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Ndadza A, Thomford NE, Mukanganyama S, Wonkam A, Ntsekhe M, Dandara C. The Genetics of Warfarin Dose-Response Variability in Africans: An Expert Perspective on Past, Present, and Future. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2020; 23:152-166. [PMID: 30883300 DOI: 10.1089/omi.2019.0018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Coumarins such as warfarin are prescribed for prevention and treatment of thromboembolic disorders. Warfarin remains the most widely prescribed and an anticoagulant of choice in Africa. Warfarin use is, however, limited by interindividual variability in pharmacokinetics and a narrow therapeutic index. The difference in patients' pharmacodynamic responses to warfarin has been attributed to genetic variation in warfarin metabolism and molecular targets (e.g., CYP2C9 and VKORC1) and host-environment interactions. This expert review offers a synthesis of human genetics studies in Africans with respect to pharmacogenetics-informed warfarin dosing. We identify areas that need future research attention or could benefit from harnessing existing pharmacogenetics knowledge toward rational and optimal therapeutics with warfarin in African patients. A literature search was conducted until January 2019. A total of 343 articles were retrieved from nine African countries: Botswana, Ethiopia, Egypt, Ghana, Kenya, South Africa, Sudan, Tanzania, and Mozambique. We found 19 studies on genetics of warfarin treatment specifically among Africans. Genes examined included CYP2C9, VKORC1, CYP4F2, APOE, CALU, GGCX, and EPHX1. CYP2C9*2 and *3 alleles were highly frequent among Egyptians, while rare in other African populations. CYP2C9*5, *8, *9, and *11, and VKORC1 Asp36Tyr genetic variants explained warfarin variability in Africans better, compared to CYP2C9*2 and *3. In Africa, there is limited pharmacogenetics data on warfarin. Therefore, future research and funding commitments should be prioritized to ensure safe and effective use of warfarin in Africa. Lessons learned in Africa from the science of pharmacogenetics would inform rational therapeutics in hematology, cardiology, and surgical specialties worldwide.
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Affiliation(s)
- Arinao Ndadza
- 1 Pharmacogenomics and Drug Metabolism Research Group, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Nicholas Ekow Thomford
- 1 Pharmacogenomics and Drug Metabolism Research Group, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | | | - Ambroise Wonkam
- 1 Pharmacogenomics and Drug Metabolism Research Group, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Mpiko Ntsekhe
- 3 Division of Cardiology, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Collet Dandara
- 1 Pharmacogenomics and Drug Metabolism Research Group, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Bedewy AML, Sheweita SA, Mostafa MH, Kandil LS. The Influence of CYP2C9 and VKORC1 Gene Polymorphisms on the Response to Warfarin in Egyptians. Indian J Hematol Blood Transfus 2018; 34:328-336. [PMID: 29622878 DOI: 10.1007/s12288-016-0725-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2016] [Accepted: 09/19/2016] [Indexed: 10/20/2022] Open
Abstract
Warfarin is the most commonly used drug for chronic prevention of thromboembolic events, it also ranks high among drugs that cause serious adverse events. The variability in dose requirements has been attributed to inter-individual differences in medical, personal, and genetic factor. Cytochrome P-450 2C9 is the principle enzyme that terminates the anticoagulant effect of warfarin by catalyzing the conversion of the pharmacologically more potent S-enantiomer to its inactive metabolites. Warfarin exerts its effect by inhibition of vitamin K epoxide reductase. This protein is encoded by vitamin K epoxide reductase complex subunit 1 gene (VKORC1). The current study aimed to investigate the pharmacogenetic effect of CYP2C9 and VKORC1 gene polymorphisms on the patients response to warfarin. One hundred cases starting warfarin treatment and 20 healthy controls were enrolled. The mean daily dose of warfarin was calculated from patient's medical records. For each patient, less than 10 % variability in warfarin dose and a target international normalized ratio (INR) within the therapeutic target range were