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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 and for the treatment of primary dysmenorrhea.
## Primary Indications
* Mild to moderate pain (e.g., dental pain, post-operative pain).
* Primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 4000 mg per day.
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed, starting with the onset of pain or bleeding. Do not exceed 4000 mg per day.
## Pediatric Dosing
* **Pain and Dysmenorrhea:** Mefenamic acid is not generally recommended for children under 14 years of age. Limited data exists for use in pediatric populations, and caution is advised.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment.
* **Elderly:** Increased risk of adverse effects. Consider lower doses and closer monitoring.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or history of recurrent gastrointestinal bleeding.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, rash, dizziness, somnolence.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions (including anaphylaxis); exacerbation of asthma; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **SSRIs and SNRIs:** Increased risk of gastrointestinal bleeding.
* **Diuretics and ACE inhibitors:** May reduce antihypertensive effect and increase risk of nephrotoxicity.
* **Lithium:** Mefenamic acid can increase serum lithium levels. Monitor lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Other NSAIDs and Aspirin:** Increased risk of gastrointestinal adverse effects and other side effects.
## Monitoring
* **Renal function:** Creatinine, BUN, especially in patients with pre-existing renal disease, dehydration, or receiving concomitant nephrotoxic agents.
* **Hepatic function:** Liver enzymes, especially in patients with hepatic impairment.
* **Gastrointestinal symptoms:** Monitor for signs of bleeding (e.g., melena, hematemesis).
* **Cardiovascular risk factors:** Advise patients to seek immediate medical attention for chest pain, shortness of breath, weakness, slurring of speech, or sudden numbness/weakness.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Limit treatment duration to the shortest effective period due to potential for gastrointestinal and cardiovascular adverse events.
* Mefenamic acid is not a substitute for aspirin in cardiovascular prophylaxis.
* Discontinue if signs of hepatic or renal dysfunction, or serious adverse reactions occur.
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*This information is intended for healthcare professionals and should not replace consultation with a qualified medical provider. Always consult the most current prescribing information and institutional protocols for definitive guidance.*
