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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term management of mild to moderate pain. It acts by inhibiting prostaglandin synthesis.
## Primary Indications
* Pain associated with osteoarthritis and rheumatoid arthritis.
* Primary dysmenorrhea.
* Mild to moderate pain, including dental pain and post-operative pain.
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg every 8 hours as needed. Treatment should not exceed 7 days.
* **Rheumatoid Arthritis/Osteoarthritis:** 500 mg three times daily.
## Pediatric Dosing
Mefenamic acid is generally **not recommended for use in children under 14 years of age** due to insufficient safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment, though specific guidance is limited. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Patients with liver dysfunction may have altered drug metabolism. Monitor liver function.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria following aspirin or other NSAID administration.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Significant renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), dizziness, and drowsiness. Serious adverse effects include GI bleeding, ulceration, perforation, cardiovascular thrombotic events, renal failure, hepatic toxicity, and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
* **Other NSAIDs or Salicylates:** Increased risk of GI toxicity and other adverse effects.
* **ACE Inhibitors, ARBs, Diuretics:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* **GI bleeding:** Monitor for signs and symptoms (e.g., melena, hematemesis).
* **Renal function:** Monitor serum creatinine and BUN, especially in patients with risk factors for renal impairment.
* **Hepatic function:** Monitor liver enzymes (AST, ALT), especially with prolonged use or in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for potential increases.
* **Signs of cardiovascular events:** Monitor for new onset or worsening of symptoms.
## Clinical Pearls
* For dysmenorrhea, initiate treatment at the onset of menstrual pain and any associated symptoms (e.g., cramps) and continue for the duration of the symptoms, typically up to 7 days.
* Administer with food or milk to minimize GI upset.
* Avoid concurrent use with other NSAIDs or aspirin to minimize additive toxicity.
* Due to potential drowsiness, advise patients to exercise caution when driving or operating machinery.
* The maximum daily dose should not exceed 1500 mg for short-term use.
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**Disclaimer:** This information is intended for clinical use and does not replace professional judgment. Always consult the most current prescribing information, institutional protocols, and relevant literature before making clinical decisions.
