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Genetic polymorphisms and drug interactions leading to clopidogrel resistance: why the Asian population requires special attention

Hasan MS, Basri HB, Hin LP, Stanslas J

Int J Neurosci, 2013 Mar;123(3):143-54.
PMID: 23110469 DOI: 10.3109/00207454.2012.744308

Ischemic heart disease and stroke are the two leading causes of death worldwide. Antiplatelet therapy plays the most significant role in the management of these cardiovascular and cerebrovascular occlusive events to prevent recurrent ischemic attack. Clopidogrel, an antiplatelet drug, is widely prescribed either alone or in combination with aspirin as dual antiplatelet therapy for the prevention of vascular occlusive events. The antiplatelet response to clopidogrel varies widely. Hyporesponders and nonresponders are likely to have adverse cardiovascular events during follow-up. Some drugs, such as proton pump inhibitors (omeprazole), calcium channel blockers, selective serotonin reuptake inhibitors (nefazadone), coumarin derivatives (phenprocoumon), benzodiazepines, sulfonylurea, erythromycin, and itraconazole, decrease the antiplatelet effect of clopidogrel when administered concomitantly. Decreased response to clopidogrel is common among Asians due to genetic polymorphisms associated with clopidogrel resistance, and it is nearly 70% in some of the Asian communities. It is necessary to study Asian populations, because there are a large number of Asians throughout the world due to increased migration. Current guidelines do not make genetic testing or platelet response testing mandatory prior to clopidogrel prescription. Therefore, it is important for clinicians treating Asian patients to keep in mind the interindividual variability in response to clopidogrel when prescribing the drug.

Matched MeSH terms: Ticlopidine/pharmacology
The effect of CYP2C19 genetic polymorphism and non-genetic factors on clopidogrel platelets inhibition in East Asian coronary artery disease patients

Amin AM, Sheau Chin L, Mohamed Noor DA, Mostafa H, Abdul Kader MASK, Kah Hay Y, et al.

Thromb Res, 2017 10;158:22-24.
PMID: 28802144 DOI: 10.1016/j.thromres.2017.07.032
Matched MeSH terms: Ticlopidine/pharmacology
CYP2C19 genotypes and their impact on clopidogrel responsiveness in percutaneous coronary intervention

Mejin M, Tiong WN, Lai LY, Tiong LL, Bujang AM, Hwang SS, et al.

Int J Clin Pharm, 2013 Aug;35(4):621-8.
PMID: 23661171 DOI: 10.1007/s11096-013-9783-y

BACKGROUND: Cytochrome P450 2C19 (CYP2C19) loss-of-function polymorphisms are more common in Asian populations and have been associated with diminished antiplatelet response to clopidogrel. In this era of 'personalised medicine', combining genotyping and phenotyping as a strategy to personalise antiplatelet therapy warrants further exploration.
OBJECTIVE: This study aimed to investigate the prevalence and impact of CYP2C19*2, *3 and *17 genotypes on clopidogrel responsiveness in a multiethnic Malaysian population planned for percutaneous coronary intervention.
SETTING: Between October 2010 and March 2011, a total of 118 consecutive patients planned for percutaneous coronary intervention were enrolled in Sarawak General Hospital, Borneo. All patients received at least 75 mg aspirin daily for at least 2 days and 75 mg clopidogrel daily for at least 4 days prior to angiography.
METHOD: Genotyping for CYP2C19*2 (rs4244285, 681G > A), *3 (rs4986893, 636G > A) and *17 (rs11188072, -3402C > T) alleles were performed by polymerase chain reaction-restriction fragment linked polymorphism method. Whole blood ADP-induced platelet aggregation was assessed with multiple electrode platelet aggregometry (MEA) using the Multiplate Analyzer.
MAIN OUTCOME MEASURES: The distribution of CYP2C19*2, *3 and *17 among different ethnic groups and the association between genotype, clopidogrel responsiveness and clinical outcome were the main outcome measures.
RESULTS: The highest prevalence of poor metabolisers (carriers of at least one copy of the *2 or *3 allele) was among the Chinese (53.7 %), followed by the Malays (26.9 %), Ibans (16.4 %) and other races (3.0 %). Poor metabolisers (PMs) had the highest mean MEA (303.6 AU*min), followed by normal metabolisers (NMs) with 270.5 AU*min and extensive metabolisers (EMs) with 264.1 AU*min (p = 0.518). Among poor responders to clopidogrel, 65.2 % were PMs and NMs, respectively, whereas none were EMs (p = 0.350). Two cardiac-related deaths were reported.
CONCLUSION: There was a diverse inter-ethnic difference in the distribution of CYP2C19 polymorphism. The findings of this study echo that of other studies where genotype appears to have a limited impact on clopidogrel responsiveness and clinical outcome in low-risk patients.

Matched MeSH terms: Ticlopidine/pharmacology
CYP2C19 and PON1 polymorphisms regulating clopidogrel bioactivation in Chinese, Malay and Indian subjects

Chan MY, Tan K, Tan HC, Huan PT, Li B, Phua QH, et al.

Pharmacogenomics, 2012 Apr;13(5):533-42.
PMID: 22462746 DOI: 10.2217/pgs.12.24

AIM, MATERIALS & METHODS: We investigated the functional significance of CYP2C19*2, *3, *17 and PON1 Q192R SNPs in 89 consecutive Asian patients on clopidogrel treatment and the prevalence of functionally significant polymorphisms among 300 Chinese, Malays and Asian Indians.

Matched MeSH terms: Ticlopidine/pharmacology