Mefenamic acid

Mefenamic acid
ATC Code M01AG01
Formula C15H15NO2
Molar Mass (g·mol−1) 241,29
Physical State solid
Melting Point (°C) 230–231
PKS Value 4,2
CAS Number 61-68-7
PUB Number 4044
Drugbank ID DB00784
Solubility practically insoluble in water, sparingly soluble in ethanol, soluble in dilute alkali hydroxide solutions


Mefenamic acid is an active substance of the group of non-steroidal anti-inflammatory drugs (NSAIDs). It is used for the symptomatic treatment of joint and muscle pain, rheumatic diseases, menstrual pain, swelling and inflammation after surgery and for spinal pain. In rare cases, it can also be used to reduce fever. The main dosage forms available are capsules and tablets.

Mefenamic acid is available without prescription in Switzerland and Austria. In Germany, mefenamic acid is not approved.



Mefenamic acid is a derivative of anthranilic acid with antipyretic, analgesic and antiphlogistic properties. It binds to both cyclooxygenase 1 and 2 enzymes, preventing the synthesis of prostaglandins and thromboxanes. Prostaglandins play an important role in the development of pain and inflammatory processes in the body. If fewer prostaglandins are now produced, there is a reduction in pain and fever.


Mefenamic acid is rapidly absorbed into the circulation after oral administration and approximately 90% is bound by plasma proteins. The plasma half-life is 2 hours. The drug is degraded by the liver enzyme CYP2C9 to 3-hydroxymethyl-mefenamic acid and is then conjugated to the substance glucuronic acid. Mefenamic acid is preferentially excreted in the urine, 20% of the substance is excreted in the stool.


Possible overdose symptoms are severe abdominal pain, discoloration of stools, tinnitus, muscle weakness, changes in heart rate, shallow breathing, confusion, headache, and loss of consciousness.

Taking it with alcohol can cause serious adverse side effects.

Common side effects

The most common adverse reactions include nausea and vomiting, gastrointestinal distress, loss of appetite, and various blood count changes.

Toxicological Data:

Oral, rat LD50: 740 mg/kg.

Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter ist Autor zu pharmazeutischen Themen in der Medizin-Redaktion von Medikamio. Er befindet sich im letzten Semester seines Pharmaziestudiums an der Universität Wien und liebt das wissenschaftliche Arbeiten im Bereich der Naturwissenschaften.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer ist seit 2020 freie Autorin bei Medikamio und studierte Pharmazie an der Universität Wien. Sie arbeitet als Apothekerin in Wien und ihre Leidenschaft sind pflanzliche Arzneimittel und deren Wirkung.

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