Acetaminophen (brand names include Tylenol and Paracetamol) is a safe and effective drug if taken in the proper amounts. Unfortunately, taking 50% more than the recommended daily maximum (four grams for adults) can damage your liver, and taking five times as much can kill you. If you consider the fact that many medicines (such as cold remedies) contain acetaminophen, I think you can see why acetaminophen is the leading cause of acute liver injury in the U.S. It’s just too darn easy to reach those dangerous levels.
There is a treatment for acetaminophen damage. If a patient is given N-Acetylcysteine (N-Ac) within the first twelve hours after overdosing, liver damage can be averted. If a patient doesn’t receive N-Ac during this critical time, it may be too late to save the liver. In that case, the patient’s only chance to live rests with receiving a liver transplant. The problem is that emergency care workers often don’t know whether a patient is or is not within that twelve-hour window. If he is, he should receive N-Ac. If not, giving the patient N-Ac just wastes everyone’s time and may delay putting him on the liver transplant list until it’s too late.
Researchers from the University of Utah decided to see if they could develop a rubric for determining which patients should immediately be placed on the liver transplant list and which should be treated with N-Ac. They used the fact that acetaminophen-caused liver damage follows a known progression. The injured liver releases certain enzymes that peak at a certain number of hours after exposure. The scientists used this data to plot the time and extent of the overdose and to predict which patients would require a liver transplant. Thus far, it appears to be more useful than previous models.
The authors are aware that many confounding factors (other drugs or alcohol, the general health of the patient) will probably affect the efficacy of their model. All the same, it’s a valuable tool for health care providers dealing with an acetaminophen crisis.