How long is aspirin effective in your body?

Answer 1

Most people these days take aspirin due to it's antiplatelet aggregation effects, and not as a pain reliever for something like a headache. For that reason it is commonly referred to as a "blood thinner", but this is a misnomer.

Aspirin works to make platelets more "slippery" and less able to bind to other platelets or to sites of injured endothelial tissue by permanently binding to cyclooxgenase (COX) molecules on the surface of platelets thereby preventing the formation of thromboxane A2 (TXA2). Thus aspirin acts by inhibiting the ability of the COX enzyme to produce the precursors of thromboxane within platelets. This maintains the platelet in an inactive state and prevents platelet aggregation and coagulation for the life of the platelet.

The elimination half life of aspirin (salicylic acid) in a healthy individual is approximately 6 hours. But since the normal lifespan of a platelet is 8 to 10 days, the effects of aspirin can be seen for more than 8 days, or until all the aspirin inactivated platelets are replaced in your circulatory system. Many medical practitioners consider the antiplatelet aggregation action of aspirin to still be effective 5 days after the last dose of aspirin was taken.

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