Tylenol doesn't work the way we thought it does

Acetaminophen is widely used to relieve pain, but exactly how it works has long been a mystery. Now, a new study suggests that a key byproduct of acetaminophen may block pain signals at the nerves — before they can reach the brain.

Acetaminophen, also called paracetamol or Tylenol, is broken down by the liver into a compound called 4-aminophenol, which travels through the bloodstream to different organs. There, an enzyme links it with a fatty acid to produce AM404.

Previous research found that AM404 can act in the central nervous system — the brain and spinal cord. But the new study, published June 4 in the journal PNAS, reveals that AM404 also affects the peripheral nervous system, where pain signals originate.