required for at least 3 months for one of the following indications (deep vein thrombosis, pulmonary embolism, cerebrovascular stroke and myocardial infarction) prior to inclusion in the study. Tetraprimer amplification refractory mutation system PCR was performed to determine CYP2C9*2, CYP2C9*3, and the VKORC1 1639 G > A genetic polymorphisms. Plasma warfarin determination was performed using rapid fluorometric assay. Plasma warfarin concentration ranged from 2.19 to 10.98 μg/ml with a median 3.52 μg/ml. Supratherpeutic INR was observed in 11 % of the cases. Thromboembolic complications occurred in 7 % of the cases and 8 % of cases experienced major bleeding. High maintenance dose (>7 mg/day) was associated with the combined non VKORC1*2 and homozygous wild type CYP2C9 (CYP2C9*1*1) alleles, while low maintenance dose was associated with the Variant (AG + AA)/Wild (*1/*1). (p value <0.001). CYP2C9 variant was a risk factor for supratherapeutic INR in the multivariate logistic regression model. Thromboembolic complication and incidence of supratherapeutic INR were observed in patients carrying combined VKORC1 Variant (AG + AA) and CYP2C9 Variant (*2/*3). Data from our study suggest that together with clinical factors, VKORC1 and CYP2C9 polymorphisms are important contributors to warfarin dosing and may help predict adverse effects in Egyptian patients.
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Affiliation(s)
- Ahmed M L Bedewy
- 1Hematology Department, Medical Research Institute, Alexandria University, Alexandria, Egypt.,Abraj Al-Shaker, Zaky Ragab Street, Smouha, Alexandria, 21615 Egypt
| | - Salah A Sheweita
- 2Biotechnology Department, Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt
| | - Mostafa Hasan Mostafa
- 2Biotechnology Department, Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt
| | - Lamia Saeed Kandil
- 3Biochemistry Department, Pharos University in Alexandria, Alexandria, Egypt
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Dagenais R, Wilby KJ, Elewa H, Ensom MHH. Impact of Genetic Polymorphisms on Phenytoin Pharmacokinetics and Clinical Outcomes in the Middle East and North Africa Region. Drugs R D 2017; 17:341-361. [PMID: 28748348 PMCID: PMC5629135 DOI: 10.1007/s40268-017-0195-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Genetic polymorphisms are known to influence outcomes with phenytoin yet effects in the Middle East and North Africa region are poorly understood. OBJECTIVES The objective of this systematic review was to evaluate the impact of genetic polymorphisms on phenytoin pharmacokinetics and clinical outcomes in populations originating from the Middle East and North Africa region, and to characterize genotypic and allelic frequencies within the region for genetic polymorphisms assessed. METHODS MEDLINE (1946-3 May, 2017), EMBASE (1974-3 May, 2017), Pharmacogenomics Knowledge Base, and Public Health Genomics Knowledge Base online databases were searched. Studies were included if genotyping and analyses of phenytoin pharmacokinetics were performed in patients of the Middle East and North Africa region. Study quality was assessed using a National Institutes of Health assessment tool. A secondary search identified studies reporting genotypic and allelic frequencies of assessed genetic polymorphisms within the Middle East and North Africa region. RESULTS Five studies met the inclusion criteria. CYP2C9, CYP2C19, and multidrug resistance protein 1 C3435T variants were evaluated. While CYP2C9*2 and *3 variants significantly reduced phenytoin metabolism, the impacts of CYP2C19*2 and *3 variants were unclear. The multidrug resistance protein 1 CC genotype was associated with drug-resistant epilepsy, but reported impacts on phenytoin pharmacokinetics were conflicting. Appreciable variability in minor allele frequencies existed both between and within countries of the Middle East and North Africa region. CONCLUSIONS CYP2C9 decrease-of-function alleles altered phenytoin pharmacokinetics in patients originating from the Middle East and North Africa region. The impacts of CYP2C19 and multidrug resistance protein 1 C3435T variants on phenytoin pharmacokinetic and clinical outcomes are unclear and require further investigation. Future research should focus on the clinical outcomes associated with phenytoin therapy. PROSPERO 2017: CRD42017057850.
