Individual dosing of ASA prophylaxis by controlling platelet aggregation.

Acetylsalicylic acid is widely used in the primary and secondary prevention of cardiovascular diseases. In the current study, we used platelet aggregation ex vivo in platelet-rich plasma induced with arachidonic acid as a routine method for the determination of the individual dose of acetylsalicylic acid necessary to inhibit platelet aggregation in 108 patients with cardiovascular diseases. In 40% of all patients studied, a dose of 30 mg/day was sufficient to block the arachidonic acid-induced platelet aggregation nearly completely. In 50% of all patients, a dose of 100 mg/day was necessary. In 10% of all patients, the dose had to be further increased to 300 mg/day or even to 500 mg/day to inhibit platelet aggregation nearly completely. These results demonstrate that platelet aggregation can be used as a simple routine laboratory method to control acetylsalicylic acid treatment in patients with cardiovascular diseases and to determine individual doses of acetylsalicylic acid for a nearly complete inhibition of platelet aggregation. With a standard dose of 100 mg/day, 10% of the patients were nonresponders.