DALLAS, TEXAS. Several large scale trials have shown that taking an aspirin as soon as possible after feeling the first pangs of a heart attack can reduce the risk of dying by 23 per cent. Medical doctors at the Texas Southwestern Medical School now report that the aspirin should be chewed rather than swallowed whole in order to minimize the time it takes for the aspirin to take effect. Aspirin works by blocking the synthesis of thromboxane, a metabolite of arachidonic acid, which is involved in the formation of blood clots. The Texas experiment involved 12 healthy volunteers (six women and six men) who, after an overnight fast, swallowed either a chewed Bufferin tablet (325 mg), a whole Bufferin tablet (325 mg) or 4 ounces of water in which an Alka-Seltzer tablet (containing 325 mg of ASA) had been dissolved.

The researchers measured the blood plasma levels of ASA (acetyl salicylic acid), salicylate, and thromboxane B2 (TxB2) immediately before administration of the aspirin as well as 1, 3, 5, 7.5, 10, 15, 20, 30, 60, 120 and 180 minutes after administration. ASA was detectable in the plasma of 10 of the participants within 3 minutes of swallowing a chewed tablet (with 4 ounces of water) and in all 12 by 5 minutes. In contrast, it took 20 minutes before ASA was detected in all participants after swallowing the tablet whole and 10 minutes after taking the Alka-Seltzer. Formation of thromboxane was inhibited by 50 per cent after 5 minutes and by 90 per cent after 14 minutes in the case of the chewed tablet as compared to 12 minutes and 26 minutes and 8 minutes and 16 minutes for the whole tablet and Alka-Seltzer respectively. Considering that it takes about 3 minutes to dissolve an Alka-Seltzer tablet the researchers conclude that by far the quickest way of halting further damage and possibly death during a heart attack is by swallowing a chewed aspirin with water.
Feldman, Mark, and Cryer, Byron. Aspirin absorption rates and platelet inhibition times with 325-mg buffered aspirin tablets (chewed or swallowed intact) and with buffered aspirin solution. American Journal of Cardiology, Vol. 84, August 15, 1999, pp. 404- 09