There are two errors in this common-but-mistaken belief. First, you should never take acetaminophen (brand name Tylenol) when you've been drinking. Acetaminophen is an over-the-counter pain-relief medication that is processed by your liver -- the same organ responsible for metabolizing any alcohol you consume. After a lot of heavy drinking, since your liver is busy metabolizing the alcohol, any acetaminophen you take (whether Tylenol or a prescription drug containing it like Percocet or Darvocet) is processed by a different metabolic pathway, which can become toxic. You may experience liver inflammation, swelling and even permanent damage. It's much safer to take a nonsteroidal anti-inflammatory drug (NSAID) such as aspirin or ibuprofen [sources: Cicetti, Hudepohl].
But don't take that aspirin or ibuprofen right after drinking. That's the second mistaken notion. When you take one of these medications, it provides the most relief over the next few hours, when you'll likely be asleep and not feeling any pain anyway. Far better to take the pain reliever in the morning. Both of these drugs, by the way, will combat both headache pain and any inflammation in your body [source: Peterson].