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## Mefenamic Acid
### Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain. It is also used for the treatment of primary dysmenorrhea.
### Primary Indications
* Mild to moderate pain
* Primary dysmenorrhea
### Adult Dosing
* **Pain:** 500 mg initially, followed by 250 mg every 6 hours as needed. Do not exceed 1000 mg per dose or 4000 mg per day.
* **Primary Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed, starting at the onset of pain and bleeding, and continuing for the duration of the pain. Do not exceed 1000 mg per day for more than 2 days.
### Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to insufficient data on safety and efficacy.
### Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are typically recommended, but close monitoring for adverse effects is advised.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are typically recommended, but close monitoring for adverse effects is advised.
### 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.
* Active gastrointestinal bleeding or a history of recurrent gastrointestinal ulceration or bleeding.
* Severe heart failure, renal impairment, or hepatic impairment.
### Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, dyspepsia, and constipation. More serious adverse effects can include gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events, renal failure, hepatic dysfunction, and hypersensitivity reactions.
### Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding and ulceration.
* **Diuretics and antihypertensives:** May reduce the efficacy of these agents and increase the risk of renal impairment.
* **Lithium:** May increase serum lithium levels. Monitor lithium levels.
* **Methotrexate:** May increase methotrexate toxicity.
* **Other NSAIDs and Salicylates:** Increased risk of adverse effects, particularly gastrointestinal toxicity.
### Monitoring
* Signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Renal function (BUN, creatinine) especially in patients with pre-existing renal disease or those at risk.
* Liver function (ALT, AST) if liver dysfunction is suspected.
* Blood pressure, especially in patients with hypertension.
### Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* It is intended for short-term use only. If symptoms persist beyond 7 days, re-evaluate the patient.
* Due to the risk of adverse cardiovascular thrombotic events, consider the indication and use the lowest effective dose for the shortest duration necessary.
* Be aware of the potential for pseudo-allergy in patients with aspirin sensitivity.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information or a qualified healthcare provider for complete and accurate drug information.*
