SHEET /vs/acetaminophen-vs-ibuprofen · COMPARISON
Acetaminophen vs Ibuprofen: what is the difference?
How they differ
These are the two painkillers most households keep, and they are not the same kind of drug. Ibuprofen is an NSAID: it blocks the COX enzymes throughout the body, which is why it reduces inflammation and swelling as well as pain. Acetaminophen, called paracetamol outside the US, acts mainly in the central nervous system and does very little for inflammation, which is why a sprain and a headache are not the same problem for it. The functional groups in the table show the split, ibuprofen carrying a carboxylic acid and acetaminophen an amide and a phenol. Their reported oral LD50 values differ by a factor of three, 1944 mg/kg in rats for acetaminophen against 636 mg/kg for ibuprofen, though the risks that actually matter for each are organ specific rather than a matter of the headline number.
Side by side
| Acetaminophen | Ibuprofen | |
|---|---|---|
| Formula | C8H9NO2 | C13H18O2 |
| Molecular weight | 151.16 g/mol | 206.28 g/mol |
| Family | Over-the-counter medicines, Non-opioid painkillers | Over-the-counter medicines, NSAIDs, Non-opioid painkillers |
| Everyday group | OTC medicine | OTC medicine |
| Functional groups | Aromatics, Amides, Phenols | 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. | 1,944 mg/kg (oral, rat) | 636 mg/kg (oral, rat) |
| Half-life | 2 h | 2 h |
| Also sold as | Tylenol | Advil, Motrin, Nurofen |
| CAS number | 103-90-2 | 58560-75-1 |
| PubChem CID | 1983 | 3672 |
Common questions
- What is the difference between Acetaminophen and Ibuprofen?
- These are the two painkillers most households keep, and they are not the same kind of drug. Ibuprofen is an NSAID: it blocks the COX enzymes throughout the body, which is why it reduces inflammation and swelling as well as pain. Acetaminophen, called paracetamol outside the US, acts mainly in the central nervous system and does very little for inflammation, which is why a sprain and a headache are not the same problem for it.
- Is Acetaminophen bigger than Ibuprofen?
- Ibuprofen is the heavier molecule, 206.28 g/mol against 151.16 g/mol for Acetaminophen. Acetaminophen is C8H9NO2 and Ibuprofen is C13H18O2.
- Which has the lower reported LD50, Acetaminophen or Ibuprofen?
- Ibuprofen, at 636 mg/kg (oral, rat), against 1,944 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.
Read the full records: Acetaminophen and Ibuprofen.