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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It possesses analgesic, anti-inflammatory, and antipyretic properties. Its mechanism of action involves the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 4000 mg per day.
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed, starting with the onset of pain and bleeding and continuing for the duration of the pain. Do not exceed 4000 mg per day.
* Treatment duration should generally not exceed 7 days for pain or 3 days for dysmenorrhea.
## Pediatric Dosing
* Mefenamic acid is generally not recommended for use in children under 14 years of age due to lack of established safety and efficacy.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Patients with pre-existing renal disease may be at increased risk. Dose reduction may be considered in severe impairment, but specific guidelines are lacking.
* **Hepatic Impairment:** Use with caution. Patients with hepatic impairment may be at increased risk of drug accumulation and toxicity. Dose reduction may be considered in severe impairment, but specific guidelines are lacking.
* **Elderly:** Consider a lower starting dose and more careful monitoring for adverse effects, particularly gastrointestinal bleeding and renal dysfunction.
## Contraindications
* Hypersensitivity to mefenamic acid 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.
* Significant renal impairment.
* Significant hepatic impairment.
* Severe heart failure.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, dyspepsia, flatulence.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal toxicity (acute kidney injury, interstitial nephritis); hepatotoxicity; hypersensitivity reactions (including anaphylaxis); Stevens-Johnson syndrome; toxic epidermal necrolysis; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal.
* **Diuretics and Antihypertensives:** May reduce their efficacy and increase risk of renal toxicity.
* **Lithium:** May increase serum lithium levels.
* **Methotrexate:** May increase methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis, abdominal pain).
* Monitor renal function (BUN, creatinine) especially in patients with pre-existing renal disease, elderly patients, or those on concomitant nephrotoxic agents.
* Monitor liver function (ALT, AST) especially in patients with hepatic impairment.
* Monitor for signs of cardiovascular events.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize gastrointestinal upset.
* Consider the lowest effective dose for the shortest duration necessary to minimize risks.
* Be aware of the increased risk of gastrointestinal bleeding, especially in the elderly or those with a history of ulcers.
* Mefenamic acid can increase blood pressure; monitor in patients with hypertension.
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**Disclaimer:** This information is intended for healthcare professionals and does not substitute for comprehensive drug information resources or clinical judgment. Always consult the most current prescribing information and relevant guidelines before initiating therapy.
