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# Mefanic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea) and pain associated with dental procedures or minor surgery.
* Management of heavy menstrual bleeding.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain or bleeding and continuing for the duration of symptoms. Maximum daily dose is 1500 mg.
* **Heavy Menstrual Bleeding:** 500 mg three times daily for up to 5 days during menstruation.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to lack of established safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment. Specific guidelines vary.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment. Specific guidelines vary.
* **Elderly:** Increased risk of adverse effects. Use the lowest effective dose.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of NSAID-induced bronchospasm, urticaria, or allergic rhinitis.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or ulceration.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Gastrointestinal:** Dyspepsia, nausea, vomiting, diarrhea, constipation, abdominal pain, peptic ulceration, GI bleeding.
* **Central Nervous System:** Dizziness, headache, drowsiness.
* **Renal:** Renal dysfunction, interstitial nephritis.
* **Hematologic:** Thrombocytopenia, leukopenia, aplastic anemia (rare).
* **Dermatologic:** Rash, pruritus.
* **Other:** Bronchospasm (especially in asthmatics), fluid retention, edema.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Renal function:** Baseline and periodic monitoring of BUN and serum creatinine, especially in elderly patients or those with pre-existing renal disease.
* **Hepatic function:** Baseline and periodic monitoring of LFTs.
* **Gastrointestinal symptoms:** Monitor for signs of bleeding or ulceration.
* **Blood pressure:** Monitor for adequate blood pressure control, especially in patients taking antihypertensives.
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Limit duration of use to the shortest effective period to reduce the risk of adverse events.
* Be aware of the increased risk of cardiovascular thrombotic events associated with NSAID use (excluding aspirin).
* Should not be used concurrently with other NSAIDs.
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*Disclaimer: This information is intended for clinical pharmacists and healthcare professionals. Always consult the most current prescribing information and local protocols for definitive guidance.*
