Drug information of Mefenamic acid

Mefenamic acid

Drug group:

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID). Mefenamic acid works by reducing hormones that cause inflammation and pain in the body. Mefenamic acid is used short-term (7 days or less) to treat mild to moderate pain in adults and children who are at least 14 years old. Mefenamic acid is also used to treat menstrual pain.

Mechanism of effect

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 has analgesic, anti-inflammatory, and antipyretic properties.


Mefenamic Acid is rapidly absorbed after oral administration. Peak plasma levels are attained in 2 to 4 hours and the elimination half-life approximates 2 hours. Mefenamic Acid has been reported as being greater than 90% bound to albumin. Mefenamic Acid is metabolized by cytochrome P450 enzyme CYP2C9 to 3-hydroxymethyl Mefenamic Acid (Metabolite I) Approximately fifty-two percent of a Mefenamic Acid dose is excreted into the urine. The fecal route of elimination accounts for up to 20% of the dose


Usual Adult Dose for Pain
Initial dose: 500 mg orally once
Following initial dose: 250 mg orally every 6 hours as needed
Duration of therapy: Usually not to exceed 1 week
Usual Adult Dose for Dysmenorrhea
Initial dose: 500 mg orally once
Following initial dose: 250 mg orally every 6 hours as needed
Duration of therapy: 2 to 3 days


1-Nonsteroidal anti-inflammatory drugs (NSAIDs) cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may occur early in treatment and may increase with duration of use.
2-Mefenamic Acid is contraindicated in the setting of coronary artery bypass graft (CABG) surgery
3-NSAIDs cause an increased risk of serious gastrointestinal (GI) adverse events including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events can occur at any time during use and without warning symptoms.
4-Elderly patients and patients with a prior history of peptic ulcer disease and/or GI bleeding are at greater risk for serious GI events.

Points of recommendation

1-Avoid alcohol.
2-Take with food.
3-Advise patients to report symptoms of ulcerations and bleeding, including epigastric pain, dyspepsia, melena, and hematemesis to their healthcare provider.
4-Inform pregnant women to avoid use of Mefenamic Acid and other NSAIDs starting at 30 weeks gestation because of the risk of the premature closure of the fetal ductus arteriosus

Pregnancy level


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