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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It functions 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. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain and bleeding, and continuing for the duration of the dysmenorrhea symptoms.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be based on clinical judgment and specific product labeling, as efficacy and safety have not been fully determined for all age groups. Some sources suggest:
* **Pain/Inflammation:** 6.5 mg/kg/dose every 6 hours, not to exceed 500 mg/dose. Maximum daily dose 4 doses per day. Duration of use should not exceed 7 days.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be considered in severe impairment, though specific guidelines are lacking.
* **Hepatic Impairment:** Use with caution. Dose reduction may be considered in severe impairment, though specific guidelines are lacking.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* 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.
## Adverse Effects
* **Common:** Gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), dizziness, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal impairment; hepatic impairment; hypersensitivity reactions; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Diuretics and Antihypertensives:** May decrease their efficacy and increase risk of renal impairment.
## Monitoring
* **Gastrointestinal symptoms:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis).
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease.
* **Liver function:** Monitor LFTs, especially with prolonged use or in patients with hepatic impairment.
* **Blood pressure:** NSAIDs can cause new-onset hypertension or worsen existing hypertension.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize gastrointestinal upset.
* Consider lowest effective dose for the shortest duration necessary to minimize risks.
* Avoid concomitant use with other NSAIDs or aspirin.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and local institutional protocols for definitive guidance. Patient-specific factors should always be considered.*
