How Is Tylenol Metabolized?

Metabolized In Liver

After you swallow your Tylenol pills, they travel through your bloodstream, which delivers the Tylenol to the liver. The liver is where it is primarily metabolized, or broken down. The liver breaks the pill apart, allowing the acetaminophen to bind to a sulphate molecule and then to bind with a glucuronide molecule. The components that are left after this binding, or metabolizing, are sent out of the body in your urine.

NAPQI

If too much acetaminophen is consumed, the liver cannot handle the metabolizing process. When this occurs, a system called the cytochrome P-450 takes over, forming an intermediate metabolite called NAPQI (N-acetyl-p-benzo-quinone imine). A small amount of this toxic product is always produced from the metabolizing system, but it is a small enough amount to flow out of the body via urine. But when taken in overdose, a larger amount is produced, and its toxicity could cause liver damage.

Interactions

When too much acetaminophen is consumed, and the cytochrome P-450 increases the formation of NAPQI, the glutathione pathway is overwhelmed with NAPQI, and the liver is damaged. Likewise, when alcohol is consumed by itself, the liver is responsible for flushing this product out of the body without harmful effects. When alcohol and Tylenol are consumed together, the liver cannot handle both responsibilities and the liver can be damaged. This is also true with certain drug interactions, such as Tylenol consumed with anticonvulsants, hydantoins or oral anticoagulants.

References

• How Acetaminophen Is Processed In the Body
• Potential Drug-Drug Interactions
• The Effects of Acetaminophen

Resources

• Official Tylenol Website
• Tylenol Review Questions and Answers
• Tylenol and the Liver