The Effect of Uridine Diphosphate Glucuronosyltransferase (UGT)1A6 Genetic Polymorphism on Valproic Acid Pharmacokinetics in Indian Patients with Epilepsy: A Pharmacogenetic Approach

Association of UGT1A6 gene polymorphisms with sodium valproate-induced tremor in patients with epilepsy

BACKGROUND

Individual susceptibility to sodium valproate (VPA)-induced tremors may be due to genetic polymorphisms in the gene encoding the uridine diphosphate glucuronosyltransferase (UGT) enzyme, which affec the drug's clinical efficacy and cause toxic side effects. This study aimed to investigate the association between UGT1A6 polymorphisms and VPA-induced tremors in patients with epilepsy.

METHODS

In total, 128 patients with epilepsy were enrolled. Patients with epilepsy who received VPA were divided into tremor and non-tremor groups. Polymerase chain reaction-restriction fragment length polymorphism was used to investigate the genotype of UGT1A6 polymorphisms.

RESULTS

Carriers of the UGT1A6 A541G mutant genotype conferred a higher risk of tremor than wild-type carriers (odds ratio 2.128, P = 0.045). Logistic regression analysis showed that the A541G mutant genotype was a significant genetic risk factor for VPA-induced tremors. This suggests that individual susceptibility to VPA-induced tremors may result, at least partially, from genetic variation in UGT1A6 A541G.

CONCLUSIONS

Patients with epilepsy carrying the UGT1A6 A541G mutant genotype may have VPA-induced tremors, and early detection of this genotype will help guide the clinical individualizsation of VPA treatment.

Distribution pattern of UGT1A6 and UGT2B7 gene polymorphism and its impact on the pharmacokinetics of valproic acid and carbamazepine: Prospective genetic association study conducted in Pakistani patients with epilepsy

BACKGROUND

Ethnic variation is one of the important factors in clinical practice that may affect the pharmacokinetics of drugs. The present study aims to determine the distribution pattern of UGT1A6 and UGT2B7 gene polymorphism and its possible impact on the metabolism of valproic acid (VPA) and carbamazepine (CBZ) in patients with epilepsy from Khyber Pakhtunkhwa region of Pakistan.

METHODS

After the enrollment of targeted patients, blood was collected for genotype analysis through Sanger sequencing. Plasma concentrations of VPA and CBZ were determined by reversed-phase high-performance liquid chromatography (HPLC) at the follow-up visit of third month from the initiation of therapy. The drug plasma levels were correlated with different genotypes of UGT1A6 and UGT2B7 to determine the impact of genetic polymorphism on the drug metabolism.

RESULTS

Of the total 178 epileptic patients, 120 subjects were prescribed VPA monotherapy while 58 subjects were given CBZ monotherapy. The mean age of the subjects was recorded as 26.1 ± 13.5 years with a predominance of the male gender. Generalized tonic-clonic (GTC) was the most prevalent type of seizure (82%) followed by partial seizure. Genotype analysis revealed that the frequency of homozygous and heterozygous variants of the targeted UGT genes were exceptionally high in the Khyber Pakhtunkhwa population compared to the ethnic groups of other countries. In UGT1A6-A552C and UGT1A6-A541G, AC and AG were the most prevalent genotypes with respective frequencies of 43.2% and 41.1% whereas, in UGT2B7-T161C and UGT2B7-G211T, TC and GG were the most prevalent genotypes with respective frequencies of 42.7% and 99.4%. In the VPA-treated group, the homozygous and heterozygous variants of UGT1A6-A552C and UGT1A6-A541G were significantly associated with lower drug plasma concentrations (p < 0.05). However, none of the genotypes of UGT2B7-T161C revealed any significant association with VPA plasma concentration (p greater than 0.05). In the CBZ-treated group, UGT gene polymorphisms were not recognized to cause alteration in the drug plasma concentrations (p greater than 0.05).

CONCLUSION

The genetic polymorphisms of UGT1A6, but not UGT2B7 significantly affected the plasma levels of valproic acid. The chosen SNPs did not reveal a role in determining the plasma levels of carbamazepine.

