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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Short-term management of mild to moderate pain, particularly:
* Primary dysmenorrhea
* Headache
* Dental pain
* Musculoskeletal pain
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain or bleeding.
* **Maximum Daily Dose:** 1500 mg per day.
* **Duration of Therapy:** Not recommended for use for more than 7 consecutive days.
## Pediatric Dosing
* **Pain and Fever:**
* **1-3 years (10-15 kg):** 75 mg every 8 hours.
* **4-6 years (16-21 kg):** 125 mg every 8 hours.
* **7-12 years (22-40 kg):** 250 mg every 8 hours.
* **Note:** Dosing in children should be guided by prescriber judgment and local protocols. The duration of treatment should be as short as possible.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be considered in severe impairment, but specific guidelines are not well-established. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Dose reduction may be considered in severe impairment, but specific guidelines are not well-established. Monitor liver function closely.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal dysfunction. Consider a lower starting dose and monitor closely.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or history of gastrointestinal bleeding or perforation related to previous NSAID use.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, headache, dizziness, rash.
* **Serious:**
* **Gastrointestinal:** Bleeding, ulceration, perforation.
* **Cardiovascular:** Myocardial infarction, stroke, hypertension, heart failure.
* **Renal:** Acute kidney injury, interstitial nephritis.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Aspirin (low-dose):** May decrease the cardioprotective effect of aspirin.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Diuretics:** Reduced diuretic and antihypertensive effect; increased risk of nephrotoxicity.
* **Lithium:** Increased serum lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
## Monitoring
* **GI Bleeding:** Monitor for signs and symptoms such as melena, hematemesis, abdominal pain.
* **Renal Function:** Baseline and periodic assessment of renal function (BUN, creatinine).
* **Liver Function:** Baseline and periodic assessment of liver function (ALT, AST).
* **Blood Pressure:** Regular monitoring, especially in patients with hypertension.
* **Signs of Cardiovascular Events:** Educate patients on warning signs of MI and stroke.
## Clinical Pearls
* Mefenamic acid is generally intended for short-term use only.
* Take with food or milk to minimize gastrointestinal upset.
* Avoid concurrent use with other NSAIDs.
* Educate patients on the risks of serious GI and cardiovascular events.
* Due to its potential for rapid onset, it may be useful for acute pain.
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*This information is intended for clinical use and does not substitute for professional medical advice. Always consult the most current prescribing information and guidelines before administering any medication.*
