RESUMO
The authors determined the rate of acetylsalicylic acid (ASA) non-responders among patients receiving secondary prevention due to cardiovascular diseases at the appearance of acute coronary events. The non-responders were defined as: patients who have been treated with ASA because of acute coronary syndrome, but the subsequently performed platelet aggregation study did not confirmed an appropriate platelet inhibition. Among the 75 patients being investigated (44 male, 31 female, average age: 61.3 ys) 21 were hospitalized due to acute myocardial infarction and 54 for unstable angina, respectively. The daily doses of ASA were 200-325 mg. The aggregation of platelets was measured within 24 h after the admission. The investigations were performed with different amounts of 4 different inducers (ADP, arachidonic acid, epinephrine and collagen) taking dose-response curves. The antiaggregatory treatment with ASA was considered to be ineffective if the typical aggregation curves were obtained above the following final concentrations of the inducers: ADP: > 5 microM, epinephrine: > 5 microM, arachidonic acid: > 250 microM, collagen: > 2 micrograms/ml. These upper-threshold concentrations of the inducers were determined with the help of the data of healthy drug free volunteers. Twenty-six of the 75 patients (34%) were found to be non-responder to ASA, whereas the antiaggregatory effect of ASA was proven in 49 cases. No differences were found in gender. The compliance was proven with the HPLC-determination of urinary metabolites of ASA performed immediately after the upon admission. Seven patients (10.9%) showed a non-compliance, not showing any traces of ASA-metabolites in their urine. The authors emphasizing the importance of the laboratory control even of the prophylactic ASA treatment in order to continue the effective antiaggregatory therapy with other effective drugs.
