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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain. It also possesses anti-inflammatory and antipyretic properties.
## Primary Indications
* Pain associated with osteoarthritis and rheumatoid arthritis
* Menstrual pain (dysmenorrhea)
* Mild to moderate pain of other origins
## Adult Dosing
* **Initial dose:** 500 mg orally every 8 hours.
* **Subsequent doses:** 250 mg orally every 4 to 6 hours as needed.
* **Maximum dose:** Do not exceed 1000 mg in any 24-hour period or 4000 mg per day if using for longer durations (though it is intended for short-term use). Duration of treatment should not exceed 7 days.
## Pediatric Dosing
* **Children 6 months and older:** 6.5 mg/kg orally every 6 to 8 hours.
* **Maximum dose:** Not to exceed adult maximums.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are established, but NSAIDs can worsen renal function.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are established.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs
* History of bronchospasm, asthma, rhinitis, or urticaria precipitated by aspirin or other NSAIDs
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery
* Active gastrointestinal bleeding or ulceration
* Severe renal or hepatic impairment
* Pregnancy (third trimester)
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal failure; hepatic failure; myocardial infarction; stroke; hypersensitivity reactions; Stevens-Johnson syndrome; toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Diuretics, ACE inhibitors, ARBs:** Decreased antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels. Monitor lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
* **Other NSAIDs (including aspirin):** Increased risk of gastrointestinal toxicity and potential for reduced cardioprotective effects of low-dose aspirin.
## Monitoring
* **Gastrointestinal symptoms:** Monitor for signs of 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, especially in patients with pre-existing hepatic disease or those at risk.
* **Blood pressure:** Monitor for potential increases.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only due to the increased risk of serious gastrointestinal, cardiovascular, and renal adverse events with prolonged use.
* Administer with food or milk to minimize gastrointestinal upset.
* Onset of action for pain relief is typically within 1 hour.
* Due to its potent analgesic effects, it can mask symptoms of certain infections.
**Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Always verify current prescribing information, contraindications, warnings, and drug interactions with the most up-to-date official product labeling or a trusted pharmaceutical reference before prescribing or dispensing.
