Tylenol PM typically remains in an adult's system for 6 to 8 hours. However, times can be shorter or longer depending on how the body metabolizes the drug.
Tylenol PM contains two active ingredients: acetaminophen, which is a pain reliever, and diphenhydramine, which is a sleep aid. Tylenol PM is meant for adults and children 12 years and older. Users of Tylenol PM should not consume more than two caplets in a 24-hour period. Furthermore, in case of any irritation to the skin, users should cease consumption of the product, as it may be a symptom of an allergic reaction.