SHEET /vs/aspirin-vs-ibuprofen · COMPARISON
Aspirin vs Ibuprofen: what is the difference?
How they differ
from source
Both are NSAIDs that work by blocking COX enzymes, and both carry a carboxylic acid on an aromatic ring, so they are far closer relatives than either is to acetaminophen. The difference is reversibility. Aspirin acetylates the enzyme permanently, so its effect on platelets outlives the molecule in the blood, which is the basis of its use in cardiology. Ibuprofen binds and lets go, so its effect fades as it clears, with a half-life near 2 hours. Ibuprofen is also the more potent anti-inflammatory at the doses people actually use, and it is the newer molecule by seventy years. Reported oral LD50 in rats is 200 mg/kg for aspirin and 636 mg/kg for ibuprofen.
Side by side
| Aspirin | Ibuprofen | |
|---|---|---|
| Formula | C9H8O4 | C13H18O2 |
| Molecular weight | 180.16 g/mol | 206.28 g/mol |
| Family | Over-the-counter medicines, NSAIDs, Non-opioid painkillers | Over-the-counter medicines, NSAIDs, Non-opioid painkillers |
| Everyday group | OTC medicine | OTC medicine |
| Functional groups | Carboxylic Acids, Aromatics, Esters | Carboxylic Acids, Aromatics |
| GHS signal wordThe supplier-filed hazard label, not a statement about ordinary use. | Danger | Danger |
| Oral LD50A single acute animal measure. It ranks nothing about human safety. | 200 mg/kg (oral, rat) | 636 mg/kg (oral, rat) |
| Half-life | not recorded | 2 h |
| Also sold as | Bayer, Bufferin, Ecotrin | Advil, Motrin, Nurofen |
| CAS number | 50-78-2 | 58560-75-1 |
| PubChem CID | 2244 | 3672 |
Common questions
- What is the difference between Aspirin and Ibuprofen?
- Both are NSAIDs that work by blocking COX enzymes, and both carry a carboxylic acid on an aromatic ring, so they are far closer relatives than either is to acetaminophen. The difference is reversibility. Aspirin acetylates the enzyme permanently, so its effect on platelets outlives the molecule in the blood, which is the basis of its use in cardiology.
- Is Aspirin bigger than Ibuprofen?
- Ibuprofen is the heavier molecule, 206.28 g/mol against 180.16 g/mol for Aspirin. Aspirin is C9H8O4 and Ibuprofen is C13H18O2.
- Which has the lower reported LD50, Aspirin or Ibuprofen?
- Aspirin, at 200 mg/kg (oral, rat), against 636 mg/kg (oral, rat) for Ibuprofen. 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.