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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Mild to moderate pain, particularly menstrual pain (dysmenorrhea).
* Rheumatoid arthritis and osteoarthritis (less commonly used for chronic inflammatory conditions due to potential GI toxicity).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment duration should not exceed 7 days for pain.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain or bleeding.
* **Rheumatoid Arthritis/Osteoarthritis:** 750 mg every 6 hours initially, may be reduced to 500 mg every 6 hours. Maximum daily dose is 1500 mg.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for use in children under 14 years of age for pain management due to limited safety and efficacy data. Specific pediatric dosing is not established for this indication.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised. NSAIDs can exacerbate pre-existing renal disease.
## 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.
* Inflammatory bowel disease.
* Severe heart failure, renal impairment, or hepatic impairment.
* Pregnancy in the third trimester.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, dizziness, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal toxicity; hepatic toxicity; hypersensitivity reactions (including anaphylaxis); Stevens-Johnson syndrome, toxic epidermal necrolysis; bronchospasm; fluid retention and edema; hypertension.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **SSRIs and SNRIs:** Increased risk of GI bleeding.
* **ACE inhibitors, ARBs, Beta-blockers:** Reduced antihypertensive effect; increased risk of renal impairment.
* **Diuretics:** Reduced diuretic effect; increased risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Especially in patients with pre-existing hepatic disease.
* **Signs and symptoms of GI bleeding:** Occult blood in stool, melena, hematemesis.
* **Blood pressure:** NSAIDs can cause hypertension.
## Clinical Pearls
* Mefenamic acid is typically used for short-term pain relief due to its potential for GI side effects.
* It is most effective when taken with food or milk to reduce gastric irritation.
* Use the lowest effective dose for the shortest duration necessary to minimize risks.
* Avoid concomitant use with other NSAIDs.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for clinical judgment. Always consult the most current prescribing information and local protocols for definitive guidance.*
