Influence of genetic variants and drug interactions on the response to antiplatelet drugs

Antiplatelet therapy plays an important role in the treatment of cardiovascular disease. The combination of acetylsalicylic acid and clopidogrel is routine care in patients with acute coronary syndromes (ACS) or undergoing percutaneous coronary interventions (PCI). Although the effectiveness of antiplatelet therapy is well established, studies have shown interindividual variability in the response to both antiplatelet drugs. This variability in response results in complications at both ends of the therapeutic spectrum (bleeding or thrombosis). Common genetic variations and co-prescribed drugs modify the effectiveness of clopidogrel and acetylsalicylic acid. TH In this thesis, several common genetic variants in enzymes involved in the pharmacokinetics and –dynamics of clopidogrel and acetylsalicylic acid were found to modify the effectiveness of both drugs. Furthermore, the concomitant use of certain proton pump inhibitors, calcium channel blockers and sulfonylureas was associated with an impaired response to clopidogrel

Anaphylaxis after iron dextran administration in a pregnant woman

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Increased frequency of CYP2C19 loss-of-function alleles in clopidogrel-treated patients with recurrent cerebral ischemia

AIMS: Clopidogrel is used as secondary prevention after cerebral ischaemia. Previous, mainly Asian, studies have shown that genetic variations in CYP2C19 are associated with an increased risk of recurrent stroke in clopidogrel-treated patients. Evidence on the impact of this drug-gene interaction in European neurology patients is currently limited. The aim of this study is to compare the prevalence of CYP2C19 loss-of-function (LoF) alleles in a population with recurrent cerebral ischaemia to two reference groups from the same region. METHODS: CYP2C19-genotyping (*2 and *3) was performed in clopidogrel-treated patients who presented with a recurrent ischaemic stroke/transient ischaemic attack (TIA). Genotype distributions were compared with two reference groups; a cohort of consecutive patients who underwent elective coronary stent implantation and a cohort of healthy Dutch volunteers. RESULTS: In total, 188 cases with a recurrent ischaemic event were identified, of whom 38 (20.2%) experienced an early recurrent event (24 hours to 90 days after the previous event). Among the total case group, 43.6% of the patients carried at least one CYP2C19 LoF allele, compared with 27.6% and 24.7% in respectively the cardiology and the healthy volunteers reference groups (P < .001 for both comparisons). Among the cases with an early recurrent event, 55.3% of patients were carriers of at least one CYP2C19 LoF allele (P < .0001). CONCLUSION: In this clopidogrel-treated population with recurrent cerebral ischaemia, the frequency of CYP2C19 LoF alleles was significantly higher than in reference groups, especially in early recurrent events. This study adds to the growing body of evidence that genotype-guided antiplatelet therapy could improve patient outcomes

Role of Drug-Gene Interactions and Pharmacogenetics in Simvastatin-Associated Pulmonary Toxicity

Introduction Simvastatin has previously been associated with drug-induced interstitial lung disease. In this retrospective observational study, cases with non-specific interstitial pneumonia (NSIP) or idiopathic pulmonary fibrosis (IPF) with simvastatin-associated pulmonary toxicity (n = 34) were evaluated. Objective To identify whether variations in genes encoding cytochrome P450 (CYP) enzymes or in the SLCO1B1 gene (Solute Carrier Organic anion transporting polypeptide 1B1 gene, encoding the organic anion transporting polypeptide 1B1 [OATP1B1] drug transporter enzyme), and/or characteristics of concomitantly used drugs, predispose patients to simvastatin-associated pulmonary toxicity. Methods Characteristics of concomitantly used drugs and/or variations in the CYP or SLCO1B1 genes and drug-gene interactions were assessed. The outcome after withdrawal of simvastatin and/or switch to another statin was assessed after 6 months. Results Multiple drug use involving either substrates and/or inhibitors of CYP3A4 and/or three or more drugs with the potential to cause acidosis explained the simvastatin-associated toxicity in 70.5% (n = 24) of cases. Cases did not differ significantly from controls regarding CYP3A4, CYP2C9, or OATP1B1 phenotypes, and genetic variation explained only 20.6% (n = 7) of cases. Withdrawal of simvastatin without switching to another statin or with a switch to a hydrophilic statin led to improvement or stabilization in all NSIP cases, whereas all cases who were switched to the lipophilic atorvastatin progressed. Conclusion Simvastatin-associated pulmonary toxicity is multifactorial. For patients with this drug-induced pulmonary toxicity who need to continue taking a statin, switching to a hydrophilic statin should be considered. ClinicalTrials.gov identifier NCT00267800, registered in 2005

[Interaction between clopidogrel and proton pump inhibitors]

Item does not contain fulltextThe drug interaction between proton pump inhibitors and clopidogrel has been the subject of much study in recent years. Contradictory results regarding the effect of proton pump inhibitors on platelet reactivity and on clinical outcome in clopidogrel-treated patients have been reported in literature. Concomitant use of omeprazole and clopidogrel was found to decrease the exposure (AUC) to clopidogrel's active metabolite by 50% and to sharply increase platelet reactivity, as a result of inhibition by omeprazole of CYP2C19, a cytochrome P450 (CYP) enzyme. Pantoprazole has a much weaker effect on clopidogrel's pharmacokinetics and on platelet reactivity during concomitant use. The influence of the other proton pump inhibitors when used simultaneously with clopidogrel has not yet been investigated in adequately randomized studies. Regulatory agencies state that the combination of clopidogrel and the CYP2C19 inhibitors omeprazole and esomeprazole should be avoided. To date, there is no conclusive evidence of a clinically-relevant interaction between any of the proton pump inhibitors and clopidogrel

Combined influence of proton-pump inhibitors, calcium-channel blockers and CYP2C19*2 on on-treatment platelet reactivity and on the occurrence of atherothrombotic events after percutaneous coronary intervention

Background: The carriage of CYP2C19*2 and the use of proton-pump inhibitors (PPIs) and calcium-channel blockers (CCBs) has been associated with the diminished efficacy of clopidogrel. However, previous studies have only assessed the isolated impact of these risk factors for clopidogrel poor response. Objectives: The aim of the present study was to investigate the impact of the combined presence of three risk factors for clopidogrel poor response, that is, the use of CCBs, PPIs and the carriage of CYP2C19*2, on on-treatment platelet reactivity and the occurrence of atherothrombotic events in 725 patients on dual antiplatelet therapy undergoing elective coronary stenting. Methods: In a prospective, follow-up study, on-treatment platelet reactivity was quantified using ADP-induced light transmittance aggregometry (LTA) and the VerifyNow P2Y12 assay. The clinical study endpoint was the composite of all-cause mortality, myocardial infarction, stent thrombosis and stroke at 1year after stenting. Results: Patients with either one or more than one risk factor exhibited increased platelet reactivity (mean relative increase one risk factor: 11% and >1 risk factor: 22%, respectively). Sixty-four events occurred during follow-up (8.8% of the study population). Patients with one risk factor for clopidogrel poor response did not have an increased risk of the composite endpoint. However, patients using both CCBs and PPIs and carriers of CYP2C19*2 who used CCBs had a statistically significant increased risk of the composite endpoint [hazard ratio(HR)adj2.2 95% CI, 1.0-5.3, P=0.044 and HRadj3.3 95% CI, 1.1-9.8, P=0.032, respectively]. Conclusions: The presence of more than one of the three investigated risk factors for clopidogrel poor response is associated with an increased risk of adverse cardiovascular events within 1year after elective coronary stenting. © 2011 International Society on Thrombosis and Haemostasis