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Affiliation(s)
- Renée Dagenais
- Faculty of Pharmaceutical Sciences, Pharmaceutical Sciences Building, University of British Columbia, Vancouver, BC, Canada
| | - Kyle John Wilby
- College of Pharmacy, Qatar University, PO Box 2713, Doha, Qatar.
| | - Hazem Elewa
- College of Pharmacy, Qatar University, PO Box 2713, Doha, Qatar
| | - Mary H H Ensom
- Faculty of Pharmaceutical Sciences, Pharmaceutical Sciences Building, University of British Columbia, Vancouver, BC, Canada
- Department of Pharmacy, Children's and Women's Health Centre of British Columbia, Vancouver, BC, Canada
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Qayyum A, Najmi MH, Mansoor Q, Irfan M, Naveed AK, Hanif A, Kazmi AR, Ismail M. Frequency of Common VKORC1 Polymorphisms and Their Impact on Warfarin Dose Requirement in Pakistani Population. Clin Appl Thromb Hemost 2016; 24:323-329. [PMID: 27879469 DOI: 10.1177/1076029616680478] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Polymorphisms in vitamin K epoxide reductase complex subunit 1 (VKORC1) gene lead to interindividual variability in warfarin dose requirement. The characterization of genotype frequency distribution is required in different populations for construction of customized dosing algorithms to enhance the efficacy and reduce the toxicity of warfarin therapy. This study was carried out in Pakistani population to evaluate the contribution of common VKORC1 polymorphisms to warfarin therapy. A total of 550 stable patients taking warfarin were enrolled after medical history, physical examination, and laboratory investigations. Single blood sample was collected after informed consent. Genomic DNA was extracted and genotype analysis for VKORC1 1173C>T and VKORC1-1639G>A polymorphisms was done by polymerase chain reaction-restriction fragment length polymorphism assay. A number of samples were also analyzed by direct DNA sequencing for validation of results. Data were analyzed using SPSS version 20. Genotype frequency distributions of VKORC1 1173C>T and VKORC1-1639G>A were found to be different from other populations. Both of these polymorphisms did not demonstrate significant effect on warfarin dose requirement. Although Cytochrome P450 2C9 (CYP2C9) and VKORC1 polymorphisms together attributed only 3.8% variability in warfarin dose but it was statistically significant ( p value = .004). It is concluded that there is a need to study genotype frequency distribution and their effect on warfarin dose variability among different populations due to diversity in outcome. At the same time, no effect on warfarin dose variation explained by VKORC1 polymorphisms and small variability explained by studied genotypes stresses the need for exploration of more genetic and nongenetic factors in Pakistani population.
