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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term treatment of mild to moderate pain and for the relief of menstrual pain. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 4-6 hours as needed. Do not exceed 1500 mg in 24 hours.
* **Primary dysmenorrhea:** 500 mg every 4-6 hours as needed, starting with the onset of pain and bleeding, and continuing for the duration of symptoms. Do not exceed 1500 mg in 24 hours.
* **Maximum Duration:** Treatment should not exceed 7 days for pain or 3 days for dysmenorrhea without medical advice.
## 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 data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal events. Consider a lower dose.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of bronchospasm, asthma, rhinitis, 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 history of recurrent gastrointestinal bleeding.
* Severe renal, hepatic, or cardiac impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation, rash.
* **Serious:**
* **Gastrointestinal:** Bleeding, ulceration, perforation.
* **Cardiovascular:** Myocardial infarction, stroke, hypertension.
* **Renal:** Acute kidney injury, interstitial nephritis.
* **Hepatic:** Liver enzyme elevations, hepatitis.
* **Hematologic:** Anemia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, angioedema, severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).
* **Respiratory:** Bronchospasm, asthma exacerbation.
## 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 / Aspirin:** Increased risk of adverse effects, especially gastrointestinal bleeding.
* **Diuretics / ACE Inhibitors / ARBs:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
## Monitoring
* **Gastrointestinal:** Signs and symptoms of bleeding (e.g., melena, hematemesis), abdominal pain.
* **Renal Function:** Serum creatinine, BUN, especially in patients with pre-existing renal disease or risk factors.
* **Hepatic Function:** Liver function tests, especially in patients with liver disease or risk factors.
* **Cardiovascular Risk:** Blood pressure.
* **Signs of Hypersensitivity:** Monitor for rash, pruritus, difficulty breathing.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Use the lowest effective dose for the shortest duration necessary to minimize risks.
* Advise patients to avoid concurrent use of other NSAIDs, including aspirin.
* Educate patients on the signs and symptoms of serious adverse effects, particularly gastrointestinal bleeding and cardiovascular events.
* Mefenamic acid is associated with a higher incidence of diarrhea compared to some other NSAIDs.
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*This information is intended for healthcare professionals. It is crucial to consult the most current prescribing information and relevant guidelines for complete details before making any clinical decisions. This information does not replace professional medical advice.*
