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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It acts by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg every 6 hours as needed.
* **Maximum:** Not to exceed 1500 mg per day for self-medication or 3000 mg per day under physician supervision for a limited duration. Duration of use should not exceed 7 days for pain or 3 days for fever.
## Pediatric Dosing
* **Pain/Fever:** Mefenamic acid is generally **not recommended** for children under 14 years of age unless specifically indicated and directed by a physician. When used for fever, doses of **6.5 mg/kg every 6-8 hours** have been suggested, usually not exceeding 4 doses in 24 hours. Maximum duration for fever is typically 3 days.
* **Uncertainty:** Pediatric dosing is not as well-established as for adults. Dosing and duration must be carefully considered based on age, weight, and clinical indication.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment, though specific guidelines are not well-defined.
* **Hepatic Impairment:** Use with caution. Dose reduction may be considered, especially in severe hepatic impairment.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of gastrointestinal (GI) bleeding or perforation related to prior NSAID use.
* Active peptic ulceration or history of recurrent peptic ulceration.
* Severe heart failure, renal impairment, or hepatic impairment.
* Concomitant use with other NSAIDs or anticoagulants (relative contraindication).
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Dyspepsia, nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, headache.
* **Serious:** GI bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis); cardiovascular thrombotic events (MI, stroke); hepatic reactions; hypersensitivity reactions; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs/Aspirin:** Increased risk of GI toxicity and reduced antiplatelet effect of low-dose aspirin.
* **ACE inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium/Methotrexate:** Increased serum concentration and toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
## Monitoring
* **GI Symptoms:** Monitor for signs and symptoms of GI bleeding or ulceration (e.g., melena, hematemesis).
* **Renal Function:** Baseline and periodic assessment of renal function, especially in patients with pre-existing renal disease or those on concurrent nephrotoxic agents.
* **Hepatic Function:** Baseline and periodic assessment of hepatic function, especially in patients with liver disease.
* **Blood Pressure:** Monitor blood pressure, particularly in patients with hypertension.
## Clinical Pearls
* Mefenamic acid is generally intended for short-term use only.
* Administer with food or milk to minimize GI upset.
* The risk of GI adverse events increases with dose and duration of therapy.
* It is less potent and has a shorter duration of action compared to some other NSAIDs, necessitating more frequent dosing.
* Caution is advised in elderly patients due to increased risk of adverse effects, particularly GI bleeding and renal toxicity.
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*Disclaimer: This information is intended for clinical use and does not replace a thorough review of the manufacturer's prescribing information or consultation with a medical professional. Always verify current dosing, indications, contraindications, and safety information before prescribing.*
