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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a non-steroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis and exerting analgesic, anti-inflammatory, and antipyretic effects.
## Primary Indications
* Short-term relief of mild to moderate pain, including menstrual pain (dysmenorrhea), headache, dental pain, and musculoskeletal pain.
* Relief of pain and inflammation associated with osteoarthritis and rheumatoid arthritis (less commonly used for chronic conditions due to GI risk).
## Adult Dosing
* **Analgesia:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum daily dose:** 1500 mg. Treatment duration should not exceed 7 days.
## Pediatric Dosing
* **Established pediatric dosing is not widely available or recommended by many regulatory bodies due to safety concerns and lack of robust clinical trial data.** Some sources suggest dosing based on weight for specific indications, but this should be done with extreme caution and under specialist supervision.
* **Example (use with caution and confirm with local guidelines/pediatric specialist):** 6.5 mg/kg every 6 hours as needed for pain, not to exceed 500 mg per dose or 1500 mg per day. Duration should be limited.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be considered in severe renal impairment, but specific guidelines are lacking. Avoid in severe renal disease.
* **Hepatic Impairment:** Use with caution. May require dose reduction in moderate hepatic impairment. Avoid in severe hepatic disease.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal dysfunction. Use the lowest effective dose for the shortest duration.
## Contraindications
* 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 peptic ulceration or history of recurrent peptic ulceration.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), dyspepsia, headache, dizziness, rash, pruritus.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal failure, interstitial nephritis; hepatic dysfunction; cardiovascular thrombotic events (MI, stroke); hypersensitivity reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis; bronchospasm; fluid retention, edema; exacerbation of inflammatory bowel disease.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal.
* **ACE inhibitors/ARBs/Diuretics:** May reduce antihypertensive effect and increase risk of renal dysfunction.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
## Monitoring
* **Renal function:** Baseline and periodic monitoring, especially in patients with pre-existing renal disease, the elderly, or those on concomitant nephrotoxic agents.
* **Hepatic function:** Baseline and periodic monitoring, especially in patients with pre-existing liver disease.
* **Gastrointestinal symptoms:** Monitor for signs and symptoms of bleeding or ulceration.
* **Blood pressure:** NSAIDs can cause new-onset hypertension or worsen existing hypertension.
* **Signs of hypersensitivity:** Rash, difficulty breathing.
## Clinical Pearls
* Mefenamic acid is typically used for short-term pain relief due to its potential for gastrointestinal and renal side effects.
* It is generally not preferred for chronic inflammatory conditions due to a less favorable safety profile compared to other NSAIDs.
* Ensure adequate hydration to minimize renal risk.
* Advise patients to report any signs of gastrointestinal bleeding (e.g., black, tarry stools; coffee-ground emesis) or hypersensitivity reactions immediately.
* Due to limited pediatric data, use in children should be approached with extreme caution and under strict medical supervision.
***
**Disclaimer:** This information is intended for healthcare professionals and does not replace comprehensive drug information resources. Always consult the most current prescribing information and relevant guidelines before making clinical decisions.
