title: Resistance to clopidogrel: prevalence and associate variables.
abstract: BACKGROUND
  The dual antiplatelet therapy with acetylsalicylic acid (ASA) and clopidogrel is the cornerstone of treatment for patients undergoing angioplasty with coronary stent implantation. However, some of these patients, despite the use of aspirin and clopidogrel, are not effectively anti-aggregated, a phenomenon known as resistance to antiplatelet agents. Its prevalence, as well as the conditions associated with it, is unknown in our country.
  
  
  OBJECTIVE
  To determine the prevalence of clopidogrel resistance, as well as variables associated with it.
  
  
  METHODS
  Patients admitted for elective angioplasty in chronic use of ASA and clopidogrel between January 2007 and January 2010 were studied. One hour after the procedure, platelet aggregation was measured using optical aggregometry with adenosine diphosphate 5 mmoles / l as agonist. At that moment, in a cross-sectional cohort, we determined the prevalence of clopidogrel resistance, defined as the value of platelet aggregation ≥ 43% and a logistic regression model to the variables associated with it.
  
  
  RESULTS
  A total of 205 patients were analyzed (66.4 ± 11 years, 61.5% males). The prevalence of clopidogrel resistance was 38.5% (95% CI: 31.9 - 45.2%). Blood glucose (OR = 1.014; 95%CI: 1.004 - 1.023), previous myocardial infarction (OR = 2.320; 95%CI: 1.1103 - 4.892) and therapeutic response to ASA (OR = 1.057; 95%CI: 1.017 - 1.099) were the variables independently associated with clopidogrel resistance.
  
  
  CONCLUSIONS
  The prevalence of clopidogrel resistance was high. Glycemia, acute myocardial infarction and response to ASA were variables associated with it. A better understanding of this phenomenon is necessary considering the new antiplatelet aggregant agents.
authors.affiliation: Casa de Saúde São José, Rio de Janeiro, Brasil. fabriciobraga@uol.com.br
authors.forename: Fabrício Braga da
authors.initials: FB
authors.lastname: Silva
authors.forename: Gustavo Luiz Gouvêa de
authors.initials: GL
authors.lastname: Almeida Junior
authors.forename: Augusto
authors.initials: A
authors.lastname: Neno
authors.forename: José
authors.initials: J
authors.lastname: Kezen
authors.forename: Milena
authors.initials: M
authors.lastname: Spelta
authors.forename: Alessandra
authors.initials: A
authors.lastname: Godomiczer
authors.forename: Renato
authors.initials: R
authors.lastname: Villela
authors.forename: Bruno
authors.initials: B
authors.lastname: Hellmuth
authors.forename: Sergio Salles
authors.initials: SS
authors.lastname: Xavier
authors.forename: Roberto Hugo da Costa
authors.initials: RH
authors.lastname: Lins
mesh_terms: D000328:Adult; D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D001241:Aspirin / Q000494:pharmacology; D000077144:Clopidogrel; D004351:Drug Resistance; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D012189:Retrospective Studies; D015607:Stents; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin