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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties through the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Relief of rheumatoid arthritis and osteoarthritis symptoms.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose: 1500 mg.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, typically started at the onset of pain or bleeding. Maximum daily dose: 1500 mg.
* **Rheumatoid Arthritis/Osteoarthritis:** Dosing is highly individualized and should be determined by a healthcare provider. Typically, doses range from 500 mg to 750 mg three times daily, not exceeding 1500 mg per day.
**Important Note:** Mefenamic acid is intended for short-term use (usually not more than 7 days for pain). Long-term use should be carefully considered due to potential risks.
## Pediatric Dosing
Dosing for pediatric patients is not well-established and should be guided by a healthcare provider. If used, caution is advised, and lower doses may be appropriate. Some sources suggest doses of 6.5 mg/kg every 6 hours for children over 6 months, but this is not universally accepted and requires careful medical supervision.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary, and close monitoring is recommended. Mefenamic acid is contraindicated in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary, and close monitoring is recommended.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, 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 a history of recurrent gastrointestinal ulceration or bleeding.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* Central Nervous System: Dizziness, headache, drowsiness.
* Dermatologic: Rash, pruritus.
Serious adverse effects include:
* Cardiovascular: Increased risk of myocardial infarction, stroke, and heart failure.
* Gastrointestinal: Ulceration, bleeding, perforation.
* Renal: Renal papillary necrosis, interstitial nephritis, renal failure.
* Hepatic: Hepatitis, jaundice.
* Hematologic: Anemia, leukopenia, thrombocytopenia.
* Hypersensitivity reactions: Anaphylaxis, 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.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Diuretics and Antihypertensives:** May decrease their efficacy and increase the risk of renal impairment.
* **Lithium:** Mefenamic acid can increase serum lithium levels.
* **Methotrexate:** May increase methotrexate toxicity.
## Monitoring
* **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 with prolonged use or in patients with hepatic impairment.
* **Gastrointestinal symptoms:** Assess for signs of bleeding or ulceration.
* **Cardiovascular risk factors:** Advise patients of potential cardiovascular risks.
* **Bleeding:** Monitor for signs of bleeding, especially when used with anticoagulants or antiplatelet agents.
## Clinical Pearls
* Mefenamic acid is generally not recommended for chronic use due to its adverse effect profile, particularly gastrointestinal and cardiovascular risks.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Duration of use for pain should generally not exceed 7 days.
* Due to its short half-life, it is typically dosed every 6 hours.
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***Disclaimer:*** *This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information and guidelines for complete details before making any treatment decisions.*