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Affiliation(s)
- Aisha Qayyum
- 1 Department of Pharmacology, Fazaia Medical College, Air University, Islamabad, Pakistan
| | - Muzammil Hasan Najmi
- 2 Department of Pharmacology, Foundation University Medical College, Islamabad, Pakistan
| | - Qaisar Mansoor
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
| | - Muhammad Irfan
- 4 Department of Zoology, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan
| | - Abdul Khaliq Naveed
- 5 Department of Biochemistry, Islamic International Medical College, Riphah International University, Rawalpindi, Pakistan
| | - Andleeb Hanif
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
| | - Ali Raza Kazmi
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
| | - Muhammad Ismail
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
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Qayyum A, Najmi MH, Mansoor Q, Farooqi ZUR, Naveed AK, Hanif A, Kazmi SAR, Ismail M. Frequency of Common CYP2C9 Polymorphisms and Their Impact on Warfarin Dose Requirement in Pakistani Population. Clin Appl Thromb Hemost 2016; 23:800-806. [PMID: 27313202 DOI: 10.1177/1076029616654264] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Polymorphisms in cytochrome P450 (CYP) 2C9 (CYP2C9) gene result in interindividual variability in warfarin dose requirement. There is a need for characterization of genotype frequency distribution in different populations for construction of customized dosing algorithms to enhance the efficacy and reduce the toxicity of warfarin therapy. This study was carried out in Pakistani population to evaluate the contribution of common CYP2C9 polymorphisms to warfarin therapy. A total of 550 stable patients taking warfarin were enrolled after medical history, physical examination, and laboratory investigations. Single blood sample was collected after informed consent. Genomic DNA was extracted, and genotype analysis for CYP2C9*2 and CYP2C9*3 polymorphisms was done by polymerase chain reaction-restriction fragment length polymorphism assay. A number of samples were also analyzed by direct DNA sequencing for validation of the results. Data were analyzed using SPSS version 20. Genotype frequency distribution of CYP2C9*2 and CYP2C9*3 was found to be different from other populations. Of these 2 polymorphisms, CYP2C9*2 did not demonstrate significant effect on warfarin dose requirement, whereas CYP2C9*3 did show significant effect ( P value = .012). It is concluded that there is a need to study genotype frequency distribution and their effect on warfarin dose variability among different populations due to diversity in outcome.
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Affiliation(s)
- Aisha Qayyum
- 1 Department of Pharmacology, Fazaia Medical College, Air University, Islamabad, Pakistan
| | - Muzammil Hasan Najmi
- 2 Department of Pharmacology, Foundation University Medical College, Islamabad, Pakistan
| | - Qaisar Mansoor
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
| | - Zia-Ur-Rehman Farooqi
- 4 Department of Medical Technology, ShifaTameer-e-Millat University, Islamabad, Pakistan
| | - Abdul Khaliq Naveed
- 5 Department of Biochemistry, Islamic International Medical College, Riphah International University, Rawalpindi, Pakistan
| | - Andleeb Hanif
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
| | | | - Muhammad Ismail
- 3 Institute of Biomedical and Genetic Engineering, Islamabad, Pakistan
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Alrashid MH, Al-Serri A, Alshemmari SH, Koshi P, Al-Bustan SA. Association of Genetic Polymorphisms in the VKORC1 and CYP2C9 Genes with Warfarin Dosage in a Group of Kuwaiti Individuals. Mol Diagn Ther 2016; 20:183-90. [DOI: 10.1007/s40291-016-0190-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ding Y, He P, He N, Li Q, Sun J, Yao J, Yi S, Xu H, Wu D, Wang X, Jin T. Genetic polymorphisms of pharmacogenomic VIP variants in Li nationality of southern China. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2016; 42:237-242. [PMID: 26901752 DOI: 10.1016/j.etap.2016.02.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/29/2016] [Accepted: 02/02/2016] [Indexed: 06/05/2023]
Abstract
OBJECTIVES The present study aimed to screen members of the Li nationality in southern China for genotype frequencies of VIP variants and to determine differences between the Li ethnicity and global human population samples in HapMap. METHODS In this study, we genotyped 77 very important pharmacogenetic (VIP) variants selected from the pharmacogenomics knowledge base (PharmGKB) in members of the Li population and compared our data with other eleven populations from the HapMap data set. RESULTS Our results showed that VDR rs1540339, VKORC1 rs9934438, and MTHFR rs1801133 were most different in Li compared with most of the eleven populations from the HapMap data set. Furthermore, population structure and F-statistics (Fst) analysis also showed differences between the Li and other HapMap populations, and the results suggest that the Li are most genetically similar to the CHD population, and the least similar to the YRI in HapMap. CONCLUSIONS The findings of our study complement the pharmacogenomics database with information on members of the Li ethnicity and provide a stronger scientific basis for safer drug administration, which may help clinicians to predict individual drug responses, thereby avoiding the risk of adverse effects and optimizing efficacy in this population.
