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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties. Its mechanism of action involves the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Relief of mild to moderate pain, including:
* Primary dysmenorrhea
* Headache
* Dental pain
* Musculoskeletal pain
## Adult Dosing
* **Dosage:** 500 mg orally every 6 hours as needed.
* **Maximum Daily Dose:** 1500 mg per day.
* **Duration:** Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children under 14 years of age due to limited safety and efficacy data. If used, dosing should be carefully considered and supervised by a healthcare professional.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Mefenamic acid is renally eliminated and can exacerbate renal dysfunction. Dose reduction may be necessary in severe impairment, though specific guidelines are lacking.
* **Hepatic Impairment:** Use with caution. Patients with hepatic impairment may have increased exposure to mefenamic acid.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of bronchospasm, urticaria, or allergic-type reactions after taking 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.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, headache, dizziness.
* **Serious:**
* **GI:** Ulceration, bleeding, perforation; exacerbation of inflammatory bowel disease.
* **Cardiovascular:** Increased risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke. Hypertension.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Elevated liver enzymes, hepatic impairment, jaundice.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Dermatologic:** Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis.
* **Hypersensitivity:** Anaphylaxis, angioedema, asthma exacerbation.
## 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 bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Diuretics:** Reduced efficacy and increased risk of nephrotoxicity.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and risk of toxicity.
* **ACE inhibitors and Angiotensin II Receptor Blockers (ARBs):** Increased risk of renal impairment.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those at risk.
* **Liver function:** Baseline and periodically, especially in patients with hepatic impairment.
* **GI symptoms:** Monitor for signs of bleeding or ulceration.
* **Blood pressure:** Monitor for new-onset hypertension or exacerbation of existing hypertension.
* **Cardiovascular risk factors:** Assess and manage appropriately.
## Clinical Pearls
* Mefenamic acid has a relatively short half-life and is typically taken multiple times a day.
* It should be taken with food or milk to minimize GI upset.
* Due to its potential for serious adverse effects, particularly GI and cardiovascular events, the lowest effective dose should be used for the shortest duration necessary.
* Consider risks versus benefits, especially in elderly patients or those with comorbidities.
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***Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant guidelines for complete and up-to-date information before making any clinical decisions.*
