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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 primary dysmenorrhea. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain (e.g., dental pain, postpartum pain)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Do not exceed 1500 mg per day.
* **Primary Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain or bleeding. Do not exceed 1500 mg per day. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age due to limited safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduce dose and monitor renal function, especially in patients with pre-existing renal disease.
* **Hepatic Impairment:** Use with caution. Monitor liver function.
## 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 gastrointestinal (GI) bleeding or ulceration.
* Severe renal or hepatic impairment.
* Last trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal toxicity; hepatic toxicity; hypersensitivity reactions; Stevens-Johnson syndrome; toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI toxicity, renal toxicity, and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** May reduce antihypertensive effect and increase risk of renal toxicity.
* **Lithium:** May increase lithium levels.
* **Methotrexate:** May increase methotrexate levels and toxicity.
## Monitoring
* Renal function (BUN, creatinine)
* Liver function (AST, ALT)
* Complete blood count (CBC)
* Signs and symptoms of GI bleeding (e.g., melena, hematemesis)
* Blood pressure
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Use the lowest effective dose for the shortest possible duration.
* Discontinue if signs of GI bleeding, renal toxicity, or hepatic toxicity occur.
* Avoid concurrent use with other NSAIDs.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider to ensure the appropriateness of any medication for a specific patient.