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Affiliation(s)
- Yipeng Ding
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China.
| | - Ping He
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Na He
- School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, China; National Engineering Research Center for Miniaturized Detection Systems, Xi'an 710069, China
| | - Quanni Li
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Juan Sun
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Jinjian Yao
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Shengyang Yi
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Heping Xu
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Duoyi Wu
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Xiang Wang
- Department of Emergency, People's Hospital of Hainan Province, Haikou, Hainan 570311, China
| | - Tianbo Jin
- School of Medicine, Xizang Minzu University, Xianyang, Shaanxi 712082, China; National Engineering Research Center for Miniaturized Detection Systems, Xi'an 710069, China; School of Life Sciences, Northwest University, Xi'an, Shaanxi 710069, China.
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Yan X, Yang F, Zhou H, Zhang H, Liu J, Ma K, Li Y, Zhu J, Ding J. Effects of VKORC1 Genetic Polymorphisms on Warfarin Maintenance Dose Requirement in a Chinese Han Population. Med Sci Monit 2015; 21:3577-84. [PMID: 26583785 PMCID: PMC4657763 DOI: 10.12659/msm.894414] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background VKORC1 is reported to be capable of treating several diseases with thrombotic risk, such as cardiac valve replacement. Some single-nucleotide polymorphisms (SNPs) in VKORC1 are documented to be associated with clinical differences in warfarin maintenance dose. This study explored the correlations of VKORC1–1639 G/A, 1173 C/T and 497 T/G genetic polymorphisms with warfarin maintenance dose requirement in patients undergoing cardiac valve replacement. Material/Methods A total of 298 patients undergoing cardiac valve replacement were recruited. During follow-up, clinical data were recorded. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was applied to detect VKORC1–1639 G/A, 1173 C/T and 497 T/G polymorphisms, and genotypes were analyzed. Results Correlations between warfarin maintenance dose and baseline characteristics revealed statistical significances of age, gender and operation methods with warfarin maintenance dose (all P<0.05). Warfarin maintenance dose in VKORC1–1639 G/A AG + GG carriers was obviously higher than in AA carriers (P<0.001). As compared with patients with TT genotype in VKORC1 1173 C/T, warfarin maintenance dose was apparently higher in patients with CT genotype (P<0.001). Linear regression analysis revealed that gender, operation method, method for heart valve replacement, as well as VKORC1–1639 G/A and 1173 C/T gene polymorphisms were significantly related to warfarin maintenance dose (all P<0.05). Conclusions VKORC1 gene polymorphisms are key genetic factors to affect individual differences in warfarin maintenance dose in patients undergoing cardiac valve replacement; meanwhile, gender, operation method and method for heart valve replacement might also be correlate with warfarin maintenance dose.
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Affiliation(s)
- Xiaojuan Yan
- Department of Respiratory Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei College of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Feng Yang
- Department of Cardiovascular Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei College of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Hanyun Zhou
- Department of Cardiovascular Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei College of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Hongshen Zhang
- Department of Cardiovascular Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei College of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Jianfei Liu
- Department of Cardiovascular Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei College of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Kezhong Ma
- Department of Cardiovascular Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei College of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Yi Li
- Department of Pharmacy, Ministry of Health Beijing Hospital, Beijing, China (mainland)
| | - Jun Zhu
