 in the total group and subgroup of patients with CYP2C9*1/*1 genotype, respectively). The search for other genetic markers of acenocoumarol efficiency and safety is needed for predicting the risk of hemorrhages during this treatment.

Influence of CYP2C9 genetic variants on gastrointestinal bleeding associated with nonsteroidal anti-inflammatory drugs

The existence of genetic polymorphisms in metabolizing enzymes can be regarded as one of the principal causes of interindividual variation in response to drugs and adverse reactions. In the case of enzyme CYP2C9, the presence of genetic coding variants could be considered a risk factor for suffering from gastrointestinal haemorrhages associated with the use of nonsteroidal anti-inflammatory drugs, due to a reduction in the enzyme's rate of metabolism. The aim of this study was to conduct a systematic critical review aimed at assessing whether the presence of CYP2C9*2 and CYP2C9*3 could increase the risk of suffering from gastrointestinal haemorrhages due to nonsteroidal anti-inflammatory drug use. Using MEDLINE as the data source, the search was limited to scientific studies published in English. Six studies met the inclusion criteria, whereas three reported no results because there were no homozygous mutant genotypes for CYP2C9*2 and *3 in their samples, risk of bleeding was associated by one with the presence of CYP2C9*2 and by two with the CYP2C9*3 coding variant. Some of the studies included in this review contained methodological limitations, which prevented the increased risk of suffering gastrointestinal haemorrhages due to nonsteroidal anti-inflammatory drug use from being satisfactorily linked to the presence of CYP2C9 coding variants.

Presence of CYP2C9*3 Allele Increases Risk for Hypoglycemia in Type 2 Diabetic Patients Treated with Sulfonylureas

Hypoglycemia is a common adverse effect of sulfonylurea oral hypoglycemic agents. Impaired metabolism of sulfonylureas due to gene polymorphisms in the metabolic enzyme CYP2C9 might lead to hypoglycemia. In the present study we explored the association of the CYP2C9 variant alleles CYP2C9*2 and CYP2C9*3 with the incidence of hypoglycemic events in diabetic patients receiving the sulfonylureas glimepiride and gliclazide. A total of 92 Type 2 diabetes mellitus (T2DM) patients receiving sulfonylurea and reporting drug-associated hypoglycemia, and 84 T2DM patients receiving sulfonylurea and having never experienced hypoglycemia were included in the study. A sample of 283 nondiabetic controls that had been genotyped earlier served as a second control group. CYP2C9*2 and *3 alleles were detected by use of PCR-RFLP analysis. Frequencies of CYP2C9*1/*3 genotype and CYP2C9*3 allele were significantly lower in T2DM patients than nondiabetic controls (p = 0.003 and p = 0.017, respectively). A total of 11 out of 92 subjects (12%) experiencing hypoglycemia carried the CYP2C9*3 allele, as opposed to only 1 out of 84 subjects (1.2%) free of sulfonylurea-induced hypoglycemia. In a model adjusted for age, BMI, mean daily dose of sulfonylurea, duration of T2DM and renal function, CYP2C9*1/*3 genotype increased the hypoglycemia risk in response to sulfonylurea (odds ratio: 1.687; p = 0.011). However, no differences in CYP2C9*2 allele frequency between the two groups were found. The presence of CYP2C9*3 appears to be protective for development of T2DM. Furthermore, in T2DM patients, CYP2C9*3 increases the risk of hypoglycemia when they are treated with sulfonylureas, possibly due to impaired metabolism of these drugs. CYP2C9 genotyping might thus be a useful tool for predicting adverse effects caused by sulfonylureas and help clinicians in safer prescribing of oral hypoglycemic agents. The potential T2DM protective effect of CYP2C9*3 allele requires further investigation.

Influence of clinical and genetic factors on warfarin dose requirements among Japanese patients

The aim of this study was to investigate the influence of clinical and genetic factors on warfarin dose requirements in the Japanese population. We enrolled 125 patients on stable warfarin anticoagulant therapy with an international normalized ratio maintained between 1.5 and 3.0. PCR-based methods were performed to analyze genetic polymorphisms in the genes pharmacokinetically and pharmacodynamically related to warfarin reactions, including cytochrome P450 (CYP) 2C9, vitamin K epoxide reductase complex subunit 1 (VKORC1), gamma-glutamyl carboxylase (GGCX) and factor VII (FVII). The presence of CYP2C9*3 and VKORC1-1639G>A had a significant impact on the mean maintenance dose of warfarin (CYP2C9*1/*1 2.74 +/- 1.24 mg/day vs. *1/*3 and *3/*3 1.56 +/- 0.85 mg/day, P = 0.009; VKORC1-1639AA 2.42 +/- 0.95 mg/day vs. GA 3.71 +/- 1.43 mg/day vs. GG 7.25 +/- 0.35 mg/day, P < 0.001). In the multiple linear regression model, the combination of age, body surface area, and genotypes of CYP2C9*3 and VKORC1-1639G>A explained 54.8% of the variance in warfarin dose requirements. The influences of CYP2C9*3 and VKORC1-1639G>A on the maintenance dose of warfarin were well-defined in Japanese patients, while polymorphisms of GGCX and FVII did not affect it. The model established in this study might provide us most likely individual maintenance dose based on clinical and genetic backgrounds.