Drug Groups

approved

Description

A non-steroidal anti-inflammatory agent with analgesic, anti-inflammatory, and antipyretic properties. It is an inhibitor of cyclooxygenase. [PubChem]

Indication

For the treatment of rheumatoid arthritis, osteoarthritis, dysmenorrhea, and mild to moderate pain, inflammation, and fever.

Pharmacology

Mefenamic acid, an anthranilic acid derivative, is a member of the fenamate group of nonsteroidal anti-inflammatory drugs (NSAIDs). It exhibits anti-inflammatory, analgesic, and antipyretic activities. Similar to other NSAIDs, mefenamic acid inhibits prostaglandin synthetase.

Toxicity

Oral, rat LD₅₀: 740 mg/kg. Symptoms of overdose may include severe stomach pain, coffee ground-like vomit, dark stool, ringing in the ears, change in amount of urine, unusually fast or slow heartbeat, muscle weakness, slow or shallow breathing, confusion, severe headache or loss of consciousness.

Affected Organisms

Biotransformation

Mefenamic acid undergoes metabolism by CYP2C9 to 3-hydroxymethyl mefenamic acid, and further oxidation to a 3-carboxymefenamic acid may occur. The activity of these metabolites has not been studied. Mefenamic acid is also glucuronidated directly.

Absorption

Mefenamic acid is rapidly absorbed after oral administration.

Half Life

2 hours

Protein Binding

90%

Elimination

The fecal route of elimination accounts for up to 20% of the dose, mainly in the form of unconjugated 3-carboxymefenamic acid.3 The elimination half-life of mefenamic acid is approximately two hours. Mefenamic acid, its metabolites and conjugates are primarily excreted by the kidneys. Both renal and hepatic excretion are significant pathways of elimination.

Distribution

* 1.06 L/kg [Normal Healthy Adults (18-45 yr)]

Clearance

* Oral cl=21.23 L/hr [Healthy adults (18-45 yrs)]

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