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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exerts analgesic and anti-inflammatory effects primarily through the inhibition of cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Management of signs and symptoms of rheumatoid arthritis and osteoarthritis.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 4000 mg per day.
* **Rheumatoid Arthritis / Osteoarthritis:** 500 mg three times daily, with food.
## 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. Dosage reduction may be necessary in severe impairment. Mefenamic acid is primarily renally excreted.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* History of aspirin-induced asthma, urticaria, or allergic-type reactions.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Severe renal or hepatic impairment.
* Active gastrointestinal bleeding.
## Adverse Effects
* **Gastrointestinal:** Dyspepsia, nausea, vomiting, diarrhea, abdominal pain, constipation, flatulence, gastric or duodenal ulcers, GI bleeding, perforation.
* **Central Nervous System:** Dizziness, headache, drowsiness.
* **Renal:** Renal toxicity, interstitial nephritis, papillary necrosis, renal failure.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Other:** Rash, pruritus, fluid retention, edema, hypertension.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of GI toxicity and bleeding; concurrent use is generally not recommended.
* **ACE inhibitors and ARBs:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic effect and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Renal function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Monitor LFTs periodically, especially in patients with hepatic impairment.
* **Gastrointestinal symptoms:** Assess for signs and symptoms of GI bleeding or ulceration.
* **Blood pressure:** Monitor for potential increases in blood pressure.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Limit use to the shortest duration necessary due to the risk of serious adverse events, particularly GI bleeding and cardiovascular events.
* Avoid concurrent use with other NSAIDs.
* Discontinue immediately if signs of GI bleeding, renal toxicity, or hypersensitivity occur.
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**Disclaimer:** This information is intended for healthcare professionals and does not substitute for complete prescribing information. Always consult the official drug labeling and current clinical guidelines before making therapeutic decisions.
