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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for short-term relief of mild to moderate pain. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing the synthesis of prostaglandins.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea).
* Pain associated with osteoarthritis and rheumatoid arthritis.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment duration should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 4-6 hours as needed, starting at the onset of bleeding and associated pain. Maximum daily dose is 1500 mg.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age for pain relief, except in specific cases of juvenile idiopathic arthritis where other NSAIDs are not suitable. Dosing for pediatric use in approved indications should be determined by a specialist and may follow protocols like 5-10 mg/kg/dose every 6-8 hours, not to exceed 50 mg/kg/day or adult maximums.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, however, caution is advised and lower doses may be considered in patients with severe impairment due to potential accumulation and increased risk of adverse effects.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, 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.
* Active gastrointestinal (GI) bleeding or history of recurrent GI ulceration/bleeding.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation, dizziness, and rash. Serious adverse effects can include GI bleeding, ulceration, perforation, cardiovascular thrombotic events (MI, stroke), renal failure, hepatic failure, severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis), and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **SSRIs and SNRIs:** Increased risk of GI bleeding.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **ACE inhibitors, ARBs, diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Other NSAIDs/Salicylates:** Increased risk of GI toxicity and reduced antipyretic effect of aspirin.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor blood pressure, as NSAIDs can elevate blood pressure.
* Assess for signs of hypersensitivity or severe skin reactions.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize GI upset.
* Diarrhea is a common and sometimes dose-limiting side effect.
* Due to potential for serious GI events, use the lowest effective dose for the shortest duration necessary.
* Consider the risks of cardiovascular and renal adverse events, particularly in elderly patients or those with risk factors.
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***Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions. Dosing and indications may vary based on local protocols and specific patient factors.*
