I have been taking aspirin 300mg daily for 1 week and its affecting my asthma giving me breathing problems,yesterday i took the last 300mg pill,in how much time my body will get rid of the aspirin effect and return to his normal state?

The time for 1/2 to leave the body from a single dose is 4-7 hours (half-life). It takes 4 half-lives to be considered at a negligible level. Some asthma patients can be triggered by any form of salicylate drug.

Aspirin sensitive asthmatics should try to avoid the use of aspirin and aspirin based products. Other options for fever control and aches are NSAIDS.