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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for short-term relief of mild to moderate pain. It has analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Pain associated with dysmenorrhea.
* Mild to moderate pain from other causes (e.g., headaches, muscle aches, dental pain).
## Adult Dosing
* **Initial dose:** 500 mg by mouth every 4 to 6 hours as needed.
* **Maximum daily dose:** 1500 mg.
* **Duration:** Treatment should not exceed 7 days.
## Pediatric Dosing
* No established pediatric dosing. Use in children under 14 years of age is generally not recommended due to lack of safety and efficacy data.
## Dose Adjustments
* **Renal impairment:** Use with caution. Dose reduction may be necessary, though specific guidelines are not well-established. Monitor renal function closely.
* **Hepatic impairment:** Use with caution. Dose reduction may be necessary. Monitor hepatic function closely.
* **Elderly:** Increased risk of adverse effects. Consider lower doses and shorter duration.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* Active gastrointestinal (GI) ulceration or bleeding.
* Inflammatory bowel disease (active).
* Severe heart failure, renal impairment, or hepatic impairment.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, heartburn, rash.
* **Serious:**
* **GI:** GI bleeding, ulceration, perforation.
* **Cardiovascular:** Increased risk of thrombotic events (myocardial infarction, stroke), hypertension.
* **Renal:** Renal papillary necrosis, interstitial nephritis, acute renal failure, nephrotic syndrome.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Lithium:** Mefenamic acid can decrease lithium clearance, leading to increased lithium levels and toxicity.
* **Methotrexate:** Mefenamic acid can decrease methotrexate clearance, leading to increased methotrexate levels and toxicity.
* **Diuretics and Antihypertensives:** May diminish their effects.
* **ACE inhibitors and Angiotensin II Receptor Blockers (ARBs):** May increase risk of renal impairment.
## Monitoring
* **GI status:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis).
* **Renal function:** Monitor BUN, creatinine, and urine output, especially in patients at risk.
* **Hepatic function:** Monitor LFTs (ALT, AST), especially with prolonged use or in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for hypertension.
* **Signs of hypersensitivity reactions.**
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize GI upset.
* Use the lowest effective dose for the shortest duration necessary.
* Avoid concurrent use with other NSAIDs, including aspirin, unless specifically indicated and managed.
* Advise patients to report any signs of GI bleeding, cardiovascular events, or severe allergic reactions immediately.
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**Disclaimer:** This information is intended for clinical use and does not replace the official prescribing information or professional medical advice. Always consult the most current drug monograph and institutional protocols for complete details and to verify dosing and safety information before prescribing or administering any medication.