Association of ABCB1 Polymorphisms with Efficacy and Adverse Drug Reactions of Valproic Acid in Children with Epilepsy

Genetic polymorphisms in ATP-binding cassette subfamily B member 1 (ABCB1, also known as MDR1) have been reported to be possibly associated with the regulation of response to antiseizure medications. The aim of this study was to investigate the association of ABCB1 polymorphisms with the efficacy of and adverse drug reactions to valproic acid among Chinese children with epilepsy. A total of 170 children from southern China with epilepsy treated with valproic acid for more than one year were recruited, including 61 patients with persistent seizures and 109 patients who were seizure-free. Two single nucleotide polymorphisms of ABCB1, rs1128503 and rs3789243, were genotyped using the Sequenom MassArray system. The two single nucleotide polymorphisms of ABCB1 were found to be significantly associated with treatment outcomes of valproic acid in children with epilepsy. Carriers with the TT genotype of ABCB1 rs1128503 were more inclined to exhibit persistent seizures after treatment with valproic acid (p = 0.013). The CC genotype of rs3789243 was observed to be a potential protective factor for valproic acid-induced gastrointestinal adverse drug reactions (p = 0.018), but possibly increased the risk of valproic acid-induced cutaneous adverse drug reactions (p = 0.011). In contrast, the CT genotype of rs3789243 was associated with a lower risk of valproic acid-induced cutaneous adverse drug reactions (p = 0.011). Haplotype analysis showed that CC haplotype carriers tended to respond better to valproic acid treatment (p = 0.009). Additionally, no significant association was found between ABCB1 polymorphisms and serum concentrations of valproic acid. This study revealed that the polymorphisms and haplotypes of the ABCB1 gene might be associated with the treatment outcomes of valproic acid in Chinese children with epilepsy.

Impact of CYP2C9*2 and *3 polymorphisms on valproate-associated adverse drug reactions in individuals living with epilepsy: a case-control study

Epilepsy is characterized by repeated seizure activity. Valproate, a commonly used antiepileptic drug, shows large inter-individual variation in plasma valproic levels and causes many adverse drug reactions. Aim: To find the influence of CYP2C9*2 and *3 polymorphisms on valproate-associated adverse drug reactions and plasma valproic acid levels in people with epilepsy. Methods: We recruited 158 people with epilepsy (79 cases and 79 controls) from an epilepsy clinic. Steady-state plasma valproic acid levels were measured using liquid chromatography-mass spectrometry and genotyping of CYP2C9 variants was carried out with helps of RT-PCR. Results: The presence of a mutant heterozygous genotype showed an odds ratio (OR) of 2.82 (95% CI: 1.10-7.24) and the adjusted OR was 5.39 (95% CI: 1.69-17.16). There was no significant difference in steady-state plasma valproate concentration between genotypes. Conclusion: The presence of a mutant heterozygous CYP2C9 genotype possesses five-times the risk of developing adverse drug reactions to valproate in people with epilepsy.

Effects of UGT1A, CYP2C9/19 and ABAT polymorphisms on plasma concentration of valproic acid in Chinese epilepsy patients

Aim: To evaluate the association between genetic polymorphisms and plasma concentration-to-dose ratio of valproic acid (CDRV) in Chinese epileptic patients. Methods: A total of 46 epileptic patients treated with valproic acid therapy were enrolled. 18 SNPs in nine genes related to valproic acid were directly sequenced with Sanger methods. Results: Patients carrying UGT1A6 heterozygous genotypes had significantly lower CDRV than those carrying the wild-type genotypes. In contrast, patients with the homozygote genotypes of CYP2C9 and ABAT had higher CDRV than those with the wild-type genotypes and patients with the heterozygous genotypes of CYP2C19 had higher CDRV. Conclusion: Detection of genetic polymorphism in these genes might facilitate an appropriate dose of valproic acid for epileptic patients. Further studies with larger cohorts are necessary to underpin these observations.

