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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea), dental pain, and musculoskeletal pain.
* Symptomatic relief of rheumatoid arthritis and osteoarthritis (though not typically a first-line agent for chronic conditions).
## Adult Dosing
* **Pain:** 500 mg every 6 to 8 hours as needed. Do not exceed 4000 mg per day. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Rheumatoid Arthritis / Osteoarthritis:** Doses may vary, often starting at 500 mg three times daily, but typically limited to short-term use. Consult specific protocols.
## Pediatric Dosing
* **Pain:** Generally not recommended for children under 14 years of age due to lack of established efficacy and safety data. Some sources suggest 6.5 mg/kg/dose every 8 hours for children aged 6 months to 14 years, not exceeding adult doses. **Confirm local protocol and age restrictions.**
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduced doses may be necessary, and prolonged use should be avoided. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Reduced doses may be necessary. Monitor hepatic function closely.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal issues. Consider lower doses and shorter durations.
## Contraindications
* Known 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.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Gastrointestinal:** Dyspepsia, nausea, vomiting, diarrhea, constipation, abdominal pain, GI bleeding, ulceration, perforation.
* **Renal:** Renal impairment, acute kidney injury.
* **Cardiovascular:** Increased risk of serious cardiovascular thrombotic events (MI, stroke), hypertension, edema.
* **Hematologic:** Anemia, leukopenia.
* **Dermatologic:** Rash, pruritus.
* **Other:** Dizziness, headache, drowsiness, tinnitus.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
* **Diuretics and ACE inhibitors/ARBs:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels. Monitor lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects; concurrent use generally not recommended.
## Monitoring
* **Clinical:** Assess for pain relief, inflammation, and signs of adverse effects (GI bleeding, renal dysfunction, cardiovascular events).
* **Laboratory:** Consider baseline and periodic renal and hepatic function tests, complete blood count (CBC) with differential, especially with prolonged use or in at-risk patients.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* For dysmenorrhea, initiate treatment at the onset of pain or bleeding.
* Due to potential for serious GI events, use the lowest effective dose for the shortest duration necessary.
* Avoid concurrent use with other NSAIDs, including low-dose aspirin for cardioprotection, unless specifically advised by a prescriber.
**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete details and to verify accuracy before making treatment decisions.
