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# Ibuprofen

A widely used NSAID for pain, fever and inflammation. It reversibly blocks both cyclooxygenases.

Updated 2026-11-01

- Class: [Nonsteroidal anti-inflammatory drugs (NSAIDs)](https://durgical.com/en/pharmacology/classes/nonsteroidal-anti-inflammatory-drugs/)
- Enzyme: Cyclooxygenase 1 and 2 (COX-1/COX-2)
- ATC code: M01AE01
- WHO Model List of Essential Medicines

✂**Cyclooxygenase 1 and 2 (COX-1/COX-2)**Ibuprofen

ⓘ The figure shows ibuprofen in the channel of mouse COX-2, which keeps the same site as the human enzyme.

**Target in 3D:** Cyclooxygenase 1 and 2 (COX-1/COX-2). PDB structure 4PH9 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/4PH9) · Drag to rotate · pinch to zoom

## Mechanism of action

Ibuprofen, a propionic acid derivative, reversibly occupies the channel of COX-1 and COX-2 and keeps arachidonic acid from reaching the catalytic site. Prostaglandins that sensitize nociceptors, raise the thermal set point and sustain inflammation fall. Because it lets go of the enzyme, its antiplatelet effect is mild and short-lived.

- Reversibly occupies the COX-1 and COX-2 channel
- Arachidonic acid is not converted to prostaglandin H2
- Less PGE2: calmer nociceptors and a lower thermal set point
- Relief of pain, fever and inflammation

## Pharmacokinetics

**Absorption**
Well absorbed by mouth.

**Distribution**
Almost completely bound to albumin.

**Metabolism**
Liver, mainly CYP2C9, to inactive metabolites.

**Elimination**
Kidney, as metabolites.

**Half-life**
About 2 hours; longer in liver disease.

## Indications

- Primary dysmenorrhea [Dysmenorrhoea →](https://durgical.com/en/conditions/dysmenorrhoea/)
- Rheumatoid arthritis (symptom control) [Rheumatoid arthritis →](https://durgical.com/en/conditions/rheumatoid-arthritis/)
- Acute gout flare [Gout →](https://durgical.com/en/conditions/gout/)
- Migraine attacks [Migraine →](https://durgical.com/en/conditions/migraine/)
- Mild to moderate pain and fever; closure of a patent ductus arteriosus in newborns

## Adverse effects

### Common

- Dyspepsia, nausea and abdominal pain
- Fluid retention and edema
- Raised blood pressure

### Serious (rare, important)

- Gastrointestinal ulcer and bleeding
- Acute kidney injury
- Myocardial infarction and stroke with prolonged use
- Bronchospasm in NSAID-sensitive people

## Contraindications

- The period right before or after coronary artery bypass surgery
- Active peptic ulcer or gastrointestinal bleeding
- Severe kidney failure or severe heart failure
- Pregnancy from week 20 onward, unless specialist-directed
- Asthma or urticaria triggered by NSAIDs

## Key interactions

**Aspirin**
Can block its antiplatelet effect if it occupies COX-1 first.

**ACE inhibitors or ARBs with diuretics**
Higher risk of acute kidney injury and a weaker antihypertensive effect.

**Anticoagulants and SSRIs**
More risk of gastrointestinal bleeding.

**Lithium and methotrexate**
Reduced renal clearance and risk of toxicity.

## What is monitored

- Blood pressure and kidney function with prolonged use
- Signs of gastrointestinal bleeding

## Memory aid

Ibuprofen is a short-stay tenant: it occupies COX for a few hours and moves out. Aspirin, by contrast, changes the lock.

## Test yourself

Think of the answer, then tap the question to see it.

## How does COX inhibition by ibuprofen differ from that by aspirin?

Ibuprofen binds reversibly and competitively, so its effect lasts only while the drug stays in the site; aspirin acetylates the enzyme irreversibly.

## Why do NSAIDs such as ibuprofen relieve primary dysmenorrhea?

The pain comes mainly from excess endometrial prostaglandins, which drive strong uterine contractions and ischemia; lowering them reduces contractions and pain.

## Which drug combination with ibuprofen raises the risk of acute kidney injury?

An ACE inhibitor or ARB plus a diuretic. The NSAID constricts the afferent arteriole, the ACE inhibitor or ARB dilates the efferent one and the diuretic lowers volume: filtration falls.

## Why is ibuprofen contraindicated from week 20 of pregnancy?

Fetal prostaglandins support fetal kidney function and keep the ductus arteriosus open; inhibiting them can cause oligohydramnios and premature ductal closure.

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## Related drugs

- [Acetylsalicylic acid](https://durgical.com/en/pharmacology/acetylsalicylic-acid/)
- [Celecoxib](https://durgical.com/en/pharmacology/celecoxib/)

## Related conditions

- [Dysmenorrhoea](https://durgical.com/en/conditions/dysmenorrhoea/)
- [Rheumatoid arthritis](https://durgical.com/en/conditions/rheumatoid-arthritis/)
- [Gout](https://durgical.com/en/conditions/gout/)
- [Migraine](https://durgical.com/en/conditions/migraine/)

[← Back to the class: Nonsteroidal anti-inflammatory drugs (NSAIDs)](https://durgical.com/en/pharmacology/classes/nonsteroidal-anti-inflammatory-drugs/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Ibuprofen: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682159.html) (MedlinePlus (U.S. National Library of Medicine), 2023); [Ibuprofen, (+-)-](https://pubchem.ncbi.nlm.nih.gov/compound/3672#section=Metabolism-Metabolites) (PubChem (NCBI), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=M01AE01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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