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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class, used for the short-term treatment of mild to moderate pain and for the relief of primary dysmenorrhea. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain (e.g., dental pain, post-operative pain)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 1500 mg in any 24-hour period for the first 7 days of treatment. For longer-term use, do not exceed 1000 mg every 4 to 6 hours.
* **Primary Dysmenorrhea:** 500 mg as the first dose, followed by 250 mg every 4 to 6 hours as needed. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited data and potential for adverse effects. If used, dosing should be guided by an experienced prescriber.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but reduced doses may be considered in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Data is limited.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease (active or history of).
* Severe heart failure.
* Concomitant use with other NSAIDs, including aspirin.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, and headache. Serious adverse effects include gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events (myocardial infarction, stroke), renal failure, hepatic failure, and severe skin reactions (e.g., 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) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding or perforation (e.g., melena, hematemesis, abdominal pain).
* Assess renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor blood pressure, particularly in patients with hypertension.
* Monitor for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Limit treatment duration to the shortest effective period, typically no more than 7 days.
* Due to potential for adverse effects, consider alternative analgesics if feasible, especially in elderly patients or those with comorbidities.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines for complete details before making any clinical decisions. Local protocols may vary.