Effect of CYP2C19 polymorphisms on serum valproic level acid in Chinese Han patients with schizophrenia

Valproic acid is an anticonvulsant, which is also widely used for treating psychiatric disorders. Some clinical trials have demonstrated benefits of valproic acid augmentation therapy in schizophrenia. Interindividual variability in valproic acid dose and serum concentration may reflect functional consequences of genetic polymorphisms in genes encoding drug-metabolizing enzymes. The aim of this study was to determine the relationship between serum concentrations of valproic acid and single nucleotide polymorphisms of the cytochrome P450 (CYP) 2C19 gene in patients with schizophrenia. All patients had been receiving fixed dose of valproic acid for at least 2 weeks. The daily doses were 0.5–1.5 g. No other drugs except olanzapine were coadministered. Serum concentrations of valproic acid were measured using the ultra-high performance liquid chromatography method with mass-spectrometric detection. The CYP2C19 (CYP2C19*2 G681A rs4244285 and CYP2C19*3 G636A rs4986893) genotypes were identified by real-time PCR analyses. The mean concentration/dose ratios of valproic acid were significantly higher in patients with CYP2C19 *1/*2 genotype (P < 0.01) or CYP2C19 *2/*3 genotype (P < 0.01) than in those with CYP2C12 *1/*1 genotype. The mean concentration/dose ratios of valproic acid were significantly higher in patients with 1 (P < 0.01) or 2 (P < 0.01) mutated alleles for CYP2C19 than in those without mutated alleles. And the post hoc analysis revealed that the result has acceptable statistical (power (1 – β) = 0.8486 at type I  level of 0.05) to support the observed significant associations for CYP2C19 SNPs and serum C/D ratios of valproic acid. The findings of this study suggest that the genetic polymorphisms of CYP2C19 significantly affect the steady-state serum concentrations of valproic acid in Chinese Han population. The determination of the CYP2C19 genotypes may be useful for dosing adjustment in schizophrenia patients on valproic acid therapy.

CYP2C19 & UGT1A6 genetic polymorphisms and the impact on Valproic acid-induced weight gain in people with epilepsy: Prospective genetic association study

OBJECTIVES

To study the association between CYP2C19*2 (681 G > A) and UGT1A6*2 (552A > C) polymorphisms on Valproic acid (VPA)-induced weight gain in People with epilepsy (PWE).

METHODS

We recruited PWE on VPA monotherapy and genotyped for CYP2C19 and UGT1A6 polymorphisms. Association between CYP2C19 polymorphism and weight gain was the primary outcome parameter. We followed them up monthly for six months and recorded Body mass index (BMI), drug compliance, side effects, food frequency, physical activity.

RESULTS

Of 108 participants recruited, we assessed the association between the polymorphism and weight gain in 101 PWE for CYP2C19*2 and 103 PWE for UGT1A6*2 polymorphism. The proportion of participants with weight gain was higher in those with poor and intermediate metabolizer genotypes of CYP2C19 (*1/*2 and *2/*2) compared to extensive metabolizers (*1/*1) [53.3 % vs 31.7 %, RR 1.68, 95 % CI (1.01-2.79), P = 0.03]. However, CYP2C19*2 allele did not show an increased risk of weight gain over the CYP2C19*1 allele. No association could be demonstrated with UGT1A6 genotypes and weight gain. In logistic regression analysis, CYP2C19*2 carrier genotype was the independent predictor of weight gain. OR 2.89 [95% CI (1.07-7.84)]. There were no significant association with serum TSH, fT4, testosterone, and valproate levels with CYP2C19 or UGT1A6 polymorphisms.

SIGNIFICANCE

People with epilepsy carrying CYP2C19 polymorphisms (*1/*2) and (*2/*2) had 3 times higher risk of VPA-induced weight gain compared to wild type (*1/*1).

UGT1A6 and UGT2B7 Gene Polymorphism and its Effect in Pediatric Epileptic Patients on Sodium Valproate Monotherapy

OBJECTIVES

To evaluate the pattern of UGT1A6 and UGT2B7 gene polymorphism in pediatric epileptic patients and to compare the sodium valproate concentration in different patterns of UGT gene polymorphism.

METHODS

In this cross-sectional study, 99 pediatric epileptic patients aged 2-18 y receiving Sodium valproate monotherapy for the past one month were included from JusticeK S Hegde Charitable hospital, Mangalore after obtaining informed consent. Genetic polymorphism patterns were evaluated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Trough level serum valproate concentration was estimated by high-performance liquid chromatography (HPLC). Sodium valproate concentration in different UGT genotypes was compared by Analysis of Variance (ANOVA). P value <0.05 was considered significant.

