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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term management of mild to moderate pain. It is also used for the treatment of primary dysmenorrhea.
## Primary Indications
* Mild to moderate pain
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed. Do not exceed 4000 mg per day.
* **Primary Dysmenorrhea:** 500 mg orally every 6 hours, starting at the onset of pain and bleeding, and continuing for the duration of symptoms (typically 2-3 days). Do not exceed 4000 mg per day.
* **Duration:** Mefenamic acid is intended for short-term use only. Treatment should generally not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age for pain management. For dysmenorrhea, it is typically used in adolescents.
* **Primary Dysmenorrhea (Adolescents ≥ 14 years):** 500 mg orally every 6 hours, starting at the onset of pain and bleeding, and continuing for the duration of symptoms. Do not exceed 4000 mg per day.
## Dose Adjustments
No dose adjustment is typically required for renal or hepatic impairment, but caution is advised due to potential for NSAID-induced organ damage. Use with caution and consider lower doses in elderly patients.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or history of recurrent GI ulceration or hemorrhage.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* Pregnancy (especially third trimester).
## Adverse Effects
Common: Diarrhea, nausea, vomiting, abdominal pain, dyspepsia, headache, dizziness, rash.
Serious:
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **GI:** Ulceration, bleeding, perforation.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Elevated liver enzymes, hepatitis.
* **Hematologic:** Anemia, prolonged bleeding time.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of GI toxicity and bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **ACE inhibitors and Angiotensin II Receptor Blockers (ARBs):** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic effect and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis, abdominal pain).
* Monitor for signs of cardiovascular events (e.g., chest pain, shortness of breath, sudden weakness).
* Monitor renal function (BUN, creatinine) especially in patients with pre-existing renal disease or at risk.
* Monitor liver function tests (AST, ALT) especially with prolonged use.
* Monitor blood pressure.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to its short half-life, it requires frequent dosing.
* It is generally not preferred for chronic pain management due to potential for GI and renal toxicity.
* It is important to counsel patients on the risks of NSAID use, including GI bleeding, cardiovascular events, and renal impairment.
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*Disclaimer: This information is for educational purposes only and does not substitute for professional medical advice. Always consult with a qualified healthcare provider and refer to the most current prescribing information and guidelines before making any treatment decisions.*
