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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain. It works by inhibiting prostaglandin synthesis.
## Primary Indications
* Pain, including menstrual pain (dysmenorrhea) and pain associated with inflammation.
* Short-term relief of mild to moderate pain.
## Adult Dosing
* **Typical Dose:** 500 mg every 6 hours as needed.
* **Maximum Dose:** Not to exceed 1000 mg as a single dose or 4000 mg per day.
* Treatment should be limited to a maximum of 7 days.
## Pediatric Dosing
* **Children 14 years and older:** Same as adult dosing.
* **Children younger than 14 years:** Safety and efficacy have not been established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. Data is limited.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* 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 a history of recurrent gastrointestinal ulceration or bleeding.
* Severe renal or hepatic impairment.
* Severe heart failure.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis; bronchospasm (especially in aspirin-sensitive asthma).
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of gastrointestinal adverse effects and potentially additive renal effects.
* **ACE inhibitors and Angiotensin II Receptor Blockers (ARBs):** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic efficacy and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity. Monitor lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
## Monitoring
* **Gastrointestinal Symptoms:** Monitor for signs and symptoms of GI bleeding or ulceration.
* **Renal Function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those taking other nephrotoxic agents.
* **Hepatic Function:** Monitor liver enzymes, especially in patients with hepatic impairment.
* **Blood Pressure:** Monitor blood pressure, especially in patients with hypertension.
* **Cardiovascular Risk:** Assess for risk factors of cardiovascular events.
## Clinical Pearls
* Mefenamic acid is generally for short-term use only.
* Administer with food or milk to minimize gastrointestinal upset.
* Discontinue use immediately if signs of GI bleeding, rash, or hypersensitivity occur.
* Due to potential adverse effects, consider alternative analgesics if a patient has a history of peptic ulcer disease or GI bleeding.
**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols for complete details.
