[Reversible inhibition of thrombocyte stimulation by acetylsalicylic acid and its role in antithrombotic therapy]

Plasma salicylate levels and platelet function after acute and chronic administration of slow-release acetylsalicylic acid (Monobeltin)

The relationships between the antiplatelet effects and the pharmacokinetics of a slow release formulation of acetylsalicylic acid (ASA) have been investigated. After acute intake of 750 mg ASA in a slow-release formulation (Monobeltin), a slow increase in plasma ASA was paralleled by a gradual decrease in certain platelet functions. During chronic medication (750 mg twice daily), ASA was present in plasma at all times accompanied by full inhibition of platelet aggregation. For chronic antiplatelet therapy, this slow release formulation of ASA appears to be very effective, unless rapid inhibition of platelet function must be achieved.

[Effects of acetylsalicylic acid on partial functions of human thrombocytes are not inhibited in vivo by salicylic acid]

Acetylsalicylic acid inhibits platelet function. In plasma acetylsalicylic acid is rapidly deacetylated to salicylic acid which is slowly eliminated and has no direct inhibitory effects on platelet function. However, salicylic acid prevents the inhibition by acetylsalicylic acid of collagen-induced aggregation of human thrombocytes in vitro. It was suggested that salicylic acid might inhibit the antiplatelet effects of acetylsalicylic acid in vivo and therefore low-dose acetylsalicylic acid would be more effective for antithrombotic therapy. A 500-mg tablet of acetylsalicylic acid applied 90 min after oral administration of 500 mg salicylic acid to six healthy male volunteers led to the same inhibition of collagen-induced platelet aggregation and tissue-extract-induced platelet stimulation as 500 mg acetylsalicylic acid alone. These results cannot give additional support to the recommendation of low-dose acetylsalicylic acid in the prevention of thromboembolic disease.