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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic and anti-inflammatory properties. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Do not exceed 1500 mg in the first 24 hours of treatment, and do not exceed 1000 mg in any 24-hour period thereafter.
* **Primary Dysmenorrhea:** 500 mg every 6 hours, starting at the onset of pain or bleeding, whichever comes first. Treatment should not exceed 6 days per month.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age due to insufficient data regarding safety and efficacy.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment. Specific guidelines are not well-established.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment. Specific guidelines are not well-established.
* **Elderly:** Increased risk of adverse effects. Consider using the lowest effective dose.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of bronchospasm, 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 (GI) bleeding or history of recurrent GI bleeding.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Pregnancy, particularly in the third trimester.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, dizziness, headache, rash.
* **Serious:** GI bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal failure; hepatic failure; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
* **ACE inhibitors, ARBs, Beta-blockers:** Reduced antihypertensive effect; increased risk of renal dysfunction.
* **Diuretics:** Reduced diuretic and antihypertensive effect; increased risk of renal dysfunction.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **GI bleeding:** Monitor for signs and symptoms (e.g., melena, hematemesis, abdominal pain).
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* **Hepatic function:** Monitor LFTs, especially in patients with pre-existing liver disease.
* **Cardiovascular risk:** Assess and manage risk factors.
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Limit duration of use to the shortest effective period.
* Avoid concomitant use with other NSAIDs.
* Should not be used in patients with aspirin-sensitive asthma.
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**Disclaimer:** This information is intended for clinical pharmacists and healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for definitive patient management decisions. Dosing and recommendations may vary based on individual patient factors and local institutional protocols.
