Researchers at the University of Seattle in Washington have done a study to see what effect Tylenol and coffee have on the liver.
The published results warn that the combination of Tylenol and Caffeine actually triples the amount of a toxic Tylenol by-product - N-acetyl-p-benzoquinoneimine (NAPQI). This is especially true for heavy caffeine drinkers. Toxins in the body are filtered by the liver, so this by-product poses a large burden on the liver.
The liver works constantly to help the body maintain a state of balance - it is one of the body's filtering mechanisms. Many medications are broken down in the liver. You can imagine the increased burden if you have any pre-existing liver problems or are already taking other medications, so beware.
The combination of alcohol and Tylenol (Acetomenophen) is a known toxic combination, for the same reasons as above - the Tylenol interacts with the alcohol, releasing the toxic enzyme and causing liver damage and possibly liver failure.
Think twice before you choose your hangover or headache remedy. The combination of alcohol the night before, several cups of coffee in the morning and Tylenol should really be avoided.