What form of Aspirin for Stroke?

I'm an EMT and when we have a chest pain call one of the first things we do is have the pt chew 325 mg (4 baby) aspirin. Chewing it gets it absorbed very quickly and doesn't negatively affect anything - except it tastes like crap! Bad taste is worth a life saved though.

First, there is regular aspirin that isn't enteric coated. The coating is to protect your stomach from the acidity of the aspirin (acetylsalicylic acid), and to protect the aspirin from the low pH of the stomach; the lower pH keeps it in the acid form, and not the salt form that is needed to be absorbed orally in the small intestine. What the enteric coating is doing is allowing the aspirin tablet to hold off dissolving in the stomach, and allows it to dissolve in the higher pH of the small intestine (pH of around 6 compared to 2 in the stomach). It takes around 6 hours for effective plasma levels to be achieved with an oral enteric coated tablet, and the enteric coated aspirin should only be used daily to help prevent a stroke or heart attack, because it is giving around the clock protection. Taking the uncoated aspirin, it takes roughly 15 to 30 minutes to enter the small intestine and begin absorbing to achieve effective plasma levels. I do have to disagree with the EMS answer to take 325 mg of aspirin. 325 mg of aspirin will work, but it will not work as well at inhibiting platelet aggregation as 81 mg or 162 mg (2 81mg tablets) This is due to at the plasma concentration of the 81 mg aspirin dose; aspirin is inhibiting prostaglandin E2 (PGE2), and thromboxane A2 (TXA2), without inhibiting prostacyclin (PCI). PGE2 and TXA2 are responsible for the platelets sticking together, and PCI is a natural factor that inhibits platelet aggregation. At the 81-162 mg dose, PCI isn't effected. At the 325 mg dose, it is starting to affect PCI effects, as well as inhibiting PGE2 and TXA2. 325 mg is the maximum dose that we recommend for anti-coagulation after a stroke "cerebrovascular accident" (CVA), or heart attack "acute myocardial infarction" (AMI). The dose of 162 mg is actually the most effective dose for anti-coagulation. After 325 mg, PCI is completely inhibited, and this negates the effect of aspirin as a blood thinner. I do agree with the EMS that if all you have is enteric coated aspirin when experiencing one of the events, that chewing the tablet is the best way to increase absorption, and minimize the time to achieve therapeutic plasma concentrations.