Tylenol PM contains two medications—the pain reliever acetaminophen and an antihistamine (diphenhydramine) to help with insomnia. High doses of acetaminophen can cause liver damage and the risk. How to use Tylenol PM Extra Strength See also Warning section. If you are taking an over-the-counter product, read all directions on the product package before taking this medication. If you are only taking the Tylenol PM at night and not taking any Tylenol-containing products during the day, you will be perfectly fine. If taking more than 4,000mg it can cause liver damage/failure and you should consult your physician. Stop taking Tylenol PM and call your doctor right away if you have skin redness or a rash that spreads and causes blistering and peeling. If you have this type of reaction, you should never again take any medicine that contains acetaminophen. Take the guesswork out. Learn more about TYLENOL® including how much to take, timing your doses, and managing multiple medications. Tylenol is processed in the liver and can be very damaging. Each dose of Tylenol needs to have time to be broken down, processed and moved out of the liver before another dose is given. Four hours between doses is the time frame required for this process. I chose Tylenol PM because its the go to for everyone I know. I who don't even take over the counter drugs or prescriptions am shocked that this is not working for me. I who don't even take over the counter drugs or prescriptions am shocked that this is not working for me. Answer. Many people have trouble falling asleep or staying asleep and find that taking medications can help them get better sleep at night. Tylenol PM is a relatively mild over-the-counter sleep aid that consists of tylenol (a pain reliever) and benadryl (an anti-histamine). Question: Hello Doc – I sometimes end up using Tylenol PM 3 or more times a week to aid in falling asleep and relieve my jaw pain (I`m a sleep clencher – just recently looked into getting a night guard). Can you take Tylenol pm the following day after taking MDMA (molly) to sleep? What happens if you take 4 Tylenol P.M. pills? Can I use Tylenol Night to help me sleep while I'm taking DayQuil?.