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# Mefenamic Acid (Meftal-P)
## 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
* Mild to moderate pain, including menstrual pain (dysmenorrhea).
* Inflammation associated with conditions like rheumatoid arthritis and osteoarthritis (though less commonly used for chronic conditions due to safety profile).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed, starting at the onset of menstrual pain and continuing for up to 3 days.
* **Maximum daily dose:** 1500 mg. Duration of use typically limited to 7 days.
## Pediatric Dosing
* **Age:** Generally not recommended for children under 14 years of age for pain and fever, though some sources suggest it for specific indications and under strict medical supervision. Limited pediatric data available. If used, dosing is weight-based and should be determined by a pediatrician.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, 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 renal or hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, headache, dizziness.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal impairment/failure; hepatic impairment; cardiovascular thrombotic events (myocardial infarction, stroke); hypersensitivity reactions; 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.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI toxicity, renal toxicity, and additive pharmacodynamic effects.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium, Methotrexate:** Increased serum concentrations and toxicity.
## Monitoring
* **GI Symptoms:** Monitor for signs of bleeding (melena, hematemesis) or ulceration.
* **Renal Function:** Assess baseline and periodic renal function, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* **Hepatic Function:** Assess baseline and periodic liver function tests, particularly in patients with hepatic impairment.
* **Blood Pressure:** Monitor blood pressure, especially in patients with hypertension.
* **Signs of Cardiovascular Events:** Educate patients on symptoms of MI and stroke.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use (up to 7 days) due to increased risk of GI toxicity with prolonged use.
* Administer with food or milk to minimize GI upset.
* Consider risks versus benefits, especially in elderly patients or those with cardiovascular, renal, or hepatic disease.
* Due to potential CNS effects, caution patients regarding driving or operating machinery.
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**Disclaimer:** This information is intended for clinical professionals. It is essential to consult the most current prescribing information and relevant literature for definitive guidance. Dosing and recommendations may vary based on patient-specific factors and local protocols.
