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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain.
## Primary Indications
* Pain associated with osteoarthritis
* Pain associated with rheumatoid arthritis
* Menstrual pain (dysmenorrhea)
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum daily dose:** 1500 mg for general pain. For dysmenorrhea, the maximum daily dose is 750 mg for the first day, followed by 500 mg daily thereafter.
* **Duration of use:** Typically limited to 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age. Specific pediatric dosing is not well-established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease (active or history of).
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Diarrhea, nausea, vomiting, abdominal pain, constipation.
* Central Nervous System: Dizziness, headache, drowsiness.
* Other: Rash, pruritus, tinnitus.
Serious adverse effects include:
* Gastrointestinal bleeding, ulceration, and perforation.
* Cardiovascular thrombotic events (MI, stroke).
* Renal toxicity.
* Hepatic toxicity.
* Hypersensitivity reactions.
* Hematologic effects.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Lithium:** Increased lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
* **Diuretics and Antihypertensives:** Reduced efficacy; increased risk of renal toxicity.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor blood pressure.
* Monitor for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to reduce gastrointestinal upset.
* Due to the risk of diarrhea, it is generally recommended for short-term use only.
* It is a potent NSAID and carries similar risks to other agents in its class.
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*This information is intended for clinical use and does not replace a thorough review of the current prescribing information or local protocols. Always verify current drug information before making clinical decisions.*
