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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties, primarily through the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Treatment of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain and continuing for the duration of the symptoms.
* **Maximum Dose:** 1500 mg per day. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age.
## Dose Adjustments
No dose adjustment is typically required for renal or hepatic impairment, but caution is advised. Use the lowest effective dose for the shortest duration necessary.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or ulceration.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, dizziness, headache, rash.
* **Serious:**
* **GI:** GI bleeding, ulceration, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Renal:** Renal papillary necrosis, interstitial nephritis, renal failure.
* **Hepatic:** Hepatitis, jaundice.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Other:** Bronchospasm (especially in aspirin-sensitive asthmatics).
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of GI toxicity and other adverse effects.
* **Diuretics and Antihypertensives:** Reduced efficacy; increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* **GI symptoms:** Monitor for signs and symptoms of GI bleeding and ulceration.
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Monitor LFTs, especially with long-term use or in patients with hepatic impairment.
* **Blood pressure:** Monitor for potential increases.
* **Signs of hypersensitivity reactions.**
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Use the lowest effective dose for the shortest duration necessary to minimize the risk of serious cardiovascular, GI, and renal adverse events.
* Discontinue at the first sign of rash, allergic reaction, or GI bleeding.
* Consider alternative analgesics if pain is severe or chronic.
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**Disclaimer:** This information is intended for clinical use and is not a substitute for professional medical advice. Always verify current prescribing information with the official drug product labeling and relevant clinical guidelines.
