Tylenol, also known as acetaminophen, is a popular over-the-counter medication for relieving pain and fever. However, when used excessively (especially during overdose), it is quite toxic and is one of the leading causes of acute liver failure. The mechanism behind Tylenol's toxicity is that in the liver it is converted to secondary metabolites, some of which are quite toxic. The body has systems in place to handle such toxicity, but in cases of acute overdose, these systems can be overwhelmed. Resulting toxicity to the liver ensues and can be divided into four phases.
Phase 1
This occurs in the first 30 minutes or up to 24 hours after ingestion. Patients are typically asymptomatic and appear quite normal, but nausea and vomiting can occur.
Phase 2
This occurs between 24 to 72 hours after ingestion. Pain will begin to be noticed, usually located in the right upper quadrant of the abdomen, which is right underneath the right nipple. This corresponds to the liver's anatomical location in the body. Signs of liver failure, such as increased propensity to bleed, can be seen, as the liver is responsible for synthesizing many clotting factors. Damage to the kidney may also be seen, with decreased urine output being a primary sign.
Phase 3
This occurs between 72 to 96 hours after ingestion, and is commonly where clinical death occurs. Liver failure tends to worsen, and the consequences are numerous. They include jaundice, increased bleeding tendencies and severe damage to the kidneys. Many experts recommend liver transplant at this stage if possible to increase chances of survival. The next stage is only entered if the patient survives this phase.
Phase 4
This is the recovery phase, in which the liver and kidneys usually recover fully. No signs of damage usually remain, such as scarring or fibrosis of the organs involved.
References
- Annals of Emergency Medicine. "Development of Hepatic Failure Despite Use of Intravenous Acetylcysteine After a Massive Ingestion of Acetaminophen and Diphenhydramine." Schwartz E, Hayes B, Sarmiento K. Volume 54, Issue 3 (September 2009)
- Medical Clinics of North America. "Acute Liver Failure Including Acetaminophen Overdose." Fontana R. Volume 92, Issue 4 (July 2008)
- Haddad and Winchester's Clinical Management of Poisoning and Drug Overdose, 4th ed. Shannon 2007
