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# Mefenamic acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term symptomatic treatment of mild to moderate pain. It functions by inhibiting cyclooxygenase (COX) enzymes, thus reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea), headache, dental pain, and postpartum pain.
## Adult Dosing
* **Pain:** 500 mg every 6 hours, as needed.
* **Maximum Daily Dose:** 1500 mg per day. Treatment should not exceed 7 days.
## Pediatric Dosing
* **Age:** Mefenamic acid is generally not recommended for children under 14 years of age due to limited efficacy and safety data. If used, doses are typically based on weight.
* **Weight-based (example, consult specific guidelines):** 6.5 mg/kg every 6 hours.
* **Maximum Daily Dose:** Similar to adults, but should not exceed 1500 mg per day.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment, though specific guidelines vary. Avoid in end-stage renal disease.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal events. Consider lower doses and closer monitoring.
## Contraindications
* 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.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Active gastrointestinal bleeding or history of recurrent gastrointestinal bleeding.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, dizziness, headache, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions (including anaphylaxis); Stevens-Johnson syndrome/toxic epidermal necrolysis; exacerbation of asthma; hemolytic anemia.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **SSRIs/SNRIs:** Increased risk of gastrointestinal bleeding.
* **ACE inhibitors/ARBs:** Reduced antihypertensive effect; increased risk of renal impairment.
* **Diuretics:** Reduced diuretic effect; increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Other NSAIDs:** Increased risk of adverse effects.
## Monitoring
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease, elderly patients, or those on concomitant nephrotoxic agents.
* **Hepatic function:** Monitor LFTs if liver dysfunction is suspected.
* **Gastrointestinal symptoms:** Assess for signs and symptoms of bleeding (e.g., melena, hematemesis).
* **Cardiovascular risk:** Assess for signs of thrombotic events.
* **Blood pressure:** Monitor for changes, especially in hypertensive patients.
## Clinical Pearls
* Mefenamic acid is typically recommended for short-term use only due to the increased risk of gastrointestinal and cardiovascular adverse events with prolonged use.
* Administer with food or milk to minimize gastrointestinal upset.
* Consider the GI risks, especially in elderly patients or those with a history of ulcers or bleeding.
* It is particularly effective for dysmenorrhea due to its effect on prostaglandin inhibition.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information, institutional guidelines, and patient-specific factors before making any treatment decisions.*
