How long does it take tylenol (acetaminophen) extra strength to work?

Acetaminophen: Onset of action of oral acetaminophen is less than one hour. Duration of action is about 4-6 hours. Please be careful with this drug. Never take more than 3000 mg per day. Take even less if you have any liver problems. Never combine this or any prescription medication with alcohol. The most common form of attempted suicide in the U.S. is intentional acetaminophen overdose. Be careful, please.