Thank you for your question and welcome to ADHDCentral.com.
There is no definitive answer to your question as people metabolize medications at different rates. However, homedrugtestingkit.com indicates that the minimum amount of time amphetamines will remain in the system is 2 to 4 hours and the maximum is 2 to 4 days. Therefore, Adderall will probably remain in the system somewhere within this range.
I hope this helps.