Influence of low dose enteric-coated aspirin on platelet function.

Little is known about the effect of low dose, enteric-coated aspirin on human blood platelet function. This study was conducted to evaluate the acute effects of a single daily dose of commercially available enteric-coated aspirin on platelet biochemistry, physiology and function. Blood for these studies was obtained from drug-free volunteer donors prior to ingestion of aspirin or following ingestion, either before breakfast or following lunch. Response of platelets to the action of weak agonists was evaluated. In addition, ability of platelets to convert radiolabeled arachidonic acid to thromboxane was monitored. Results of our studies show that a single daily dose of 50 mg of aspirin taken either before breakfast or after lunch effectively prevented the secondary wave aggregation response, as well as secretion of dense body contents when stimulated by agonists such as epinephrine and ADP. Aspirin ingestion caused a dose-dependent inhibition of platelet cyclooxygenase activity as evidenced by the extent of arachidonic acid converted to thromboxane by platelets exposed to aspirin for different time periods. Based on these observations, it is suggested that low dose aspirin may be very useful and desirable to restrain platelet activity in clinical situations in which increased thromboxane formation may initiate vascular hypertension and platelet hyperactivity.