Read on for Tylenol PM dosage information, including typical dosage and what to do if you take too much. Here’s a closer look at Tylenol PM, its recommended use, and potential side effects. Learn about the side effects of Tylenol PM (acetaminophen/diphenhydramine), from common to rare, for consumers and healthcare professionals. Tylenol PM is a combination medicine used to treat occasional insomnia associated with minor aches and pains. Tylenol PM is not for use in treating sleeplessness without pain, or sleep problems that occur often. Tylenol PM contains two active ingredients: 500 mg of acetaminophen (a pain reliever) and 25 mg of diphenhydramine hydrochloride (an antihistamine that causes drowsiness). The combination is designed to relieve minor aches and pains while helping you fall asleep. Helps you fall asleep, relieves occasional sleeplessness. Easy-swallow softgels, no pain reliever. Adults & 12+. TYLENOL® PM is specifically formulated for minor aches and pains with accompanying sleeplessness. Its combination of acetaminophen and a nighttime sleep aid relieves minor pain and helps you fall asleep.