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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It acts by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 to 8 hours as needed. Do not exceed 1500 mg in a 24-hour period.
* **Dysmenorrhea:** 500 mg every 6 to 8 hours, initiated at the onset of bleeding and associated pain. Continue for up to 3 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to a lack of established safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dosage adjustments are established, but clearance may be reduced in severe impairment.
* **Hepatic Impairment:** Use with caution. No specific dosage adjustments are established, but NSAIDs can affect liver function.
## 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).
* Severe heart failure.
* Significant renal or hepatic impairment.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal papillary necrosis, interstitial nephritis, renal failure; hepatic toxicity; cardiovascular thrombotic events; exacerbation of asthma; hypersensitivity reactions; Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
* **Lithium:** Mefenamic acid can decrease lithium clearance, leading to increased lithium levels and potential toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Diuretics and Antihypertensives:** NSAIDs may blunt the effect of these agents and increase the risk of renal impairment.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding or ulceration.
* Renal function (BUN, creatinine) especially in patients with risk factors.
* Liver function (LFTs) if therapy is prolonged or in patients with pre-existing liver disease.
* Blood pressure.
* Signs of hypersensitivity or allergic reactions.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* It is intended for short-term use only (typically not exceeding 7 days for pain).
* Monitor for fluid retention and edema, especially in patients with heart failure or hypertension.
* Discontinue if any signs of serious adverse events occur, particularly gastrointestinal bleeding, renal dysfunction, or hepatic impairment.
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*This information is intended for healthcare professionals and does not substitute for comprehensive prescribing information. Always consult the most current drug monograph and institutional protocols for complete details before prescribing.*
