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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 inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term (up to 7 days) relief of mild to moderate pain including:
* Menstrual pain (dysmenorrhea)
* Headache
* Dental pain
* Postoperative pain
* Rheumatoid arthritis
* Osteoarthritis
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed, starting at the onset of pain and bleeding.
* **Rheumatoid Arthritis/Osteoarthritis:** 500 mg three times daily, or as directed by physician. The maximum dose should not exceed 1500 mg daily.
* Refer to local institutional guidelines or prescriber recommendations for specific dosing regimens.
## Pediatric Dosing
Mefenamic acid is **not recommended** for children under 14 years of age due to a lack of established safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary, particularly in severe impairment, based on individual patient response and renal function.
* **Hepatic Impairment:** Use with caution. Monitor liver function closely. Dose reduction may be warranted in severe hepatic impairment.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of gastrointestinal (GI) bleeding or perforation related to prior NSAID use.
* Active peptic ulceration or a history of recurrent peptic ulceration.
* Severe heart failure, renal impairment, or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, dizziness, headache, rash, pruritus.
* **Serious:**
* GI bleeding, ulceration, and perforation (can occur at any time, with or without warning symptoms).
* Cardiovascular thrombotic events (myocardial infarction, stroke).
* Renal toxicity (acute kidney injury, interstitial nephritis).
* Hepatotoxicity (elevated liver enzymes, hepatic failure).
* Hypersensitivity reactions (anaphylaxis, angioedema, Stevens-Johnson syndrome, toxic epidermal necrolysis).
* Hematologic effects (anemia, thrombocytopenia).
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **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 (including aspirin):** Increased risk of GI toxicity and additive pharmacologic effects.
* **Diuretics and Antihypertensives:** Decreased efficacy of antihypertensives; increased risk of nephrotoxicity.
* **Lithium:** Increased serum lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **GI symptoms:** Screen for signs and symptoms of GI bleeding or ulceration.
* **Renal function:** Monitor serum creatinine and urine output, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Monitor liver enzymes periodically, especially in patients with liver disease.
* **Blood pressure:** Monitor for potential increases.
* **Signs of hypersensitivity:** Observe for rash, difficulty breathing, or swelling.
## Clinical Pearls
* Mefenamic acid is generally indicated for short-term use only.
* Administer with food or milk to reduce GI upset.
* Avoid concurrent use with other NSAIDs.
* Patients with asthma may experience exacerbations triggered by NSAIDs.
* Consider lowest effective dose for the shortest duration necessary to minimize risks.
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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 clinical decisions.*
