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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class, primarily used for short-term relief of mild to moderate pain. It acts by inhibiting cyclooxygenase (COX) enzymes, which reduces prostaglandin synthesis.
## Primary Indications
* Pain, mild to moderate, including:
* Menstrual pain (primary dysmenorrhea)
* Dental pain
* Musculoskeletal pain
## Adult Dosing
The typical starting dose is 500 mg every 4 to 6 hours as needed.
Maximum daily dose: 1500 mg.
Treatment duration should generally be limited to 7 days.
## Pediatric Dosing
Due to insufficient data on safety and efficacy, mefenamic acid is generally not recommended for use in children under 14 years of age.
## Dose Adjustments
No specific dose adjustments are routinely recommended for renal or hepatic impairment. However, caution is advised, and close monitoring for adverse effects is necessary, as NSAIDs can exacerbate pre-existing renal or hepatic conditions.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria induced by aspirin or other NSAIDs.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or a history of recurrent GI ulceration or hemorrhage.
* Severe renal or hepatic impairment.
* Severe heart failure.
## Adverse Effects
**Common:**
* GI upset (nausea, vomiting, diarrhea, constipation, abdominal pain)
* Dyspepsia
* Dizziness
* Headache
**Serious:**
* GI ulceration and bleeding
* Cardiovascular thrombotic events (MI, stroke)
* Renal toxicity (acute kidney injury, interstitial nephritis)
* Hepatic injury
* Hypersensitivity reactions (including Stevens-Johnson syndrome, toxic epidermal necrolysis)
* Exacerbation of asthma
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI toxicity and renal adverse effects.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
* **ACE inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of renal dysfunction.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* **GI Symptoms:** Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* **Renal Function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic Function:** Monitor LFTs if liver dysfunction is suspected.
* **Blood Pressure:** Monitor blood pressure, especially when used with antihypertensives.
* **Signs of Cardiovascular Events:** Patients should be advised to seek medical attention if chest pain, shortness of breath, weakness, or slurring of speech occur.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize GI upset.
* Use the lowest effective dose for the shortest duration necessary.
* Be aware of the increased risk of serious cardiovascular events and GI bleeding associated with NSAID use.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and local protocols for definitive guidance.*