RESULTS

In the present study population, the predominant mutant allele pattern was observed in UGT1A6 (T19G, A541G, A552C) gene. In UGT2B7 (A268G, C161T) showed predominant mutant allele pattern while (G211T) showed predominant wild type. Mean steady-state sodium valproate concentration was 105.40 ± 49.9 μg/ml and adjusted sodium valproate concentration was 5.5 ± 3.2 mg/kg/L. It was found that there was no statistical difference in sodium valproate concentration in different UGT1A6 and UGT2B7 gene polymorphism.

CONCLUSION

The present study concluded that though there was a difference in pattern of gene polymorphism with concerning UGT1A6 and UGT2B7, however, it has not contributed to variation in serum concentration of sodium valproate in the present study population.

Association of UGT1A6 gene polymorphism with clinical outcome in pediatric epileptic patients on sodium valproate monotherapy

Pediatric epilepsy comprises chronic neurological disorders characterized by recurrent seizures. Sodium valproate is one of the common antiseizure medications used for treatment. Glucuronide conjugation is the major metabolic pathway of sodium valproate, carried out by the enzyme uridine 5'-diphosphate (UDP) glucuronosyl transferase (UGT) whose gene polymorphisms may alter the clinical outcome. The objective of this study was to assess the association between UGT1A6 genetic polymorphism and clinical outcome in terms of efficacy and tolerability in pediatric epileptic patients on sodium valproate monotherapy. Pediatric epileptic patients (n=65) aged 2-18 years receiving sodium valproate monotherapy for the past one month were included. Genetic polymorphism patterns of UGT1A6 (T19G, A541G, A552C) were evaluated by PCR-RFLP. Clinical outcome was seizure control during the 6 months observation period. Tolerability was measured by estimating the hepatic, renal, and other lab parameters. Out of 65 patients, TT (40%), TG (57%), and GG (3%) patterns were observed in UGT1A6 (T19G) gene, AA (51%), AG (40%), and GG (9%) in (A541G) gene, and AA (43%), AC (43%), and CC (14%) in (A552C) gene. No statistical difference in clinical outcome was found for different UGT1A6 genetic polymorphism patterns. We concluded that different patterns of UGT1A6 genetic polymorphism were not associated with the clinical outcome of sodium valproate in terms of efficacy and tolerability. Sodium valproate was well-tolerated among pediatric patients with epilepsy and can be used as an effective antiseizure medication.

Pharmacogenetics of Carbamazepine and Valproate: Focus on Polymorphisms of Drug Metabolizing Enzymes and Transporters

Pharmacogenomics can identify polymorphisms in genes involved in drug pharmacokinetics and pharmacodynamics determining differences in efficacy and safety and causing inter-individual variability in drug response. Therefore, pharmacogenomics can help clinicians in optimizing therapy based on patient's genotype, also in psychiatric and neurological settings. However, pharmacogenetic screenings for psychotropic drugs are not routinely employed in diagnosis and monitoring of patients treated with mood stabilizers, such as carbamazepine and valproate, because their benefit in clinical practice is still controversial. In this review, we summarize the current knowledge on pharmacogenetic biomarkers of these anticonvulsant drugs.

Impact of CYP2C19 and CYP2C9 gene polymorphisms on sodium valproate plasma concentration in patients with epilepsy

BACKGROUND

Valproic acid (VPA) is a broad spectrum anticonvulsant drug, which could be partially metabolised by cytochrome P450 (CYP) 2C9 and 2C19 enzymes. This study was designed to investigate the relationship between CYP2C19 and CYP2C9 gene polymorphisms and the plasma concentrations of VPA in subjects with epilepsy.

METHODS

Eighty-three subjects with epilepsy aged 18-92 years were enrolled in this study. All were treated with sustained-release VPA monotherapy. Based on the genotypes of CYP2C19 and the ability to metabolise substrates, the subjects were divided into poor metabolisers, intermediate metabolisers and extensive metabolisers. Sanger sequencing was used to detect the genotypic and allelic frequencies of CYP2C19 (*1, *2 and *3) and CYP2C9 (*13) of the patients. Automatic immunity analysis was used to find steady-state trough plasma concentrations of VPA. By adjusting the plasma concentrations of VPA with body weight and total daily dose of VPA, the concentration-to-dose ratio of VPA (CDRV) was obtained. Data were analysed using SPSS software.

