1,721,194 research outputs found
Clinical consequences of cytochrome P4502C9 polymorphisms
No full textThe gene coding for the cytochrome P450 (CYP) enzyme 2C9 (CYP2G9) carries numerous inherited polymorphisms. Those coding for R144C ( 2) and I359L ( 3) amino acid substitutions have both significant functional effects and appreciable high population frequencies, and their in vivo consequences have been studied in humans with regard to drug metabolism. This review summarizes present knowledge about the pharmacokinetics, drug responses, and outcomes of clinical studies in individuals with different CYP2C9 genotypes. Tentative estimates of how CYP2C9 genotyping might be applied to close adjustments in clinical therapy were based on dose-related pharmacokinetic parameters such as clearance or trough drug concentrations. Mean clearances in homozygous carriers of the 3 allele were below 25% of that of the wild type for S-warfarin, tolbutamide, glipizide, celecoxib, and fluvastatin. In the more frequent heterozygous carriers (genotype 1/ 3), the clearances were between 40% and 75%. In these cases in which individual dosages are derived from clinical drug effects, such as for the oral anticoagulants, the pharmacogenetics-based dose adjustments showed a good correlation with the genotype-specific empirically derived doses. In addition to its role in pharmacokinetics, CYP2C9 contributes to the metabolism of fatty, acids, prostanoids. and steroid hormones, and it may catalyze potentially toxic bioactivation reactions. However, our current understanding of the role of CYP2C9 in biotransformation of endogenous signaling molecules and in drug toxicity is relatively meager
Single nucleotide polymorphism characterization by mRNA expression imbalance assessment
No full textThe functional characterization of single nucleotide polymorphism (SNPs) represents a major challenge for pharmacogenetics and related research areas. Here, we propose a procedure, termed mRNA expression imbalance assessment, that can be applied to detect cis-acting SNPs; with an effect on mRNA expression. The procedure is based on the observation that the relative transcript levels derived from the two alleles of an autosomal gene are reflected in the sequence of the amplified cDNA. The key element of the procedure is the detection of a discrepancy between the specific nucleotide signal intensity of a marker SNP in the genomic DNA and in the cDNA. We used the CYP3A5 1/ 3 polymorphism as a proof principle for this approach. In this case, we could even demonstrate that the procedure works equally well with the appropriate tissue samples and in silico, using the existing databanks of sequences. In conclusion, the procedure provides a fast and easy tool, which may facilitate identification of functional SNPs. Pharmacogenetics 14:267-269 (C) 2004 Lippincott Williams Wilkin
Simulation of complex pharmacokinetic models in Microsoft EXCEL
No full textWith the arrival of powerful personal computers in the office numerical methods are accessible to everybody. Simulation of complex processes therefore has become an indispensible tool in research and education. In this paper Microsoft EXCEL is used as a platform for a universal differential equation solver. The software is designed as an add-in aiming at a minimum of required user input to perform a given task. Four examples are included to demonstrate both, the simplicity of use and the versatility of possible applications. While the layout of the program is admittedly geared to the needs of pharmacokineticists, it can be used in any field where sets of differential equations are involved. The software package is available upon request. (C) 2007 Elsevier Ireland Ltd. All rights reserved
On the value of haplotype-based genotype-phenotype analysis and on data transformation in pharmacogenetics and -genomics
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Personalised pharmacogenetics. Evidence-based guidelines and clinical application of pharmacogenetic diagnostics
No full textThe broad clinical application of pharmacogenetic diagnostics for individualised drug treatment is still limited. With the exception of oncological therapies where molecular tumor makers are frequently used to decide upon individual drug therapies, pharmacogenetic testing is not generally offered in clinical laboratory diagnostics, because the costs are not covered by general health insurance and it is not evident what consequences the results of a genotyping test may have for the individual drug treatment. Especially in the context of pharmacokinetics, bioequivalence-based concepts have been developed that allow the individual drug dosage or therapy to be adjusted to genetic polymorphisms in drug metabolism, drug transport that affect drug absorption, metabolism and elimination. Pharmacogenetic aspects are increasingly included in the product information (e.g., on its website the FDA lists more than 60 drug labels that include pharmacogenetic information). However, most pharmacogenetic information on drug labels does not give recommendations for clinical decisions to be made based on individual genotypes. This gap is currently being closed by the development of international consortia aiming to base clinical recommendations on the best available evidence by systematic review of the existing data. The Clinical Pharmacogenetics Implementation Consortium of the Pharmacogenomics Research Network (CPIC) is an international community-driven organisation that is developing peer-reviewed, freely available gene/drug guidelines that are published in full at PharmGKB (http://www.pharmgkb.org). The aim of these guidelines is to give therapeutic recommendations such as dose adjustments or suggestions for the choice of an alternative drug in the case of specific genotypes (phenotypes) that predict slow metabolism or transport of drugs or safety risks or risks of therapeutic failure. These guidelines are not mandatory but serve to facilitate the translation of pharmacogenetic knowledge from bench to bedside
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