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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
* Pain associated with mild to moderate intensity, particularly dysmenorrhea.
* Rheumatoid arthritis and osteoarthritis (less common due to alternative options).
## Adult Dosing
* **Analgesia:** 500 mg every 6 to 8 hours as needed. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 to 8 hours, starting at the onset of bleeding and associated pain. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
## Pediatric Dosing
* Established pediatric dosing is not widely available or recommended for routine use. Use in children should be carefully considered and guided by specialist advice.
## Dose Adjustments
* **Renal Impairment:** Caution is advised. Dose reduction may be necessary in severe renal impairment.
* **Hepatic Impairment:** Caution is advised. Dose reduction may be necessary in severe hepatic impairment.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal toxicity. Consider lower doses and shorter durations.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria after taking aspirin or other NSAIDs.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Severe heart failure, renal impairment, or hepatic impairment.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulceration or gastrointestinal bleeding.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, headache, dizziness, rash, pruritus.
* **Serious:** Gastrointestinal bleeding, perforation, ulceration; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis); bronchospasm; anaphylaxis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Other NSAIDs:** Increased risk of adverse effects, including gastrointestinal bleeding.
* **Diuretics and Antihypertensives:** May reduce their efficacy and increase risk of renal toxicity.
* **Lithium, Methotrexate:** Increased serum levels and toxicity.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Monitor renal function (serum creatinine, BUN) and liver function (LFTs), especially in patients with pre-existing impairment or on long-term therapy.
* Monitor for signs of cardiovascular events.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Mefenamic acid is generally used for short-term symptomatic relief of pain.
* It is crucial to use the lowest effective dose for the shortest duration necessary to minimize risks.
* Advise patients to take with food or milk to reduce gastrointestinal upset.
* Discontinue immediately if signs of gastrointestinal bleeding or other serious adverse effects occur.
* Due to potential for significant gastrointestinal side effects, other NSAIDs with better safety profiles may be preferred for chronic inflammatory conditions.
**Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider and refer to the most current prescribing information for definitive guidance.
