May 2009
MedWire News: Aspirin resistance is rare in compliant patients receiving the drug for secondary cardiovascular disease prevention after coronary stenting, being mostly found in noncompliant patients who respond when therapy is controlled, reports a French team.
Thomas Cuisset (CHU Timone, Marseille, France) and colleagues prospectively followed-up 136 consecutive patients undergoing coronary stenting for compliance and aspirin response during hospitalization and at 1 month after hospital discharge. The patients’ aspirin responses were determined using the arachidonic acid-induced platelet aggregation (AA-Ag) assay performed on peripheral blood samples.
The researchers contend that, while several mechanisms have been put forward for the wide variability in antiplatelet therapy response, “the first reason to have inadequate platelet inhibition in patients treated with aspirin is noncompliance.” Thus they hypothesized that aspirin resistance would be rare when assessed by methods that directly measure inhibition of platelet cyclo-oxygenase (COX)-1 activity.
Their results showed that AA-Ag ranged from 0 to 34% during the inhospital phase, at a mean of 7.5%. Four (3%) patients were classed as nonresponders, defined as having AA-Ag >30%, although Cuisset and team note all four had post-treatment AA-Ag lower than 35%.
At 1 month postdischarge, however, AA-Ag ranged from 0 to 94%, with a significantly higher mean compared with the hospital phase, at 15.3% (p=0.004), and 19 (14%) patients were identified as nonresponders.
The 19 nonresponders received controlled intake of oral 75 mg aspirin and their response was reassessed. Only one patient remained a nonresponder.
The authors say a similar pattern was seen using the most common definition of aspirin nonresponse of AA-Ag >20%, with 12 nonresponders in hospital and 32 at 1 month, suggesting a further 18 noncompliant patients who were clearly identified as such following further investigation with the patients, families, and general practitioners. Nine claimed they simply forgot to take their medication, while the other nine stopped because of side effects, mainly gastrointestinal (seven patients) or minor bleeding (two patients).
“Noncompliance should be eliminated before treating with alternative and/or additional antiplatelet medications,” the team concludes in the American Heart Journal.
MedWire is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009
Am Heart J 2009; 157: 889-893
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