Paracetamol vs ibuprofen.
These are the two drugs every household holds and the two students most often treat as interchangeable. They are not. One reduces inflammation and threatens the stomach and kidney; the other does neither and threatens the liver only if the dose is exceeded.
Ibuprofen inhibits COX peripherally, so it is anti-inflammatory and carries gastric and renal risk. Paracetamol acts largely centrally, is not meaningfully anti-inflammatory, and is safe at therapeutic doses but causes hepatic necrosis in overdose through a toxic metabolite.
Paracetamol vs Ibuprofen at a glance
| Property | Paracetamol | Ibuprofen |
|---|---|---|
| Main site | Central | Peripheral and central |
| Anti-inflammatory | No meaningful effect | Yes |
| Antipyretic | Yes | Yes |
| GI risk | Minimal | Significant |
| Renal risk | Minimal at therapeutic doses | Significant |
| Organ at risk in overdose | Liver | Relatively low toxicity in overdose |
| Antidote | Acetylcysteine | None specific |
Why only one reduces inflammation
Ibuprofen inhibits cyclooxygenase in peripheral tissue, reducing the prostaglandins that drive swelling, redness and sensitisation of pain fibres. Paracetamol has little peripheral COX activity at therapeutic concentrations and appears to act mainly within the central nervous system. That is why paracetamol relieves the pain of an inflamed joint without reducing the inflammation itself.
Why paracetamol overdose is a liver problem
Most paracetamol is conjugated safely, with a small fraction oxidised by CYP2E1 to NAPQI, a reactive metabolite neutralised by glutathione. In overdose the conjugation pathways saturate, more NAPQI is produced, glutathione is exhausted and the metabolite binds hepatocyte proteins directly. Acetylcysteine works by replenishing glutathione, which is why timing matters so much.
Why they are often combined
Because the mechanisms are different and largely independent, combining them produces better analgesia than increasing either alone, without adding the other drug risk. This is a genuine example of rational combination rather than marketing, and it is the standard approach in multimodal analgesia.
Which one would the question pick?
Exams rarely ask what a drug does. They describe a patient and ask which of the two you would choose, so the scenarios below matter more than either drug monograph.
| Scenario | Pick | Why |
|---|---|---|
| Simple fever or headache | Paracetamol | Effective, with minimal organ risk at correct doses. |
| Inflammatory pain such as sprain or arthritis | Ibuprofen | Peripheral COX inhibition reduces the inflammation driving the pain. |
| Peptic ulcer disease or renal impairment | Paracetamol | Avoids the gastric and renal effects of COX inhibition. |
| Significant liver disease or heavy alcohol use | Ibuprofen, with caution | Paracetamol metabolism and glutathione reserve may be compromised. |
Traps that catch people on this pair
Calling paracetamol an NSAID
It is not meaningfully anti-inflammatory and does not share the gastric or renal risks, so grouping it with NSAIDs produces wrong answers.
Assuming a normal early paracetamol level is reassuring
Hepatic injury develops over days, and the patient can look well while it is under way. Treatment decisions follow the timed nomogram, not how the patient appears.
Common questions
What is the difference between paracetamol and ibuprofen?
Ibuprofen inhibits COX peripherally, so it is anti-inflammatory and carries gastric and renal risk. Paracetamol acts largely centrally, is not meaningfully anti-inflammatory, and is safe at therapeutic doses but causes hepatic necrosis in overdose through a toxic metabolite.
Is paracetamol an anti-inflammatory?
No. It relieves pain and fever but has little peripheral cyclooxygenase activity at therapeutic doses, so it does not meaningfully reduce inflammation the way an NSAID does.
Why is paracetamol overdose dangerous?
The safe conjugation pathways saturate, so more of the drug is oxidised to NAPQI, a reactive metabolite. Once glutathione is exhausted, NAPQI binds liver cell proteins and causes hepatic necrosis.
Can you take paracetamol and ibuprofen together?
They work by different mechanisms, so combining them gives better analgesia than increasing either alone. Doses and any contraindications for each drug still apply separately.
Go deeper on the mechanism
A comparison only sticks once the shared mechanism underneath it does, because what separates two drugs is always a variation on something they have in common.
- Cardiovascular pharmacology questions — test the distinction under time
- When to avoid NSAIDs
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Study aid only. This page is written for learning and examination practice. It is not medical advice, not clinical decision support, and must never be used to make a decision about a real patient. Always verify against your local formulary, the product literature and a qualified pharmacist. See our medical disclaimer.
Two drugs, one property apart.
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