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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. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Pain, including menstrual pain (dysmenorrhea), headache, dental pain, and musculoskeletal pain.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Maximum dose:** 1500 mg per day. Dosing should not exceed 7 days for self-medication.
## Pediatric Dosing
* Mefenamic acid is **not recommended** for children under 14 years of age due to insufficient data regarding safety and efficacy.
## 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.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal events. Use the lowest effective dose for the shortest duration.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, 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 renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal toxicity (acute kidney injury, interstitial nephritis); hepatic toxicity; hypersensitivity reactions; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI adverse effects and may reduce cardioprotective effects of low-dose aspirin.
* **ACE inhibitors, ARBs, diuretics:** May decrease antihypertensive effect and increase risk of renal toxicity.
* **Lithium:** Increased serum lithium levels. Monitor lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* **Renal function:** Baseline and periodic monitoring of serum creatinine and BUN, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic medications.
* **Hepatic function:** Baseline and periodic monitoring of LFTs, especially in patients with hepatic impairment or those on long-term therapy.
* **Blood pressure:** Monitor blood pressure, especially in patients with hypertension.
* **Signs of hypersensitivity:** Monitor for rash, urticaria, and angioedema.
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Use the lowest effective dose for the shortest possible duration to minimize risks.
* Avoid concurrent use with other NSAIDs.
* Be aware of the increased risk of cardiovascular and gastrointestinal events associated with NSAID use.
* Discontinue immediately if signs of serious adverse effects occur.
**Disclaimer:** This information is intended for healthcare professionals. Always consult the current official prescribing information and relevant literature for complete details before making any clinical decisions. Dosing and recommendations may vary based on individual patient factors and local protocols.
