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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.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea).
* Pain associated with dental procedures.
* Pain and inflammation from musculoskeletal disorders.
## Adult Dosing
* **Pain:** 500 mg every 6-8 hours as needed.
* **Dysmenorrhea:** 500 mg every 6-8 hours as needed, usually starting with the onset of pain and bleeding.
* **Maximum Dose:** 1500 mg per day. A course of treatment should not exceed 7 days.
## Pediatric Dosing
* Mefenamic acid is generally not recommended for children under 14 years of age due to lack of established safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment. Monitor hepatic function closely.
* **Elderly:** May be more susceptible to adverse effects; consider lower doses and monitor closely.
## Contraindications
* 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, ulceration, or perforation.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, headache, dizziness, rash.
* **Serious:**
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and new-onset or worsening hypertension.
* **Gastrointestinal:** Serious GI bleeding, ulceration, perforation.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Hepatitis, jaundice.
* **Hematologic:** Anemia, thrombocytopenia, leukopenia.
* **Dermatologic:** Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Hypersensitivity:** Anaphylaxis, angioedema, bronchospasm.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI toxicity and other adverse effects.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* **Renal Function:** Serum creatinine, BUN, especially in patients with pre-existing renal disease or those taking diuretics or ACE inhibitors.
* **Hepatic Function:** Liver enzymes (ALT, AST), bilirubin, especially in patients with pre-existing hepatic disease.
* **Gastrointestinal Symptoms:** Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* **Blood Pressure:** Monitor for new-onset or worsening hypertension.
* **Signs of Cardiovascular Events:** Educate patients to report chest pain, shortness of breath, weakness, or slurred speech.
* **Signs of Hypersensitivity Reactions:** Monitor for rash, itching, swelling, difficulty breathing.
## Clinical Pearls
* Mefenamic acid should be used at the lowest effective dose for the shortest duration necessary to minimize risks.
* Administer with food or milk to reduce GI upset.
* Avoid concomitant use with other NSAIDs.
* Discontinue use if signs of GI bleeding, cardiovascular events, or severe adverse reactions occur.
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**Disclaimer:** This information is intended for healthcare professionals. Please consult the most current prescribing information or a reliable drug reference for complete details and to verify information before making clinical decisions.
