ATC Code G02CC02, M01AE02, M02AA12
Formula C14H14O3
Molar Mass (g·mol−1) 230,26
Physical State solid
Melting Point (°C) 152
PKS Value 4.15
CAS Number 22204-53-1
PUB Number 156391
Drugbank ID DB00788
Solubility sparingly soluble in water


Naproxen is a non-steroidal anti-inflammatory drug (NSAID) used to treat pain, menstrual cramps, inflammatory conditions such as rheumatoid arthritis, and fever. It is taken orally and is available in immediate-release and delayed-release formulations.



Naproxen acts as a non-selective coxib through reversible inhibition of both COX-1 and COX-2 enzymes. This results in inhibition of prostaglandin synthesis. Prostaglandins act as signaling molecules in the body and induce inflammation, fever, and pain. Thus, by inhibiting COX-1/2, naproxen induces anti-inflammatory, antipyretic, and analgesic effects.


Naproxen is highly protein-bound, with >99% of the drug bound to albumin (major plasma protein) at therapeutic concentrations. Naproxen is a substrate of CYP1A2 and CYP2C9. It is largely metabolized in the liver to 6-O-desmethylnaproxen, and both naproxen and the desmethyl metabolite are further metabolized to their respective acylglucuronide-conjugated metabolites. After metabolization, a majority of the given dose is excreted in the urine.

Drug Interactions

Naproxen may interact with antidepressants, lithium, methotrexate, probenecid, warfarin and other blood thinners, heart or blood pressure medications, including diuretics, or steroid medications such as prednisone.

NSAR wie Naproxen können die Wirksamkeit von SSRI-Antidepressiva beeinträchtigen und vermindern sowie das Blutungsrisiko erhöhen, das größer ist als das individuelle Blutungsrisiko der beiden Wirkstoffklassen, wenn sie zusammen eingenommen werden. Naproxen ist in Gegenwart von SSRIs nicht kontraindiziert, allerdings sollte die gleichzeitige Anwendung der Medikamente mit Vorsicht erfolgen.


Side effects

Common side effects include:

  • Dizziness
  • Headache
  • bruising
  • allergic reactions
  • heartburn
  • stomach pain.

Serious side effects include increased risk of heart disease, stroke, gastrointestinal bleeding, and stomach ulcers. The risk of heart disease may be lower than with other NSAIDs. It is not recommended in people with kidney problems. Use is not recommended in the third trimester of pregnancy.

Toxicological Data

LD50 (rat, oral): 248 mg-kg-1


  • Drugbank
  • PubChem
  • Aktories, Förstermann, Hofmann, Starke: Allgemeine und spezielle Pharmakologie und Toxikologie, Elsvier, 2017

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All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.

Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter is a writer on pharmaceutical topics in Medikamio's medical editorial team. He is in the last semester of his pharmacy studies at the University of Vienna and loves scientific work in the field of natural sciences.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer has been a freelance writer for Medikamio since 2020 and studied pharmacy at the University of Vienna. She works as a pharmacist in Vienna and her passion is herbal medicines and their effects.

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