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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties. Its mechanism of action involves the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed. Dosing should not exceed 7 days.
* **Maximum Daily Dose:** 1500 mg.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children under 14 years of age due to lack of established efficacy and safety data for many indications. Some sources suggest 6.5 mg/kg every 6 hours for pain, but this is not widely established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are established, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are established.
## Contraindications
* Known hypersensitivity to mefenamic acid 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.
* Inflammatory bowel disease.
* Active peptic ulceration or gastrointestinal bleeding.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* Central Nervous System: Dizziness, drowsiness.
* Renal: Sodium and fluid retention, edema.
* Hematologic: Leukopenia, eosinophilia.
* Other: Rash, pruritus.
Serious adverse effects include:
* Gastrointestinal bleeding, ulceration, and perforation.
* Cardiovascular thrombotic events.
* Renal toxicity, interstitial nephritis, papillary necrosis.
* Hepatotoxicity.
* Serious skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).
* Bronchospasm.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Aspirin:** May reduce the cardioprotective effects of low-dose aspirin; increased risk of GI toxicity.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics and Antihypertensives:** May reduce antihypertensive effect and increase risk of renal toxicity.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and risk of toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those receiving concomitant nephrotoxic agents.
* **Hepatic function:** Baseline and periodic monitoring is recommended.
* **Gastrointestinal bleeding:** Monitor for signs and symptoms (e.g., melena, hematemesis, abdominal pain).
* **Blood pressure:** NSAIDs can cause hypertension.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize gastrointestinal upset.
* Due to its short half-life, frequent dosing is required.
* Consider the risks of gastrointestinal bleeding and cardiovascular events associated with NSAID use, especially in elderly patients or those with a history of these conditions.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant guidelines before making any treatment decisions. Dosing and recommendations may vary based on individual patient factors and local institutional protocols.
