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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It has analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Mild to moderate pain, particularly menstrual pain (dysmenorrhea).
* Pain and inflammation associated with conditions like rheumatoid arthritis and osteoarthritis (though less commonly used than other NSAIDs for chronic conditions).
## Adult Dosing
* **Pain:** 500 mg orally every 8 hours as needed.
* **Dysmenorrhea:** 500 mg orally every 8 hours, starting at the onset of pain or bleeding, whichever comes first, for up to 3 days.
* **Maximum Daily Dose:** 1500 mg.
## Pediatric Dosing
Mefenamic acid is **not recommended for children under 14 years of age** due to potential toxicity and lack of established dosing.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment. Avoid in severe renal disease.
* **Hepatic Impairment:** Use with caution. Data is limited. Avoid in severe hepatic disease.
* **Elderly:** Increased risk of adverse events. Use the lowest effective dose.
## 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 history of recurrent gastrointestinal bleeding.
* Severe renal or hepatic impairment.
* Pregnancy (third trimester).
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal papillary necrosis and other renal injury; hepatic injury; cardiovascular thrombotic events; 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.
* **ACE inhibitors and ARBs:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic effect and increase risk of renal impairment.
* **Lithium:** Increased lithium levels and potential for toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Renal function (BUN, creatinine), especially in patients with risk factors.
* Liver function tests, especially with prolonged use or pre-existing hepatic disease.
* Blood pressure, as NSAIDs can cause hypertension.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its short half-life and risk of gastrointestinal side effects, it is generally recommended for short-term use only.
* Diarrhea is a relatively common and sometimes dose-limiting side effect.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines before making clinical decisions. Dosing and safety profiles can vary, and individual patient factors must be considered.
