Ibuprofen: Non-steroidal anti-inflammatory drug (NSAID), a propionic acid derivative

What it is

Ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) from the propionic acid family. It was synthesised in 1961 by Stewart Adams at the Boots laboratories and approved in the UK in 1969.

Today it is one of the most widely used medicines in the world. In Spain it is available without a prescription at 400 mg (for adults) and on prescription at 600–800 mg. It also comes in topical (gel), paediatric (suspension) and intravenous forms for hospital use.

It acts on pain, fever and inflammation at the same time, which makes it very versatile at the counter.

How it acts on the body

Ibuprofen inhibits the COX (cyclo-oxygenase) enzyme, which exists in two forms with different roles:

COX-1 → produces prostaglandins that protect the stomach and regulates platelet aggregation. Ibuprofen inhibits it → which is why it irritates the stomach.
COX-2 → produces the prostaglandins of inflammation, pain and fever. Ibuprofen inhibits it → which is why it relieves pain, inflammation and fever.
Because it inhibits both COX forms without selectivity, it is analgesic + anti-inflammatory + antipyretic, but also carries a gastric risk.
Unlike paracetamol (which acts mainly in the central nervous system), ibuprofen acts where the inflammation is: it works better for pain with an inflammatory component.

At the counter

When to recommend it

Mild to moderate pain with an inflammatory component: muscular, joint, dental, menstrual
Tension-type headache in adults without contraindications
Fever in adults when paracetamol is not enough or the patient does not tolerate it
Mild post-operative pain (after a tooth extraction, etc.) combined with paracetamol
Primary dysmenorrhoea: the first choice because of its anti-inflammatory effect in the pelvis

When not to

Pregnancy: avoid from week 20 and contraindicated in the third trimester (oligohydramnios, premature closure of the ductus arteriosus)
Moderate to severe kidney failure (it reduces renal blood flow and can trigger a crisis)
Heart failure or significant peripheral oedema
Poorly controlled high blood pressure (it retains sodium and water)
Active peptic ulcer or a recent history of gastrointestinal bleeding
Known allergy to NSAIDs or aspirin (aspirin-induced asthma = absolute contraindication)
Babies under 3 months
Combining with other NSAIDs (adds no benefit, only adds risk)

What to say at the counter. If the patient has a sensitive stomach, always advise taking it with food and offer omeprazole. The line at the counter: 'With ibuprofen it is always a good idea to protect your stomach — would you like me to add an omeprazole?'

Warnings

Important PREGNANCY: avoid from week 20 (it can reduce the amniotic fluid) and contraindicated in the third trimester, when it can close the fetal ductus arteriosus prematurely. Always ask whether the patient is pregnant.
Important CHICKENPOX: ibuprofen in children with chickenpox has been linked to severe streptococcal skin infections (necrotising fasciitis). Use paracetamol for fever in chickenpox.
Caution HYPERTENSION: it blunts the effect of blood pressure medicines (especially ACE inhibitors and ARBs) and can raise blood pressure even in controlled patients.
Caution ANTICOAGULANTS: it increases the risk of bleeding with warfarin, acenocoumarol and the direct oral anticoagulants (rivaroxaban, apixaban). Prefer paracetamol.
Caution OLDER AGE: over 65 the gastrointestinal and kidney risk is significantly higher. Always with gastric protection, and consider paracetamol as an alternative.
Caution CORTICOSTEROIDS: NSAID + corticosteroid multiplies the risk of ulcer and gastrointestinal bleeding. Always add omeprazole if this combination is used.
Worth knowing ALCOHOL: regular alcohol use increases the risk of gastrointestinal bleeding.

Pharmacokinetics

Absorption: Oral: rapid and almost complete absorption (80–90%) from the gastrointestinal tract. Peak plasma level at 60–90 minutes. The lysine and arginine salts are absorbed faster (30–45 min) because they are more water-soluble.
Distribution: High plasma protein binding (99%), mainly to albumin. Small volume of distribution: it stays in plasma and well-perfused tissues. It crosses the placenta and passes into breast milk in small amounts.
Metabolism: Almost entirely hepatic, mainly via CYP2C9. It produces inactive metabolites. No significant first-pass metabolism. It interacts with other drugs that use CYP2C9 (warfarin, phenytoin).
Elimination: Renal, mostly as conjugated metabolites. Half-life: 1.8–2 hours (short → it has to be repeated every 6–8 hours to keep levels up). It accumulates in kidney failure → use with caution.

Ibuprofen vs paracetamol

Aspect	Ibuprofen	Paracetamol
Mechanism	Inhibits COX-1 and COX-2 peripherally	Inhibits COX in the CNS (mechanism not fully understood)
Pain relief	Good, especially for inflammatory pain	Good, especially for headache and pain without inflammation
Anti-inflammatory	Yes, a real effect	Minimal or none
Antipyretic	Yes	Yes (similar effect)
Gastric risk	Moderate (inhibits COX-1)	Minimal
Kidney risk	Moderate (reduces renal blood flow)	Minimal at normal doses
Liver risk	Minimal at normal doses	High in overdose or with alcohol
Pregnancy	Avoid from week 20; contraindicated in the third trimester	First choice
Children with chickenpox	Contraindicated	First choice
Patient with hypertension	Caution (retains sodium)	Preferable

The practical counter rule: if there is inflammation → ibuprofen. If there is no inflammation, or there is pregnancy, chickenpox, hypertension, compromised kidneys or anticoagulants → paracetamol. When in doubt, paracetamol is the safest for most people.

Self-assessment

Three questions. When you check your answers you will see the explanation for each one.

A woman who is 28 weeks pregnant asks for ibuprofen for a headache. What do you do? Give her ibuprofen 400 mg because it is the low, non-prescription dose Explain that ibuprofen should be avoided from week 20 of pregnancy and recommend paracetamol Tell her to see her obstetrician before taking anything
A 6-year-old child has a fever with chickenpox. The mother asks for children's ibuprofen. What do you do? Give it to her because it is the right paediatric dose Tell her to see the paediatrician before giving any fever medicine Explain that ibuprofen is contraindicated in chickenpox and that she should use paracetamol
Why does ibuprofen work better than paracetamol for period pain? Because it is more potent in general Because it acts directly on the prostaglandins that cause uterine contraction and pelvic inflammation Because it is absorbed faster

Training content. It does not replace the summary of product characteristics or clinical judgement.

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