title: Cumulative antiplatelet effect of low-dose enteric coated aspirin.
abstract: Enteric coated aspirin (ECA) at doses of 325-1300 mg is an effective alternative to regular aspirin for inhibition of platelet activity while avoiding gastric irritation. The objectives of this study were to determine: (1) the lowest chronic dose of ECA providing effective inhibition of platelet activities, (2) the time course of the inhibition, and (3) the reappearance of platelet cyclo-oxygenase activity. Seven subjects were studied before and after seven daily doses of 40-325 mg ECA. Serum thromboxane (TX) B2 levels indicated that the lowest dose of ECA resulting in greater than 90% inhibition of platelet cyclo-oxygenase was 80 mg/d. Platelet aggregation and ATP release in response to collagen (1 microgram/ml) and arachidonic acid (1 mM) were abolished and bleeding times were prolonged from 6.1 +/- 1.5 min to 9.7 +/- 2.8 min (mean +/- SD, P less than 0.01). Examination of platelet cyclo-oxygenase activity on a daily basis revealed that 24 h after the first 80 mg dose serum TXB2 had decreased by approximately 60% and was suppressed by more than 90% after four doses. Recovery of platelet cyclo-oxygenase activity after a single 80 mg dose of ECA was delayed for 48-72 h indicating that aspirin reached the systemic circulation. We conclude that chronic inhibition of platelet activity may be achieved in a cumulative manner with 80 mg ECA/d.
mesh_terms: D000255:Adenosine Triphosphate / Q000097:blood; D000328:Adult; D001241:Aspirin / Q000008:administration & dosage* / Q000494:pharmacology; D001760:Bleeding Time; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects; D011451:Prostaglandin-Endoperoxide Synthases / Q000097:blood; D013608:Tablets, Enteric-Coated; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D013608:Tablets, Enteric-Coated; D013929:Thromboxane B2; D000255:Adenosine Triphosphate; D011451:Prostaglandin-Endoperoxide Synthases; D001241:Aspirin