Repeated doses of slightly too much Tylenol can be fatal. These patients had a higher fatality rate than single doses taken as a suicidal attempt. It take about 15 grams of a single dose to lead to liver failure and the possible need for a liver transplant. Taking just 3 times the recommended dosage can lead to liver failure and death in some people. Generally these people are older and tend to drink too much. One quarter of all liver transplants or fatalities are in these people taking slightly higher doese than recommended.
Liver detoxification with N-acetyl cysteine (NAC) may be compromised and explain why relatively small over doses of this toxin (acetamenophen) can be fatal. Treatment should always include NAC as soon as possible as it may allow the detoxification and excretion of Tylenol much faster.
It is interesting that aspirin, Tylenol and NSAIDs such as ibuprofen inhibit an enzyme called cytochrome C oxidase, which leads to a deficiency of ATP (the energy currency of our cells) and further damage to the liver. It is also little known that Tylenol in dosages above 2 grams a day causes bleeding just like aspirin. Tylenol is not an ideal drug to use and certainly it should not be used in hospitals where detoxification is often a very significant problem.