Never take Tylenol PM to sleep, unless you also have a reason to need a painkiller (acetaminophen). Acetaminophen is toxic to the liver and can cause liver failure if overdosed. A regular diphenhydramine (Benadryl) is the just the PM part without the extra risk (except that has its own risks).
It has a therapeutic index of 10, which is quite low (easy to overdose). I stopped taking Paracetamol almost completely after learning what it can to your body.
Also, there was a story about the developer of DirectX who alledgedly overdoesed on Paracetamol/Tylenol:
Perhaps never is a bit extreme here? You make a good point but if it's all you've got and you haven't been drinking it isn't going to hurt you. It's got a normal dose of acetaminophen last I checked.
This is all assuming it isn't being used for some kind of chronic sleep issue.
