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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It acts 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 every 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum Daily Dose:** 1500 mg. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to insufficient data on safety and efficacy.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is established, but dose should be minimized, and renal function monitored.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment is established, but dose should be minimized, and liver function monitored.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria induced by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or history of recurrent GI ulceration/bleeding.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Last trimester of pregnancy.
## Adverse Effects
Common adverse effects include GI disturbances (nausea, vomiting, diarrhea, abdominal pain, dyspepsia), dizziness, and headache. More serious risks associated with NSAIDs include:
* **Cardiovascular:** Myocardial infarction, stroke, hypertension, heart failure.
* **Gastrointestinal:** Ulceration, bleeding, perforation.
* **Renal:** Acute kidney injury, interstitial nephritis.
* **Hepatic:** Hepatotoxicity.
* **Hematologic:** Anemia, prolonged bleeding time.
* **Dermatologic:** 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.
* **Other NSAIDs or Salicylates:** Increased risk of GI toxicity and potential for additive pharmacodynamic effects.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) or Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **ACE inhibitors, ARBs, Beta-blockers:** Reduced antihypertensive effect; increased risk of renal impairment.
* **Diuretics:** Reduced diuretic effect; increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor for signs of cardiovascular events (e.g., chest pain, shortness of breath).
* Monitor renal and hepatic function, especially with prolonged use or in patients with pre-existing impairment.
* Monitor blood pressure.
## Clinical Pearls
* Due to its short half-life, mefenamic acid typically requires dosing every 6 hours for effective pain relief.
* It should be taken with food or milk to minimize GI upset.
* Maximum duration of use is generally limited to 7 days due to increased risk of adverse effects with prolonged therapy.
* Patients should be advised to avoid concurrent use of other NSAIDs or aspirin unless specifically directed by a healthcare provider.
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*This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the current prescribing information and a qualified healthcare provider for any questions regarding drug therapy.*
