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# Mefenamic acid (meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class, primarily used for its analgesic and anti-inflammatory properties.
## Primary Indications
* Short-term management of mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum duration of use is typically 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours, starting at the onset of pain or bleeding and continuing for the duration of symptoms, not to exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for use in children under 14 years of age due to limited data and potential for adverse effects.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised. Mefenamic acid may be less suitable in severe impairment due to potential for renal and hepatic toxicity.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria induced by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Severe renal, hepatic, or cardiac impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Abdominal pain, nausea, vomiting, diarrhea, constipation, dyspepsia, dizziness, headache, drowsiness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including papillary necrosis); hepatotoxicity; cardiovascular thrombotic events; anaphylaxis; Stevens-Johnson syndrome/toxic epidermal necrolysis; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Other NSAIDs and Salicylates:** Increased risk of GI toxicity and renal toxicity.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
* **ACE Inhibitors and 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:** Monitor renal function tests periodically, especially in patients with risk factors for renal impairment.
* **Hepatic function:** Monitor liver function tests periodically.
* **Signs of GI bleeding:** Monitor for symptoms such as melena, hematemesis, or abdominal pain.
* **Blood pressure:** Monitor blood pressure, especially in patients taking antihypertensives.
## Clinical Pearls
* Mefenamic acid is indicated for **short-term use only.**
* Administer with food or milk to minimize GI upset.
* Use the lowest effective dose for the shortest possible duration to minimize risks.
* Consider NSAID-associated risks (GI, renal, cardiovascular) in all patients.
* Has a relatively short half-life, requiring frequent dosing.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the current prescribing information and relevant guidelines for complete and up-to-date drug details before making clinical decisions.
