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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for short-term relief of mild to moderate pain, particularly menstrual pain.
## Primary Indications
* Pain (mild to moderate)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Not recommended for use for longer than 7 days.
* **Primary dysmenorrhea:** 500 mg every 6 hours starting at the onset of pain and bleeding, continuing for the duration of the pain (typically 2 to 3 days).
**Maximum Dose:** 1500 mg per day for self-medication; Prescriber-determined maximum of 1000 mg every 6 hours (4000 mg/day) in a clinical setting, though higher doses are generally not recommended due to increased risk of adverse events.
## Pediatric Dosing
Mefenamic acid is **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. No specific dosage adjustments are established, but dose reduction may be considered in severe impairment. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. No specific dosage adjustments are established. Monitor liver function.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, allergic rhinitis, or urticaria precipitated by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Severe heart failure.
* Active peptic ulceration or history of recurrent peptic ulceration.
* Cerebrovascular disease.
* Last trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, constipation, dizziness, and rash.
Serious adverse effects include gastrointestinal bleeding, perforation, ulceration, cardiovascular thrombotic events, renal toxicity, hepatic toxicity, hypersensitivity reactions, and bronchospasm.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of gastrointestinal bleeding.
* **Lithium:** Increased lithium levels, potential toxicity.
* **Methotrexate:** Increased methotrexate levels, potential toxicity.
* **Diuretics and antihypertensives:** May decrease their efficacy and increase risk of renal impairment.
## Monitoring
* **GI Symptoms:** Monitor for signs and symptoms of GI bleeding or ulceration (e.g., black tarry stools, hematemesis, abdominal pain).
* **Renal Function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic Function:** Monitor liver enzymes, especially in patients with pre-existing liver disease.
* **Blood Pressure:** Monitor blood pressure, as NSAIDs can cause fluid retention and hypertension.
* **Signs of Cardiovascular Events:** Educate patients on signs of MI or stroke.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only (up to 7 days) due to the risk of gastrointestinal and cardiovascular adverse events.
* Administer with food or milk to minimize gastrointestinal upset.
* The onset of analgesic effect is typically within 1 hour.
* Due to potential for dizziness and drowsiness, patients should exercise caution when driving or operating machinery.
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*Please verify the current prescribing information for complete details and any updates.*