RESULTS

The genetic frequencies of CYP2C19*2, CYP2C19*3 and CYP2C9*13 were 33.1%, 3.0% and 5.4%, respectively, among patients with epilepsy from Yunnan province, China who used VPA therapy. The CDRV was significantly lower in the CYP2C19 extensive metabolisers (3.33±1.78) than it was in the CYP2C19 intermediate metabolisers (4.45±1.42) and the CYP2C19 poor metabolizers (6.64±1.06). The CYP2C19*2 and CYP2C19*3 alleles were correlated with the plasma VPA concentration, while the CYP2C9*13 allele had no effect on the plasma VPA concentration (p=0.809).

CONCLUSIONS

The genetic polymorphisms of CYP2C19 significantly affect the VPA plasma concentration, and the dosage of VPA for intermediate and poor metabolisers could be lower than for extensive metabolisers. CYP2C9*13 carrier was not closely related to plasma concentrations of VPA in patients with epilepsy.

The Ontogeny of UDP-glucuronosyltransferase Enzymes, Recommendations for Future Profiling Studies and Application Through Physiologically Based Pharmacokinetic Modelling

Limited understanding of drug pharmacokinetics in children is one of the major challenges in paediatric drug development. This is most critical in neonates and infants owing to rapid changes in physiological functions, especially in the activity of drug-metabolising enzymes. Paediatric physiologically based pharmacokinetic models that integrate ontogeny functions for cytochrome P450 enzymes have aided our understanding of drug exposure in children, including those under the age of 2 years. Paediatric physiologically based pharmacokinetic models have consequently been recognised by the European Medicines Agency and the US Food and Drug Administration as innovative tools in paediatric drug development and regulatory decision making. However, little is currently known about age-related changes in UDP-glucuronosyltransferase-mediated metabolism, which represents the most important conjugation reaction for xenobiotics. Therefore, the objective of the review was to conduct a thorough literature survey to summarise our current understanding of age-related changes in UDP-glucuronosyltransferases as well as associated clinical and experimental sources of variance. Our findings indicate that there are distinct differences in UDP-glucuronosyltransferase expression and activity between isoforms for different age groups. In addition, there is substantial variability between individuals and laboratories reported for human liver microsomes, which results in part from a lack of standardised experimental conditions. Therefore, we provide a number of best practice recommendations for experimental conditions, which ultimately may help improve the quality of data used for quantitative clinical pharmacology approaches, and thus for safe and effective pharmacotherapy in children.

Per- and polyfluoroalkyl substances display structure-dependent inhibition towards UDP-glucuronosyltransferases

Per- and polyfluoroalkyl substances (PFASs) are a large group of chemicals and can be detected in environmental and human samples all over the world. Toxicity of existing and emerging PFASs will be a long-term source of concern. This study aimed to investigate structure-dependent inhibitory effects of 14 PFASs towards the activity of 11 UDP-glucuronosyltransferase (UGT) isoforms. In vitro UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was employed to determine the inhibition of PFASs towards different UGT isoforms. All the PFASs showed <75% of inhibition or stimulation effects on UGT1A3, UGT1A7, UGT1A9, UGT2B4, UGT2B7 and UGT2B17. However, PFASs showed broad inhibition on the activity of UGT1A1 and UGT1A8. The activity of UGT1A1 was inhibited by 98.8%, 98%, 79.9%, 77.1%, and 76.9% at 100 μmoL/L of perfluorodecanoic acid (PFDA), perfluorooctanesulfonic acid potassium salt (PFOS), perfluorotetradecanoic acid (PFTA), perfluorooctanoic acid (PFOA) and perfluorododecanoic acid (PFDoA), respectively. UGT1A8 was inhibited by 97.6%, 94.8%, 86.3%, 83.4% and 77.1% by PFDA, PFTA, perfluorooctadecanoic acid (PFOcDA), PFDoA and PFOS, respectively. Additionally, PFDA significantly inhibited UGT1A6 and UGT1A10 by 96.8% and 91.6%, respectively. PFDoA inhibited the activity of UGT2B15 by 88.2%. PFDA and PFOS exhibited competitive inhibition towards UGT1A1, and PFDA and PFTA showed competitive inhibition towards UGT1A8. The inhibition kinetic parameter (K_i) were 3.15, 1.73, 13.15 and 20.21 μmoL/L for PFDA-1A1, PFOS-1A1, PFDA-1A8 and PFTA-1A8, respectively. The values were calculated to be 0.3 μmoL/L and 1.3 μmoL/L for the in vivo inhibition of PFDA towards UGT1A1-and UGT1A8-catalyzed metabolism of substances, and 0.2 μmoL/L and 2.0 μmoL/L for the inhibition of PFOS towards UGT1A1 and the inhibition of PFTA towards UGT1A8, respectively. Molecular docking indicated that hydrogen bonds and hydrophobic interactions contributed to the interaction between PFASs and UGT isoforms. In conclusion, exposure to PFASs might inhibit the activity of UGTs to disturb metabolism of endogenous compounds and xenobiotics. The structure-related effects of PFASs on UGTs would be very important for risk assessment of PFASs.

