acetaminophen
Meaning of acetaminophen: Known as paracetamol outside the United States, and present in so many combination products that a total intake is easy to lose track of.
Definition of acetaminophen
Acetaminophen is a medicine that relieves mild to moderate pain and lowers fever. It is sold without a prescription under many brand names and is also an ingredient in a large number of combination cold, flu and pain products. Unlike ibuprofen and related drugs, it has little effect on inflammation.
How does it differ from ibuprofen and aspirin?
Those drugs belong to a separate class, the nonsteroidal anti-inflammatory drugs, and the difference is not a matter of strength but of where and how each acts.
| Property | Acetaminophen | NSAIDs such as ibuprofen and naproxen |
|---|---|---|
| Relieves pain | Yes | Yes |
| Lowers fever | Yes | Yes |
| Reduces inflammation | Little to none | Yes, which suits swollen joints and injury |
| Effect on the stomach lining | Minimal | Can cause irritation, ulcers and bleeding |
| Effect on blood clotting | None | Reduces platelet function |
| Organ most at stake in excess | The liver | The kidneys and the gut |
That is why a nonsteroidal anti-inflammatory drug is preferred for an inflamed joint while acetaminophen is often chosen where stomach, kidney or bleeding concerns rule those out. Its exact mechanism remains uncertain; the best supported explanation is that it acts within the central nervous system on pain signaling and on the brain's temperature set point rather than at the injured tissue.
What does the liver do with it?
Most of a normal amount is attached to another molecule in the liver and passed harmlessly into the urine. A small fraction takes a second route and becomes a highly reactive compound, which the liver neutralizes with glutathione, a protective molecule held in reserve. The system works until that reserve runs down. Once it does, the reactive compound attacks liver cells directly, and injury follows some hours later, after the point at which a person feels anything wrong. Acetaminophen taken beyond recommended amounts is among the leading causes of sudden liver failure in countries where it is widely sold.
Why do combination products complicate it?
Acetaminophen appears in nighttime cold remedies, sinus tablets, menstrual pain products and many prescription opioid painkillers, sometimes under an abbreviation rather than its full name. Two over-the-counter products taken together, or one taken alongside a prescription combination, can add up to far more than either package suggests, which is the most common route to an unintentional excess. Regular heavy alcohol use and prolonged fasting both lower the protective reserve, which is why the same amount does not carry the same margin for everyone.
Also known as
Used in a sentence
The pharmacist noted that acetaminophen was present in both the prescription and over-the-counter medication the patient was taking.
Good to know
Acetaminophen appears as an ingredient in numerous combination products, so combining separate medications without checking their ingredients can result in a higher total dose than expected.