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# Naproxen

A long-acting non-selective NSAID used in arthritis, acute gout and dysmenorrhoea. It can interfere with the antiplatelet effect of acetylsalicylic acid.

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: M01AE02

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

ⓘ The figure shows naproxen 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 3NT1 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3NT1) · Drag to rotate · pinch to zoom

## Mechanism of action

Naproxen, a propionic acid derivative like ibuprofen, reversibly inhibits COX-1 and COX-2 and lowers the prostaglandins of inflammation, pain and fever. Its long half-life means that in some people platelet inhibition lasts through the whole dosing interval.

- Reversibly occupies the channel of COX-1 and COX-2
- Prostaglandin synthesis falls
- Less inflammation, pain and fever
- Its long half-life sustains the effect between doses

## Pharmacokinetics

**Absorption**
Rapid and nearly complete oral absorption.

**Distribution**
Highly protein bound, saturating at high doses; the free fraction rises in older adults.

**Metabolism**
Liver to 6-O-desmethylnaproxen; both are conjugated as acyl glucuronides.

**Elimination**
Almost all in the urine, as conjugates.

**Half-life**
Long: about 12 to 17 hours.

## Indications

- Rheumatoid arthritis [Rheumatoid arthritis →](https://durgical.com/en/conditions/rheumatoid-arthritis/)
- Osteoarthritis [Knee Osteoarthritis →](https://durgical.com/en/conditions/knee-osteoarthritis/)
- Ankylosing spondylitis [Ankylosing spondylitis →](https://durgical.com/en/conditions/ankylosing-spondylitis/)
- Acute gout [Gout →](https://durgical.com/en/conditions/gout/)
- Primary dysmenorrhoea [Dysmenorrhoea →](https://durgical.com/en/conditions/dysmenorrhoea/)
- Tendinitis, bursitis and pain in general

## Adverse effects

### Common

- Constipation and gas
- Headache, dizziness and drowsiness
- Trouble sleeping
- Ringing in the ears

### Serious (rare, important)

- Cardiovascular thrombotic events (heart attack, stroke), which can appear early and increase with duration of use
- Gastrointestinal ulcer, bleeding and perforation, sometimes without warning symptoms
- Acute kidney injury and hyperkalaemia
- Anaphylaxis and serious skin reactions

## Contraindications

- Hypersensitivity to the drug
- Asthma, urticaria or another allergic reaction after acetylsalicylic acid or another NSAID
- The setting of coronary artery bypass graft (CABG) surgery

## Key interactions

**Low-dose acetylsalicylic acid**
Naproxen can interfere with its antiplatelet effect, above all when taken before the acetylsalicylic acid.

**Anticoagulants (warfarin), antiplatelet agents, SSRIs and SNRIs**
Add to the risk of bleeding.

**ACE inhibitors, ARBs and diuretics**
Blunt their antihypertensive and diuretic effect; in older or volume-depleted patients they can precipitate acute kidney injury.

**Lithium**
Raise its blood levels by lowering renal clearance.

**Methotrexate**
Raise the risk of methotrexate toxicity (neutropenia, thrombocytopenia, kidney damage).

## What is monitored

- Signs of gastrointestinal bleeding
- Kidney function and potassium
- Blood pressure and oedema

## Administration and safety

- There are naproxen and naproxen sodium; the two are not added together, nor with other over-the-counter NSAIDs.
- Over-the-counter naproxen may be taken with food or milk to prevent nausea.

## Nursing care

- Before starting: history of ulcer, bleeding, kidney or cardiovascular disease, or asthma with NSAIDs.
- Watch for black stools, vomiting blood, abdominal pain and signs of anaemia.
- Watch blood pressure, oedema, urine output and creatinine, above all in older patients or those on diuretics.
- In patients on acetylsalicylic acid for cardiovascular protection, report the possible effect of naproxen on its antiplatelet action.

## Pregnancy and breastfeeding

From about week 20 it can cause fetal kidney dysfunction with oligohydramnios, and from about week 30 premature closure of the ductus arteriosus; so use is limited between those weeks and avoided late in pregnancy.

## Memory aid

NAPROXEN = a long NAP: the long half-life means fewer doses a day. But if it goes before aspirin, it «steals» the platelet's seat.

## Test yourself

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

## What practical advantage does naproxen's long half-life give?

It keeps working with fewer daily doses than ibuprofen and, in some people, sustains platelet inhibition through the whole interval.

## How does naproxen interact with low-dose acetylsalicylic acid?

It can occupy platelet COX-1 and get in the way of acetylation by acetylsalicylic acid, reducing its antiplatelet effect, above all when taken first.

## Why can naproxen be more toxic in older adults?

Because its free fraction in plasma rises, which contributes to more gastrointestinal adverse effects.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/naproxen/)

## Related drugs

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

## Related conditions

- [Rheumatoid arthritis](https://durgical.com/en/conditions/rheumatoid-arthritis/)
- [Knee Osteoarthritis](https://durgical.com/en/conditions/knee-osteoarthritis/)
- [Ankylosing spondylitis](https://durgical.com/en/conditions/ankylosing-spondylitis/)
- [Gout](https://durgical.com/en/conditions/gout/)
- [Dysmenorrhoea](https://durgical.com/en/conditions/dysmenorrhoea/)

[← 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: [Naproxen: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a681029.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [NAPROXEN tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2718e0b7-1ce6-457e-bee9-11b634dfd353) (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 42 (McGraw Hill, 2023); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=M01AE02) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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