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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exerts analgesic and anti-inflammatory effects by inhibiting 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 orally every 6 hours as needed.
* **Dysmenorrhea:** 500 mg orally every 6 hours as needed, usually initiated at the onset of pain and continued for no more than 6 days per menstrual cycle.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited data and potential for adverse effects.
## Dose Adjustments
No specific dose adjustments are typically required for hepatic or renal impairment, but caution is advised, and the lowest effective dose should be used.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, allergic rhinitis, or urticaria precipitated by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Significant renal or hepatic impairment.
* Known or suspected gastrointestinal bleeding.
## Adverse Effects
Common: Diarrhea, nausea, vomiting, abdominal pain, constipation, dizziness, headache, rash.
Serious: Gastrointestinal bleeding, ulceration, perforation; renal failure; hepatic toxicity; cardiovascular thrombotic events; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Other NSAIDs / Aspirin:** Increased risk of gastrointestinal toxicity and additive effects.
* **Diuretics / ACE inhibitors / Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels, leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Renal function (BUN, creatinine) periodically, especially in patients with pre-existing renal disease or those receiving concomitant nephrotoxic agents.
* Liver function tests (AST, ALT) periodically, especially in patients with impaired hepatic function.
* Blood pressure.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Maximum duration of use is typically 7 days for pain and 6 days for dysmenorrhea.
* Should be used at the lowest effective dose for the shortest duration necessary to control symptoms.
* Consider the risk of cardiovascular thrombotic events, myocardial infarction, and stroke associated with NSAID use.
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**Disclaimer:** This information is intended for clinical use and does not replace the need for independent verification of current prescribing information from approved sources. Always consult the official drug monograph or product labeling for complete and up-to-date details.
