Acetaminophen vs Aspirin: what is the difference?
Aspirin blocks COX enzymes irreversibly and affects platelets for days, while acetaminophen works centrally and leaves inflammation and clotting alone.
Sources and notes
- The sentence under the titlefrom sourceMoleculeFinder comparison notesThe pair's answer line.
- The two drawingscomputedMoleculeFinder rule (RDKit MCS)Drawn the same way round on the skeleton they share. Aligned; 10 atoms differ, too many to mark as one group.
Side by side
| Acetaminophen | Aspirin | |
|---|---|---|
| Molecular weightCalculated PubChem | 151.16 g/molC8H9NO2 | 180.16 g/molC9H8O4 |
| Hydrogen-bond donorsCalculated PubChem | 2 | 1 |
| Half-life in the bodyEditorial MoleculeFinder curated | about 2 h | Not recorded |
| Where each turns upEditorial MoleculeFinder food and product lists |
|
|
| Also sold asEditorial MoleculeFinder curated | Tylenol | Bayer, Bufferin, Ecotrin |
| FamilyEditorial MoleculeFinder curated | Over-the-counter medicines, Non-opioid painkillers | Over-the-counter medicines, NSAIDs, Non-opioid painkillers |
| Everyday groupEditorial MoleculeFinder curated | OTC medicine | OTC medicine |
| Chemical groupsCalculated Found by rule (RDKit) | Aromatics, Amides, Phenols | Carboxylic Acids, Aromatics, Esters |
| Hazard labelReported ECHA, HSDB via PubChem; ECHA via PubChem | Warning | Warning |
| The supplier-filed hazard label's signal word, not a statement about ordinary use. | ||
| Oral LD50Measured HSDB via PubChem | 2,400 mg/kgpure acetaminophen, rat, oral | 200 mg/kgpure aspirin, rat, oral |
| A single acute animal measure. It ranks nothing about human safety. | ||
Sources and notes
- Molecular weightcomputedPubChemComputed from the structure; the formula is under each weight.
- Hydrogen-bond donorscomputedPubChemThe hydrogens on nitrogen or oxygen that each molecule can lend to a hydrogen bond, counted from its structure.
- Half-life in the bodyfrom sourceMoleculeFinder curatedIn a typical adult: the time the body takes to clear half of it.
- Where each turns upfrom sourceMoleculeFinder food and product listsEach amount is an editorial figure from our lists, not a measurement of any one product. Each mark is set by hand on the list, never inferred.
- Also sold asfrom sourceMoleculeFinder curated
- Familyfrom sourceMoleculeFinder curated
- Everyday groupfrom sourceMoleculeFinder curated
- Chemical groupscomputedFound by rule (RDKit)Each group is found in the structure by a chemical pattern.
- Hazard labelfrom sourceECHA, HSDB via PubChem; ECHA via PubChem
- Oral LD50from sourceHSDB via PubChem
- ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
- Identifiersfrom sourcePubChemPubChem CID 1983 (Acetaminophen) and 2244 (Aspirin).
In more detail
Aspirin is the older molecule by a century and the more chemically aggressive of the two. It is acetylsalicylic acid, made by acetylating willow-bark salicylic acid in 1897, and it blocks the COX enzymes irreversibly, which is why a single exposure affects platelets for days. Acetaminophen does not do that at all: it works centrally, has little anti-inflammatory effect, and leaves clotting alone. The table shows aspirin's carboxylic acid and ester against acetaminophen's amide and phenol, which is the structural reason aspirin irritates a stomach lining and acetaminophen does not. Reported oral LD50 in rats is 200 mg/kg for aspirin against 2400 mg/kg for acetaminophen, an unusually wide gap for two drugs sold on the same shelf.
Sources and notes
- The paragraphfrom sourceMoleculeFinder comparison notes
Questions
- What is the difference between Acetaminophen and Aspirin?
- Aspirin blocks COX enzymes irreversibly and affects platelets for days, while acetaminophen works centrally and leaves inflammation and clotting alone.
- Is Acetaminophen bigger than Aspirin?
- Aspirin is the heavier molecule, 180.16 g/mol against 151.16 g/mol for Acetaminophen. Acetaminophen is C8H9NO2 and Aspirin is C9H8O4.
- Which has the lower reported LD50, Acetaminophen or Aspirin?
- Aspirin, at 200 mg/kg (oral, rat), against 2,400 mg/kg (oral, rat) for Acetaminophen. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.
Sources and notes
- The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.