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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain and bleeding and continuing for the duration of the symptoms. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is not generally recommended for children under 14 years of age due to lack of established safety and efficacy data. Some sources may suggest dosing for specific indications in older children, but this is not standard.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be necessary in severe renal impairment. Avoid if CrCl is significantly reduced.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be necessary in severe hepatic impairment.
## Contraindications
* Known 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.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions (including anaphylaxis); 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.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **ACE inhibitors, ARBs, diuretics:** Reduced antihypertensive effect; increased risk of renal dysfunction.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
## Monitoring
* **GI bleeding:** Monitor for signs and symptoms (e.g., melena, hematemesis).
* **Renal function:** Baseline and periodic assessment of BUN, creatinine, and urine output, especially in patients with risk factors for renal impairment.
* **Hepatic function:** Baseline and periodic assessment of LFTs, especially in patients with pre-existing liver disease.
* **Cardiovascular risk:** Counsel patients on signs of cardiovascular events.
* **Blood pressure:** Monitor for potential increases.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize gastric irritation.
* Risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke can occur anytime during treatment.
* NSAIDs, including mefenamic acid, can cause serious GI bleeding, ulceration, and perforation. Risk increases with higher doses and longer duration of use.
* Use the lowest effective dose for the shortest duration necessary.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and local guidelines before administering any medication. Dosing and indications may vary.*