- Medical Department, Henan Provincial Corps Hospital of Chinese People's Armed Police Force, Zhengzhou, Henan, China (mainland)
| | - Jianqiang Ding
- Medical Department, Henan Provincial Corps Hospital of Chinese People's Armed Police Force, Zhengzhou, Henan, China (mainland)
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Kamal El-Din MA, Farhan MS, El Shiha RI, El-Kaffas RMH, Mousa SM. Frequency of CYP2C9 and VKORC1 gene polymorphisms and their influence on warfarin dose in Egyptian pediatric patients. Paediatr Drugs 2014; 16:337-41. [PMID: 24797541 DOI: 10.1007/s40272-014-0073-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
INTRODUCTION Warfarin is a widely used anticoagulant that shows a high inter-individual variability in the dose needed to achieve target anticoagulation. In adults, common genetic variants in the cytochrome P450-2C9 (CYP2C9) and vitamin K epoxide reductase complex (VKORC1) enzymes, in addition to non-genetic factors, explain this dose variability. In children, data about warfarin pharmacogenetics are limited and inconsistent. METHODS CYP2C9 (*2 and *3) alleles and the VKORC1 (C1173T and G-1639A) polymorphisms were studied by multiplex real time polymerase chain reaction in 41 pediatric patients who received stable warfarin maintenance dose. RESULTS The allele frequency of the studied genes was CYP2C9*2 (0.085), CYP2C9*3 (0.12), VKORC1 1173T (0.52), and VKORC1 -1639A (0.54). In univariate analysis, patients' age, weight, and height were significantly (p < 0.0001) associated with warfarin maintenance dose. However, CYP2C9 and VKORC1 gene polymorphisms did not affect warfarin dose. In multivariate analysis, age was found to be the only significant determinant of daily warfarin maintenance dose (p = 0.045). CONCLUSION Age was the most significant determinant of warfarin dosage in this preliminary study including Egyptian pediatric patients. Further studies involving larger numbers of children are warranted to determine the true impact of genetic factors on warfarin doses in pediatric patients.
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Affiliation(s)
- Mennat-Allah Kamal El-Din
- Clinical Pathology Department, Kasr Al-Ainy School of Medicine, Cairo University, P.O. Box 99, Manial El-Roda, Cairo, 11553, Egypt
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Anderson SL, Marrs JC. Probable Interaction Between Warfarin and Divalproex Sodium. J Pharm Technol 2014; 30:8-12. [DOI: 10.1177/8755122513514379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Objective: A potential interaction between warfarin and divalproex sodium is described. Case Summary: A 65-year-old Arabic-speaking Egyptian woman chronically anticoagulated with warfarin for atrial fibrillation and a history of stroke presented to the anticoagulation clinic with an elevated international normalized ratio (INR) of 3.2. This was an increase of 1.4 over her previous INR of 1.8 only 9 days prior. Discussion with the patient’s daughter revealed the addition of divalproex sodium (a derivative of valproic acid) 250 mg twice daily to the patient’s medication regimen 6 days prior. Other contributing factors that could cause an elevated INR were ruled out. The patient’s total weekly dose (TWD) of warfarin was decreased from 22.5 mg to 20 mg, and the patient was instructed to return for a repeat INR in 1 week. On the day the patient was due to return for a repeat INR, she was admitted to the hospital and her INR was 2.2 on admission. Based on medication reconciliation information, the patient had decreased her warfarin TWD as instructed and had self-discontinued the divalproex sodium due to intolerable fatigue. During this time, the patient received no additional divalproex sodium. She was instructed to resume her previous TWD of warfarin of 22.5 mg on discharge and subsequently had a therapeutic INR (2.6) 11 days later. Discussion: Warfarin and divalproex sodium are commonly prescribed agents with few case reports to describe their interaction. Primary literature supports a multifactorial mechanism, including CYP450 metabolism inhibition and protein-binding displacement, both of which can result in an elevated INR. Use of the Drug Interaction Probability Scale indicated a probable interaction between warfarin and divalproex sodium. Conclusions: Patients receiving concurrent warfarin and divalproex sodium therapy should be monitored closely for changes in INR values as the combination may increase the INR and put the patient at increased risk for bleeding.
