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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic and anti-inflammatory properties. Its mechanism of action involves the inhibition of cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, particularly dysmenorrhea.
* Relief of inflammatory manifestations of rheumatoid arthritis.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Treatment should not exceed 7 days.
* **Rheumatoid Arthritis:** 500 mg every 6 hours. Not typically recommended for long-term use in rheumatoid arthritis due to potential for increased adverse events.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age for pain management due to lack of established safety and efficacy data. Dosing for children 14 years and older is the same as adult dosing for pain.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised. Use the lowest effective dose for the shortest duration necessary.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* Patients with a 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 (GI) bleeding or ulcer disease.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, dyspepsia, headache, dizziness, rash, pruritus.
* **Serious:** GI bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal toxicity (acute kidney injury, interstitial nephritis); hepatic toxicity; hypersensitivity reactions; 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.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI adverse effects and potential for reduced cardioprotective effect of low-dose aspirin.
* **Diuretics and antihypertensives:** NSAIDs can reduce their efficacy and increase the risk of renal toxicity.
* **Lithium:** NSAIDs can increase serum lithium levels.
* **Methotrexate:** NSAIDs can increase methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Assess for cardiovascular risk factors and monitor for signs of cardiovascular events.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Mefenamic acid is generally intended for short-term use only.
* Administer with food or milk to minimize GI upset.
* Diarrhea is a particularly common and sometimes dose-limiting side effect.
* Avoid concomitant use with other NSAIDs.
* Use with caution in patients with a history of asthma, cardiovascular disease, or hypertension.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and guidelines, or a qualified healthcare provider, for diagnosis and treatment recommendations.*
