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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term symptomatic treatment of mild to moderate pain. It is also used for the management of primary dysmenorrhea.
## Primary Indications
* Pain (mild to moderate)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed.
* **Primary Dysmenorrhea:** 500 mg orally every 6 hours as needed, starting at the onset of pain and bleeding, usually for up to 3 days.
**Maximum Daily Dose:** 1500 mg in a 24-hour period. The duration of treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children under 14 years of age. Limited data exists for its use in younger pediatric populations, and it should only be considered if other treatments are ineffective and under specialist guidance.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised due to potential for NSAID-related toxicity. Use in patients with severe renal or hepatic impairment is generally not recommended.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, allergic rhinitis, or urticaria precipitated by aspirin or other NSAIDs.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* Central Nervous System: Dizziness, drowsiness.
* Renal: Fluid retention, edema.
* Hematologic: Anemia.
Serious adverse effects may include gastrointestinal bleeding, perforation, ulceration, renal failure, cardiovascular events, and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of gastrointestinal toxicity and potential for additive pharmacodynamic effects.
* **ACE Inhibitors and ARBs:** May decrease antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May decrease diuretic efficacy and increase risk of renal impairment.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Renal function, especially in patients with pre-existing renal disease or those at risk for renal toxicity.
* Blood pressure.
* Signs of hypersensitivity or allergic reactions.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Short-term use is recommended due to increased risk of serious adverse events with prolonged use.
* Mefenamic acid is not typically a first-line agent for chronic pain.
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**Disclaimer:** Always consult the most current prescribing information and institutional protocols for definitive dosing, indications, and safety guidance.
