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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties. Its mechanism of action involves the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* **Short-term relief of mild to moderate pain:** Including pain associated with dysmenorrhea, headache, dental pain, and post-operative pain.
* **Symptomatic treatment of rheumatoid arthritis and osteoarthritis:** Primarily for pain relief.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Rheumatoid arthritis/Osteoarthritis:** 500 mg three times daily, typically with food.
* **Maximum daily dose:** 1500 mg.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be guided by clinical judgment and specific product labeling. Some sources suggest doses similar to adult indications for children over 12 years of age.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is established, but reduce dose and monitor closely for adverse effects.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment is established, but reduce dose and monitor closely for adverse effects.
* **Geriatric Patients:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal issues. Use with caution and consider lower doses.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or history of recurrent gastrointestinal ulceration or hemorrhage.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, and dizziness. More serious adverse effects may include:
* **Gastrointestinal:** Gastric irritation, bleeding, ulceration, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Renal:** Renal papillary necrosis and other renal injury.
* **Hepatic:** Elevated liver enzymes, hepatitis.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Dermatologic:** Rash, pruritus.
* **Hypersensitivity:** Anaphylaxis, bronchospasm, angioedema.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **ACE Inhibitors, ARBs, Beta-blockers:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic effect and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
## Monitoring
* **Gastrointestinal symptoms:** Monitor for signs of bleeding (melena, hematemesis) or ulceration.
* **Renal function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those taking diuretics or ACE inhibitors.
* **Hepatic function:** Monitor liver enzymes, especially with prolonged use or in patients with hepatic impairment.
* **Blood pressure:** NSAIDs can cause or exacerbate hypertension.
* **Signs of hypersensitivity reactions.**
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use due to a higher risk of gastrointestinal adverse effects compared to some other NSAIDs.
* Administer with food or milk to minimize gastrointestinal upset.
* Avoid concurrent use with other NSAIDs or aspirin unless specifically indicated and monitored.
* Due to potential for dizziness, caution patients when operating machinery or driving.
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**Disclaimer:** This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions.