Interaction between ABCG2 421C>A polymorphism and valproate in their effects on steady-state disposition of lamotrigine in adults with epilepsy

AIMS

To investigate the impact of glucuronidation enzyme (UGT1A4*3 142T>G, UGT1A4*2 70C>A, UGT2B7 -161C>T) and transporter (MDR1/ABCB1 1236C>T, ABCG2 421C>A) polymorphisms on steady-state disposition of lamotrigine and on the lamotrigine-valproate interaction.

METHODS

Adults with epilepsy on lamotrigine monotherapy (n = 131) or lamotrigine + valproate treatment (n = 74) were genotyped and steady-state lamotrigine and valproate morning troughs were determined as a part of routine therapeutic drug monitoring.

RESULTS

No effect of UGT and MDR1/ABCB1 polymorphisms was observed. In the entire cohort, ABCG2 421A allele had no effect however an interaction between the variant allele and valproate was observed: (i) in lamotrigine-only patients, variant allele (vs. wild type homozygosity) was independently (adjustments: age, sex, body mass index, lamotrigine dose, other polymorphisms) associated with mildly lower lamotrigine troughs [geometric means ratio (GMR) = 0.76, 95% confidence interval (CI) 0.59-0.98], whereas in lamotrigine + valproate patients it was associated with higher troughs (GMR = 1.72, 95%CI 1.14-2.62); (ii) valproate cotreatment was overall associated with markedly higher troughs vs. lamotrigine monotherapy (GMR = 3.49, 95%CI 2.73-4.44), but more so in variant allele carriers (GMR = 5.24, 95%CI 3.38-8.15) than in wild type homozygotes (GMR = 2.32, 95%CI 1.89-2.83); (iii) variant allele effects in two treatment subsets and valproate effects in two genotype subsets differed by 2.36-fold (95%CI 1.39-3.67); (iv) increase in lamotrigine troughs associated with increasing valproate troughs was greater in variant allele carriers than in wild type homozygotes, i.e. variant allele effect increased with increasing valproate troughs.

CONCLUSION

This study is first to indicate a potentially relevant interaction between ABCG2 421C>A polymorphism and valproate in their effects on lamotrigine disposition.

Pharmacogenomics in Asia: a systematic review on current trends and novel discoveries

While early pharmacogenomic studies have primarily been carried out in Western populations, there has been a notable increase in the number of Asian studies over the past decade. We systematically reviewed all pharmacogenomic studies conducted in Asia published before 2016 to highlight trends and identify research gaps in Asia. We observed that pharmacogenomic research in Asia was dominated by larger developed countries, notably Japan and Korea, and mainly driven by local researchers. Studies were focused on drugs acting on the CNS, chemotherapeutics and anticoagulants. Significantly, several novel pharmacogenomic associations have emerged from Asian studies. These developments are highly encouraging for the strength of regional scientific and clinical community and propound the importance of discovery studies in different populations.

Association of UGT2B7 and UGT1A4 Polymorphisms with Serum Concentration of Antiepileptic Drugs in Children

Background

This study aimed to analyze the relationship of UGT2B7 and UGT1A4 polymorphisms with metabolism of valproic acid (VPA) and lamotrigine (LTG) in epileptic children.

Material/Methods

We administered VPA (102) and LTG (102) to 204 children with epilepsy. Blood samples were collected before the morning dose. Serum concentration of LTG was measured by high-performance liquid chromatography (HPLC). Serum VPA concentration was tested by fluorescence polarization immunoassay. UGT2B7 A268G, C802T, and G211T polymorphisms, as well as UGT1A4 L48V polymorphism, were assayed by direct automated DNA sequencing after PCR. Evaluation of efficacy was conducted using the Engel method.

