Aspirin resistance - does it clinically matter?

A variable responsiveness to acetylsalicylic acid(ASA) is a clinical reality that does not principally differ from variable responses to other kinds of drug treatment in other therapeutic fields. Two questions arise: (i) is any resulting "treatment failure"due to a pharmacological failure of the drug to act and (ii) is any reduced antiplatelet activity to ASA related to the clinical outcome oft he patient?Two major laboratory techniques are available to quantify platelet variability to ASA ex vivo: Measurement of platelet function and measurement of thromboxane formation. Both methods have limitations and did not yet result in a generally accepted definition of a pharmacological ASA "resistance".A "true" pharmacological resistance to ASA exists in selected groups of patients. However, unless more information is available,results from in vitro assays of platelet function should not be over-interpreted. More data from prospective trials are required,predominantly by measuring serum thromboxane formation which is a platelet-specific, ASA sensitive reaction. At this time,there is no reason to change there commended daily maintenance dose of about 100 mg ASA without particular requirements in patients who need coronary protection.