Mefenamic Acid (meftal-P)

# Mefenamic Acid (meftal-P) ## Overview Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exerts its effects by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis. ## Primary Indications * Short-term management of mild to moderate pain. * Primary dysmenorrhea. ## Adult Dosing * **Pain:** 500 mg orally every 6 hours as needed. Maximum daily dose is 1500 mg. * **Dysmenorrhea:** 500 mg orally every 6 hours starting with the onset of pain or bleeding and continuing for up to 3 days. ## Pediatric Dosing * **Pain and Dysmenorrhea (ages 14 to 18):** 500 mg orally every 6 hours as needed. Maximum daily dose is 1500 mg. * **Children under 14 years:** Safety and efficacy have not been established. ## Dose Adjustments * **Renal Impairment:** Use with caution. Data is limited; dose reduction may be considered in severe impairment, but specific guidance is lacking. * **Hepatic Impairment:** Use with caution. Data is limited; dose reduction may be considered in severe impairment, but specific guidance is lacking. ## Contraindications * Hypersensitivity to mefenamic acid 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. * Inflammatory bowel disease. * Severe renal or hepatic impairment. * Active gastrointestinal bleeding. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, headache, rash. * **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis); cardiovascular thrombotic events (myocardial infarction, stroke); hepatotoxicity; hypersensitivity reactions; exacerbation of asthma; 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):** Increased risk of gastrointestinal bleeding. * **Other NSAIDs/Aspirin:** Increased risk of adverse effects, particularly gastrointestinal bleeding. * **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** May reduce antihypertensive effect and increase risk of renal impairment. * **Lithium:** Increased serum lithium levels and risk of toxicity. * **Methotrexate:** Increased risk of methotrexate toxicity. ## Monitoring * **Renal function:** Particularly in patients with pre-existing renal disease or those receiving concomitant nephrotoxic agents. * **Hepatic function:** Especially in patients with liver disease or those on long-term therapy. * **Gastrointestinal symptoms:** Monitor for signs and symptoms of bleeding or ulceration. * **Blood pressure:** NSAIDs can increase blood pressure. ## Clinical Pearls * Mefenamic acid should be used for the shortest duration necessary to control symptoms. * Administer with food or milk to minimize gastrointestinal upset. * Due to its short half-life, it is typically dosed every 6 hours. * Consider the potential for NSAID-induced bronchospasm in patients with a history of asthma. * Be aware of the increased risk of cardiovascular events and gastrointestinal bleeding associated with NSAID use. *** **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 recommendations may vary based on individual patient factors and local protocols.