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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term treatment of mild to moderate pain. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Pain associated with osteoarthritis and rheumatoid arthritis (less common due to GI risks compared to other NSAIDs).
* Primary dysmenorrhea.
* Mild to moderate pain (e.g., dental pain, musculoskeletal pain).
## Adult Dosing
* **Initial dose:** 500 mg.
* **Subsequent doses:** 250 mg every 6 hours as needed.
* **Maximum daily dose:** 1500 mg.
* **Duration of therapy:** Typically recommended for short-term use (e.g., no more than 7 days).
## Pediatric Dosing
* Mefenamic acid is **not typically recommended** for use in children under 14 years of age due to lack of established safety and efficacy data, and increased risk of adverse effects.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary; consult prescribing information for specific guidance.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary; consult prescribing information for specific guidance.
* **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, other NSAIDs, or any component of the formulation.
* 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.
* Active gastrointestinal bleeding or history of recurrent gastrointestinal perforation or ulceration.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Pregnancy, particularly in the third trimester.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, dizziness, headache, rash.
* **Serious:**
* **Gastrointestinal:** Ulceration, bleeding, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Renal:** Renal toxicity, interstitial nephritis, papillary necrosis.
* **Hepatic:** Elevated liver enzymes, hepatitis.
* **Hematologic:** Anemia, thrombocytopenia, leukopenia.
* **Hypersensitivity:** Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Other:** Bronchospasm, aseptic meningitis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Lithium:** Increased serum lithium levels, risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Diuretics and Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** NSAIDs can reduce their efficacy and increase the risk of renal toxicity.
* **Ciclosporin/Tacrolimus:** Increased risk of nephrotoxicity.
## Monitoring
* **GI Symptoms:** Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis, epigastric pain).
* **Renal Function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those taking concomitant nephrotoxic agents.
* **Hepatic Function:** Monitor liver function tests (ALT, AST) periodically.
* **Blood Pressure:** Monitor blood pressure, especially in patients with hypertension.
* **Fluid Retention/Edema:** Monitor for signs of fluid retention.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for gastrointestinal toxicity, it is often reserved for situations where other NSAIDs may be contraindicated or less effective, or for short-term use only.
* Diarrhea is a relatively common side effect and can be dose-limiting.
* Avoid concomitant use with other NSAIDs.
* Ensure patients are aware of the signs and symptoms of serious adverse effects.
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*This information is intended for clinical use and does not substitute for professional medical advice. Always consult the most current prescribing information and clinical guidelines before making treatment decisions.*
