As Jaybay said it
is in your system for about 6 hours. The bigger risk I see
is consuming alcohol with acetaminophen (tylenol).
It is a statistical fact that alcohol and acetaminophen can (in some cases) case serious liver damage, even with a one time mixture. Alcohol appears to activate the enzyme CYP2E1 in the liver. That enzyme may be responsible for transforming acetaminophen into chemicals that can cause liver damage, even when acetaminophen is taken in standard therapeutic doses.