Results

The adjusted serum concentration of VPA was 4.26 μg/mL per mg/kg and LTG was 1.56 μg/mL per mg/kg. Multiple linear regression analysis revealed that VPA or LTG adjusted concentration showed a good linear relation with sex and age. UGT2B7 A268G and C802T polymorphisms were demonstrated to affect the serum concentration of VPA (F=3.147, P=0.047; F=22.754, P=0.000). UGT1A4 L48V polymorphism was not related with the serum concentration of LTG (F=5.328, P=0.006). In the efficacy analysis, we found that C802T polymorphism exerted strong effects on efficacy of VPA (χ²=9.265, P=0.010). L48V polymorphism also showed effects on efficacy of LTG (χ²=17.397, P=0.001).

Conclusions

UGT2B7, UGT1A4 polymorphisms play crucial roles in metabolism of VPA and LTG.

UGT1A6- and UGT2B7-related valproic acid pharmacogenomics according to age groups and total drug concentration levels

AIM

The role of UGT1A6 and UGT2B7 polymorphisms and the impact of total drug plasma concentration in valproic acid (VPA) pharmacogenomics.

PATIENTS & METHODS

A total of 134 Greek patients were recruited (76 adults). Patients were genotyped for UGT1A6 19T>G, 541A>G and 552A>C and UGT2B7 802T>C polymorphisms. Patients' demographic and clinical data were registered. Natural logarithm of concentration-to-dose ratio (CDR) was also calculated as the final outcome.

RESULTS

No significant genotype-related differences in VPA metabolism were noted among various subgroups. An increased lnCDR ratio was noted in children patients compared with adults suggesting increased metabolic capability in younger ages.

CONCLUSION

UGT1A6 and UGT2B7 genotypes were not related to significant changes in VPA metabolism, even after controlling for total drug concentration levels. Younger ages were associated with increased VPA clearance rate.

Pharmacogenetics of adverse reactions to antiepileptic drugs

INTRODUCTION

Adverse drug reactions (ADRs) are a major public health concern and a leading cause of morbidity and mortality in the world. In the case of antiepileptic drugs (AEDs), ADRs constitute a barrier to successful treatment since they decrease treatment adherence and impact patients' quality of life of patients. Pharmacogenetics aims to identify genetic polymorphisms associated with drug safety. This article presents a review of genes coding for drug metabolising enzymes and drug transporters, and HLA system genes that have been linked to AED-induced ADRs.

DEVELOPMENT

To date, several genetic variations associated with drug safety have been reported: CYP2C9*2 and *3 alleles, which code for enzymes with decreased activity, have been linked to phenytoin (PHT)-induced neurotoxicity; GSTM1 null alleles with hepatotoxicity induced by carbamazepine (CBZ) and valproic acid (VPA); EPHX1 polymorphisms with teratogenesis; ABCC2 genetic variations with CBZ- and VPA-induced neurological ADRs; and HLA alleles (e.g. HLA-B*15:02, -A*31:01, -B*15:11, -C*08:01) with cutaneous ADRs.

CONCLUSIONS

Published findings show that there are ADRs with a pharmacogenetic basis and a high interethnic variability, which indicates a need for future studies in different populations to gather more useful results for larger number of patients. The search for biomarkers that would allow predicting ADRs to AEDs could improve pharmacotherapy for epilepsy.

Pharmacogenetic insights into migraine treatment in children

Pediatric migraine is a disabling condition that can affect the everyday activities and emotional states of children. Due to the multifactorial character of the pathology and the variety of the disease's phenotypes, establishment of an effective treatment is often challenging. Pharmacological treatment is often administered off-label and includes very different drugs, from analgesics to antidepressants. Since interindividual variability in therapy response commonly causes inefficacy and an exacerbation of symptoms, pharmacogenetics may help to decrease the prescription rate of useless or unsafe drugs. If there are many drugs used in migraine, then there are even more candidate or established pharmacogenetic markers that are implicated in clinical profiles. This article presents the current situation regarding the pharmacogenetics of drugs used in pediatric migraine.