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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It acts by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* **Pain:** Short-term relief of mild to moderate pain, particularly associated with menstrual cramps (dysmenorrhea).
* **Inflammation:** Management of inflammatory conditions.
## Adult Dosing
* **Pain (Dysmenorrhea):** 500 mg every 6 hours, as needed.
* **Pain (Other):** 500 mg every 6 hours, as needed.
* **Maximum Daily Dose:** 1500 mg per day.
Treatment should generally not exceed 7 days.
## 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. Reduced doses may be considered, but data is limited. Avoid in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Reduced doses may be considered, but data is limited. Avoid in severe hepatic impairment.
* **Geriatric Patients:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal toxicity. Use with caution and consider the lowest effective dose.
## 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.
* Active or history of recurrent peptic ulcer or bleeding (two or more distinct episodes of documented ulceration or bleeding).
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Pregnancy, especially during the third trimester.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, gastrointestinal bleeding, ulceration.
* **Central Nervous System:** Dizziness, headache, drowsiness.
* **Renal:** Renal insufficiency, interstitial nephritis, papillary necrosis.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Dermatologic:** Rash, pruritus.
* **Cardiovascular:** Fluid retention, edema, hypertension. Increased risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
* **Diuretics and Antihypertensives:** May decrease efficacy and increase risk of renal toxicity.
* **Other NSAIDs and Salicylates:** Increased risk of adverse effects, particularly gastrointestinal.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis) and ulceration.
* **Renal Function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic Function:** Monitor liver function tests, especially with prolonged use or in patients with liver disease.
* **Blood Pressure:** Monitor blood pressure, particularly in patients with hypertension.
* **Electrolytes:** Monitor electrolytes, especially in patients with heart failure or renal impairment.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only due to the increased risk of gastrointestinal side effects with prolonged therapy.
* Administer with food or milk to reduce gastrointestinal upset.
* Mefenamic acid can mask signs of infection.
* The risk of cardiovascular thrombotic events is increased with NSAID use, including mefenamic acid.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions.*
