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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term management of mild to moderate pain. It is also known by brand names such as Ponstel.
## Primary Indications
* Short-term relief of mild to moderate pain, including:
* Menstrual pain (dysmenorrhea)
* Headache
* Toothache
* Muscle pain
* Surgical pain
## Adult Dosing
* **Initial Dose:** 500 mg orally every 6 hours as needed.
* **Maximum Daily Dose:** 1500 mg orally per day.
* **Duration of Therapy:** Typically limited to 7 days or less.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited safety and efficacy data. However, some sources suggest a dose of 6.5 mg/kg orally every 6 hours, not to exceed 500 mg per dose or 1500 mg per day, for children 14 years and older. Specific pediatric dosing should be determined by a healthcare provider based on weight and clinical indication.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
## 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 bleeding or history of recurrent gastrointestinal bleeding.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, headache, dizziness.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## 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.
* **ACE inhibitors/ARBs:** May decrease antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May decrease diuretic effect and increase risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (melena, hematemesis, abdominal pain).
* **Renal Function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* **Hepatic Function:** Monitor liver function tests (LFTs), especially with prolonged use or in patients with hepatic impairment.
* **Cardiovascular:** Assess risk factors for cardiovascular disease.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for gastrointestinal toxicity, it is generally reserved for short-term use.
* For dysmenorrhea, it is often recommended to start treatment at the onset of pain or bleeding, or even a day before, and continue for the duration of the pain.
* Avoid concurrent use with other NSAIDs to minimize additive toxicity.
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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 relevant guidelines before making any clinical decisions.*
