Aspirin absorption rates and platelet inhibition times with 325-mg buffered aspirin tablets (chewed or swallowed intact) and with buffered aspirin solution

Large clinical trials such as the second International Study of Infarct Sur vival routinely gave patients with myocardial infarction a chewed aspirin, yet there are no data to show whether chewing of aspirin is better, or wors e, than swallowing a whole tablet. We performed a randomized, placebo-contr olled study to determine whether chewing aspirin or administering it in sol ution accelerates its absorption and antiplatelet activity. On separate day s, 12 fasting volunteers ingested 325 mg of buffered aspirin, either by che wing a tablet for 30 seconds before swallowing it with 4 ounces of water, s wallowing a whole tablet with 4 ounces of water, or drinking 4 ounces of Al ka Seltzer. Frequent blood samples were obtained for serum aspirin, salicyl ate, and thromboxane B-2 (TxB(2)) concentrations. With all formulations of aspirin, serum TxB(2) decreased 50% when the plasma aspirin concentration r eached approximately 1,000 ng/ml, A 50% and 90% decrease in serum TxB(2) oc curred more quickly after chewing a tablet than after a tablet was swallowe d whole. For example, the t 50% for serum TxB(2) inhibition was 5.0 +/- 0.6 minutes with the chewed tablet versus 12.0 +/- 2.3 minutes when the tablet was swallowed (p = 0.01). A 50% decrease in serum TxB(2) occurred 7.6 +/- 1.2 minutes after Alka Seltzer solution (p = 0.04 vs chewing a tablet; p = 0.13 vs swallowing a whole tablet). Chewing an aspirin tablet is the most e ffective way of accelerating absorption of aspirin into the blood and short ening the time required for an anti-platelet effect, (C) 1999 by Excerpta M edica, Inc.