Mefenamic Acid

What it is and how it works

Mechanism of Action Mefenamic acid has analgesic, anti-inflammatory, and antipyretic properties. The mechanism of action of mefenamic acid, like that of other NSAIDs, is not completely understood but involves inhibition of cyclooxygenase (COX-1 and COX-2). Mefenamic acid is a potent inhibitor of prostaglandin synthesis in vitro. Mefenamic acid concentrations reached during therapy have produced in vivo effects. Prostaglandins sensitize afferent nerves and potentiate the action of bradykinin in inducing pain in animal models. Prostaglandins are mediators of inflammation.

Mechanism class: Cyclooxygenase Inhibitors

Indications

Mefenamic acid capsules are a nonsteroidal anti-inflammatory drug indicated for: For management of mild to moderate pain in patient 14 years of age and older, when therapy will not exceed one week (7 days). For treatment of primary dysmenorrhea. Mild to Moderate Pain Mefenamic acid capsules are indicated for management of mild to moderate pain in adults and pediatric patients 14 years of age and older, when therapy will not exceed one week (7 days). Dysmenorrhea Mefenamic acid capsules are indicated for treatment of primary dysmenorrhea.

Dosage and administration (summary)

Adults and adolescents 14 years of age and older: 500 mg given orally as an initial dose followed by 250 mg every 6 hours as needed For the treatment of primary dysmenorrhea: 500 mg given orally as an initial dose followed by 250 mg every 6 hours Important Dosage and Administration Information Carefully consider the potential benefits and risks of mefenamic acid capsules and other treatment options before deciding to use mefenamic acid capsules. Use the lowest effective dose for the shortest duration consistent with individual patient treatment goals .

Contraindications

Mefenamic acid is contraindicated in the following patients: Known hypersensitivity (e.g., anaphylactic reactions and serious skin reactions) to mefenamic acid or any components of the drug product . History of asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. Severe, sometimes fatal, anaphylactic reactions to NSAIDs have been reported in such patients . In the setting of coronary artery bypass graft (CABG) surgery .

Warnings and precautions

Hepatotoxicity : Inform patients of warning signs and symptoms of hepatotoxicity. Discontinue if abnormal liver tests persist or worsen or if clinical signs and symptoms of liver disease develop. Hypertension : Patients taking some antihypertensive medications may have impaired response to these therapies when taking NSAIDs. Monitor blood pressure. ( 5.4 , 7 ) Heart Failure and Edema : Avoid use of mefenamic acid in patients with severe heart failure unless benefits are expected to outweigh risk of worsening heart failure.

Pregnancy

Pregnancy Risk Summary Use of NSAIDs, including mefenamic acid, can cause premature closure of the fetal ductus arteriosus and fetal renal dysfunction leading to oligohydramnios and, in some cases, neonatal renal impairment.

Storage and supply

How Supplied Mefenamic acid capsules, USP is available as 250 mg yellow-yellow colored size ‘1’ hard gelatin capsule, imprinted with “ML" on cap and "250” on the body in the following presentations: Bottles of 30 count NDC 42571-258-30 Bottles of 100 count NDC 42571-258-01 Dispense in a tight container as defined in the USP.

Source: Mefenamic Acid (Mefenamic Acid) — US FDA prescribing information, 2026-01-12, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.