Took arimidex (anastrozole) for 3mo3wks stopped for 10days now. how long will my system take to return to normal?

Arimidex (anastrozole): The half-life is 46.8 hours so roughly round that off to 48 hours for two days. We consider a medication to be out of the person system once five half-lives have elapsed. In your case that would be there in 10 days after stopping the medication. Therefore it should be out of your system at this point. Best wishes and have a happy new year.