Please check your internet connection and try again.
# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic and anti-inflammatory properties. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Relief of mild to moderate pain, including menstrual pain (dysmenorrhea), headache, and pain associated with musculoskeletal disorders.
* Management of inflammation.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain and bleeding.
* **Maximum:** 1500 mg per day for short-term use. Do not exceed 7 days of continuous use without medical supervision.
## Pediatric Dosing
* **Age 14 years and older:** Same as adult dosing.
* **Younger than 14 years:** Dosing has not been established. Use in this population is generally not recommended due to lack of safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be considered in severe renal impairment, though specific guidance is lacking. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Dose reduction may be considered in severe hepatic impairment, though specific guidance is lacking. Monitor liver function closely.
* **Elderly:** May be more susceptible to adverse effects, particularly gastrointestinal bleeding and renal toxicity. Consider lower doses and shorter duration of therapy.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, 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 history of recurrent gastrointestinal ulceration or bleeding.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, drowsiness, headache.
* **Serious:**
* **Gastrointestinal:** Ulceration, bleeding, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction and stroke, hypertension.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Other:** Bronchospasm (especially in aspirin-sensitive asthma), fluid retention, edema.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin, heparin):** Increased risk of bleeding. Monitor INR closely.
* **Antiplatelet agents (e.g., aspirin, clopidogrel):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Diuretics:** Reduced diuretic efficacy, increased risk of nephrotoxicity.
* **Lithium:** Increased lithium levels and risk of toxicity. Monitor lithium levels.
* **Methotrexate:** Increased methotrexate levels and risk of toxicity.
* **ACE inhibitors and Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive effect, increased risk of renal impairment.
* **Cyclosporine and Tacrolimus:** Increased risk of nephrotoxicity.
## Monitoring
* **Renal function:** Serum creatinine and BUN, especially in patients with pre-existing renal disease, elderly patients, or those on concomitant nephrotoxic drugs.
* **Hepatic function:** Liver enzymes (ALT, AST), especially in patients with hepatic impairment or those on long-term therapy.
* **Gastrointestinal symptoms:** Monitor for signs of bleeding (e.g., melena, hematemesis, abdominal pain).
* **Blood pressure:** Especially in patients with hypertension or those taking antihypertensives.
* **Signs of hypersensitivity reactions.**
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only.
* Take with food or milk to minimize gastrointestinal upset.
* Advise patients to report any signs of bleeding, such as black, tarry stools or vomiting blood.
* Avoid concurrent use with other NSAIDs, including aspirin, unless specifically indicated for cardioprotection at a low dose, and even then, exercise caution due to increased GI risk.
* Due to potential for drowsiness and dizziness, advise caution when operating machinery or driving.
***
**Disclaimer:** This information is intended for healthcare professionals and does not replace comprehensive prescribing information. Always consult the most current drug product labeling and local protocols before prescribing or administering medications.
