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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties through the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including headache, dental pain, postoperative pain, and musculoskeletal pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 to 8 hours as needed. Not to exceed 1000 mg per dose or 4000 mg per day.
* **Dysmenorrhea:** 500 mg every 6 to 8 hours starting with the onset of pain and bleeding, usually for up to 3 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited safety and efficacy data. Dosing, if considered, would be highly individualized and require careful monitoring.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment. Data is limited.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment. Data is limited.
## 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 bleeding or history of recurrent gastrointestinal ulceration or bleeding.
* Severe renal or hepatic impairment.
* Severe heart failure.
## Adverse Effects
Common adverse effects include gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), dizziness, drowsiness, and headache. More serious effects include:
* **Gastrointestinal:** Ulceration, bleeding, perforation.
* **Cardiovascular:** Increased risk of thrombotic events (myocardial infarction, stroke), hypertension, edema.
* **Renal:** Renal papillary necrosis, interstitial nephritis, renal failure.
* **Hepatic:** Hepatotoxicity.
* **Hematologic:** Anemia, leukopenia.
* **Dermatologic:** Rash, pruritus, Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Hypersensitivity:** Anaphylactoid reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Aspirin:** May decrease the cardioprotective effect of low-dose aspirin and increase risk of GI toxicity.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics and Antihypertensives:** May reduce efficacy and increase risk of renal toxicity.
* **Lithium:** Increased serum lithium levels, potential toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding (melena, hematemesis).
* Monitor renal and hepatic function, especially with prolonged use or in patients with pre-existing impairment.
* Monitor blood pressure.
* Assess pain relief and inflammatory signs.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its short half-life, it is typically dosed every 6-8 hours.
* Long-term use is generally discouraged due to the potential for serious adverse effects, especially gastrointestinal and cardiovascular.
* The use of mefenamic acid in children is limited, and alternative analgesics are often preferred.
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**Disclaimer:** This information is intended for clinical use and does not replace professional medical advice. Always consult the most current prescribing information and professional resources for complete details and to verify this information before making any treatment decisions.