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Affiliation(s)
- Sarah L. Anderson
- University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, Aurora, CO, USA
- Denver Health Medical Center, Denver, CO, USA
| | - Joel C. Marrs
- University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, Aurora, CO, USA
- Denver Health Medical Center, Denver, CO, USA
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Kumar DK, Shewade DG, Manjunath S, Ushakiran P, Reneega G, Adithan C. Inter and intra ethnic variation of vitamin K epoxide reductase complex and cytochrome P450 4F2 genetic polymorphisms and their prevalence in South Indian population. INDIAN JOURNAL OF HUMAN GENETICS 2013; 19:301-10. [PMID: 24339542 PMCID: PMC3841554 DOI: 10.4103/0971-6866.120817] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND: Genetic variation in the vitamin K epoxide reductase complex (VKORC1) and cytochrome P450 4F2 (CYP4F2) genes were found to be strongly associated with the oral anticoagulant (OA) dose requirement. The distribution of genetic variation in these two genes was found to show large inter- and intra-ethnic difference. MATERIALS AND METHODS: A total of 470 unrelated, healthy volunteers of South Indians of either sex (age: 18-60 years) were enrolled for the study. A 5 ml of venous blood was collected and the genomic deoxyribonucleic acid (DNA) was extracted by using phenol-chloroform extraction method. Real-time quantitative polymerase chain reaction (RT-PCR) method was used for genotyping. RESULTS: The variant allele frequencies of VKORC1 rs2359612 (T), rs8050894 (C), rs9934438 (T) and rs9923231 (A) were found to be 11.0%, 11.8%, 11.7% and 12.0%, respectively. The variant allele VKORC1 rs7294 was (80.1%) more frequent and the variant allele CYP4F2 * 3 was found to be 41.8% in South Indians. The allele, genotype and haplotype frequencies of VKORC1 and CYP4F2 gene were distinct from other compared HapMap populations (P < 0.0001). CONCLUSION: The findings of our study provide the basic genetic information for further pharmacogenetic based investigation of OA therapy in the population.
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Affiliation(s)
- Dhakchinamoorthi Krishna Kumar
- Department of Pharmacology, Indian Council of Medical Research Centre for Advance Research in Pharmacogenomics, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
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Validation of a Proposed Warfarin Dosing Algorithm Based on the Genetic Make-Up of Egyptian Patients. Mol Diagn Ther 2013; 17:381-90. [DOI: 10.1007/s40291-013-0046-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Bazan NS, Sabry NA, Rizk A, Mokhtar S, Badary OA. Factors affecting warfarin dose requirements and quality of anticoagulation in adult Egyptian patients: role of gene polymorphism. Ir J Med Sci 2013; 183:161-72. [DOI: 10.1007/s11845-013-0978-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 06/11/2013] [Indexed: 12/22/2022]
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Fung E, Patsopoulos NA, Belknap SM, O'Rourke DJ, Robb JF, Anderson JL, Shworak NW, Moore JH. Effect of genetic variants, especially CYP2C9 and VKORC1, on the pharmacology of warfarin. Semin Thromb Hemost 2012; 38:893-904. [PMID: 23041981 DOI: 10.1055/s-0032-1328891] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The genes encoding the cytochrome P450 2C9 enzyme (CYP2C9) and vitamin K-epoxide reductase complex unit 1 (VKORC1) are major determinants of anticoagulant response to warfarin. Together with patient demographics and clinical information, they account for approximately one-half of the warfarin dose variance in individuals of European descent. Recent prospective and randomized controlled trial data support pharmacogenetic guidance with their use in warfarin dose initiation and titration. Benefits from pharmacogenetics-guided warfarin dosing have been reported to extend beyond the period of initial dosing, with supportive data indicating benefits to at least 3 months. The genetic effects of VKORC1 and CYP2C9 in African and Asian populations are concordant with those in individuals of European ancestry; however, frequency distribution of allelic variants can vary considerably between major populations. Future randomized controlled trials in multiethnic settings using population-specific dosing algorithms will allow us to further ascertain the generalizability and cost-effectiveness of pharmacogenetics-guided warfarin therapy. Additional genome-wide association studies may help us to improve and refine dosing algorithms and potentially identify novel biological pathways.
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Affiliation(s)
- Erik Fung
- Section of Cardiology, Heart & Vascular Center, Lebanon, New Hampshire 03756, USA.
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