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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class. It has analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea), dental pain, and post-operative pain.
* Symptomatic relief of rheumatoid arthritis and osteoarthritis.
## Adult Dosing
* **Pain:** 500 mg every 6 to 8 hours as needed. Do not exceed 4000 mg in 24 hours.
* **Rheumatoid Arthritis/Osteoarthritis:** 250 mg to 500 mg every 6 to 8 hours. Do not exceed 4000 mg in 24 hours.
* Treatment duration for pain should generally not exceed 7 days.
## Pediatric Dosing
* Mefenamic acid is generally **not recommended** for children under 14 years of age.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduced doses may be necessary. Specific guidelines are not well established; monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Reduced doses may be necessary. Monitor liver function closely.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or history of recurrent GI ulceration or bleeding.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation, flatulence.
* **Serious:**
* GI bleeding, ulceration, perforation.
* Cardiovascular thrombotic events (MI, stroke).
* Renal failure and renal papillary necrosis.
* Hepatotoxicity.
* Hypersensitivity reactions (including anaphylaxis), Stevens-Johnson syndrome, toxic epidermal necrolysis.
* Exacerbation of asthma.
* Fluid retention and edema.
## 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.
* **Other NSAIDs / Aspirin:** Increased risk of GI adverse effects and potential for additive pharmacodynamic effects.
* **Diuretics / ACE Inhibitors / ARBs:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **GI symptoms:** Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* **Renal function:** Baseline and periodic monitoring of serum creatinine and BUN, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Baseline and periodic monitoring of liver function tests (AST, ALT), especially in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for increased blood pressure.
* **Cardiovascular risk:** Assess and monitor for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid is typically used for short-term pain management due to the risk of GI toxicity with prolonged use.
* Diarrhea is a common and sometimes dose-limiting side effect.
* Avoid concurrent use with other NSAIDs or aspirin unless specifically indicated and with increased caution.
* Consider gastroprotective agents (e.g., PPIs) in patients with increased GI risk factors.
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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 for any questions regarding medication use.*
