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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 is a reversible inhibitor of cyclooxygenase (COX) enzymes, reducing the synthesis of prostaglandins.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea).
* Pain associated with dental procedures.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain or bleeding.
**Maximum dose:** 1500 mg per 24 hours. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited data and potential safety concerns.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are established, but NSAIDs can precipitate renal failure, especially in patients with pre-existing renal disease.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are established, but NSAIDs can exacerbate liver dysfunction.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or history of recurrent GI ulceration or bleeding.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, constipation, flatulence, dyspepsia, and rash. Serious adverse effects include:
* **GI:** Ulceration, bleeding, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, hypertension.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI toxicity and additive effects.
* **ACE inhibitors, ARBs, diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **GI symptoms:** Assess for signs and symptoms of GI bleeding or ulceration.
* **Renal function:** Monitor BUN and serum creatinine, especially in patients with risk factors for renal impairment.
* **Liver function:** Monitor LFTs if used long-term or in patients with hepatic impairment.
* **Blood pressure:** Monitor for hypertension.
* **Signs of hypersensitivity reactions.**
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Advise patients to take with food or milk to minimize GI upset.
* Discontinue immediately if signs of GI bleeding, renal toxicity, hepatic toxicity, or hypersensitivity occur.
* Consider the lowest effective dose for the shortest duration necessary.
* Use with caution in elderly patients and those with cardiovascular disease, renal impairment, hepatic impairment, or a history of GI issues.
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*This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for complete and up-to-date details.*
