Paracetamol versus NSAIDs
Paracetamol relieves pain and lowers fever (it is analgesic and antipyretic) but has negligible anti-inflammatory action, unlike NSAIDs (non-steroidal anti-inflammatory drugs such as ibuprofen).
Remember
Paracetamol is thought to act mainly in the central nervous system (the brain and spinal cord), which is part of the reason it relieves pain and fever but has negligible anti-inflammatory action, and it has little effect on the stomach, kidneys or platelets at usual doses.
Memory aid
paracetamol works mainly "upstairs" in the brain and spinal cord, whereas NSAIDs work mainly "on site" where tissue is injured
Think of paracetamol as working upstairs in the brain and spinal cord, and NSAIDs working on site where tissue is injured.
Cyclooxygenase (COX) enzymes make prostaglandins, local chemical messengers, and these drive pain, fever and inflammation. NSAIDs block COX throughout the body. They reduce swelling, but carry stomach, kidney and bleeding risks.
Paracetamol is different. The exact mechanism is still not fully understood. The leading hypotheses are that it inhibits a CNS-specific COX isoform (a variant form of the enzyme, found in the brain and spinal cord) and that it acts on the descending pain pathways (nerve routes from the brain that dampen incoming pain signals).
Paracetamol is thought to act mainly in the central nervous system, which is part of the reason it relieves pain and fever but has negligible anti-inflammatory action. At usual doses it has little effect on the stomach, kidneys or platelets (small cell fragments that start clotting), which is the main safety advantage over NSAIDs.
In someone with a past peptic ulcer (an ulcer in the stomach or duodenum), paracetamol is a sensible simple painkiller, because NSAIDs remove the stomach's protective prostaglandins. In pregnancy, the NHS describes paracetamol as usually the best painkiller, and ibuprofen is best avoided unless a doctor or pharmacist advises it. The trade-off is that it will ease the pain of a sprain but not the swelling.
Key facts
- Actions
- Paracetamol is analgesic and antipyretic, with negligible anti-inflammatory action.
- Site of action
- It acts mainly in the central nervous system, although the exact mechanism is still not fully understood.
- Safety profile
- At usual doses it has little effect on the stomach, kidneys or platelets, which are the usual NSAID problems.
- Classification
- Paracetamol is not an NSAID.
- Aspirin contrast
- Aspirin alone among the NSAIDs has a clinically useful antiplatelet effect, meaning it makes platelets less sticky.
- Pregnancy
- The NHS describes paracetamol as usually the best painkiller in pregnancy, and ibuprofen is best avoided unless a doctor or pharmacist advises it.
Exam traps
- Paracetamol does not strongly block COX in peripheral tissue, because that is what NSAIDs such as ibuprofen do, and so it has minimal anti-inflammatory activity.
- Paracetamol does not irreversibly block platelet COX, because that is the property of aspirin; at usual doses it has little effect on platelets.
- Stomach ulceration is not a typical feature of paracetamol, because at usual doses it has little effect on the stomach's prostaglandins; ulceration is a classic NSAID problem.
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