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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivatives class. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Management of mild to moderate pain, particularly associated with menstrual cramps (dysmenorrhea).
* Relief of pain and inflammation in conditions like rheumatoid arthritis and osteoarthritis (though generally not a first-line agent for chronic conditions).
## Adult Dosing
* **Dysmenorrhea:** 500 mg every 4 hours as needed, not to exceed 1250 mg per day.
* **Mild to moderate pain:** 500 mg every 4 hours as needed, not to exceed 1250 mg per day.
* **Rheumatoid arthritis/Osteoarthritis:** 500 mg three times daily. Maximum daily dose should not exceed 1500 mg.
## Pediatric Dosing
Mefenamic acid is **not generally recommended** for use in children under 14 years of age. Specific pediatric dosing is not well-established.
## 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.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria following aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or a history of recurrent GI ulceration/bleeding.
* Severe renal or hepatic impairment.
* Pregnancy: Particularly in the third trimester.
## Adverse Effects
Common:
* GI upset (nausea, vomiting, diarrhea, abdominal pain)
* Headache
* Dizziness
* Drowsiness
Serious:
* GI ulceration, bleeding, and perforation
* Cardiovascular thrombotic events (myocardial infarction, stroke)
* Renal toxicity (interstitial nephritis, papillary necrosis)
* Hepatic injury
* Hypersensitivity reactions (including Stevens-Johnson syndrome, toxic epidermal necrolysis)
* Exacerbation of asthma
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics, ACE inhibitors, ARBs:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Lithium:** Increased lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
* **Other NSAIDs:** Increased risk of GI, renal, and cardiovascular side effects.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those taking diuretics/ACE inhibitors.
* **Hepatic function:** Especially in patients with pre-existing liver disease.
* **Signs and symptoms of GI bleeding:** Monitor for melena, hematemesis, or abdominal pain.
* **Blood pressure:** NSAIDs can increase blood pressure.
## Clinical Pearls
* Mefenamic acid has a relatively short duration of action and is typically used for short-term pain management.
* It is generally recommended to take mefenamic acid with food or milk to minimize GI upset.
* Due to potential serious adverse effects, consider the lowest effective dose for the shortest duration necessary.
* Avoid concurrent use with other NSAIDs.
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*Disclaimer: This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant guidelines for definitive patient management decisions. Dosing and recommendations may vary based on local protocols and individual patient factors.*
