Mefenamic Acid: NSAID for Pain and Inflammation

What is Mefenamic acid?

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class of medications. It is primarily used to treat mild to moderate pain, particularly menstrual pain, and to reduce inflammation and fever. This prescription medication works by blocking specific enzymes that cause pain and swelling in the body.

Uses

Mefenamic acid is approved for several pain-related conditions:

Menstrual pain (dysmenorrhea): One of the most common uses, providing relief from painful menstrual cramps and associated symptoms.

Mild to moderate pain: Effective for various types of acute pain including headaches, dental pain, and musculoskeletal pain.

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Inflammation reduction: Helps decrease swelling and inflammation associated with minor injuries or conditions like sprains.

Fever reduction: Can be used to lower elevated body temperature, though other medications are typically preferred for this purpose.

Short-term pain management: Often prescribed for temporary pain relief following minor surgical procedures or injuries.

How it works

Mefenamic acid works by inhibiting cyclooxygenase (COX) enzymes, specifically COX-1 and COX-2, which are responsible for producing prostaglandins. Prostaglandins are chemical messengers that promote inflammation, pain, and fever in the body. By blocking these enzymes, mefenamic acid reduces the production of prostaglandins, thereby decreasing pain, inflammation, and fever.

Side effects

Common side effects include:

• Stomach upset or nausea
• Diarrhea or loose stools
• Dizziness or drowsiness
• Headache
• Indigestion or heartburn
• Abdominal pain
• Skin rash or itching
• Nervousness or anxiety

Serious side effects requiring immediate medical attention:

• Severe stomach pain or black, tarry stools indicating gastrointestinal bleeding
• Chest pain, shortness of breath, or signs of heart problems
• Severe skin reactions including blistering or peeling
• Signs of kidney problems such as decreased urination or swelling
• Severe allergic reactions including difficulty breathing or facial swelling

Warnings and precautions

Mefenamic acid carries several important safety considerations. Patients with a history of stomach ulcers, bleeding disorders, or severe kidney or liver disease should avoid this medication. The drug increases the risk of serious cardiovascular events, including heart attack and stroke, particularly with long-term use or in patients with existing heart disease.

Pregnant women should not use mefenamic acid, especially during the third trimester, as it may cause complications for both mother and baby, including premature closure of the ductus arteriosus in the fetus. Elderly patients require careful monitoring as they have increased risk of serious side effects, particularly gastrointestinal bleeding and kidney problems.

Patients should take mefenamic acid with food to reduce stomach irritation, and treatment duration should be limited to the shortest time necessary for symptom relief, typically not exceeding seven days for acute conditions.

Interactions

Mefenamic acid can interact with numerous medications, potentially altering their effectiveness or increasing side effect risks:

Warfarin and other blood thinners: Increased bleeding risk due to enhanced anticoagulant effects and potential gastrointestinal irritation.

ACE inhibitors and ARBs: Reduced effectiveness of blood pressure medications and increased risk of kidney problems.

Lithium: Elevated lithium blood levels, potentially leading to lithium toxicity.

Methotrexate: Increased methotrexate levels and toxicity risk, particularly affecting kidney function.

Diuretics: Reduced effectiveness of water pills and increased risk of kidney dysfunction.

Aspirin: Increased risk of stomach bleeding and reduced cardiovascular protective effects of low-dose aspirin.

Corticosteroids: Significantly increased risk of gastrointestinal bleeding and ulceration.

Alcohol: Enhanced risk of stomach bleeding and liver damage when used regularly.

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Dosage

For adults, the typical starting dose of mefenamic acid is 500 mg initially, followed by 250 mg every 6 hours as needed for pain relief. The maximum recommended daily dose should not exceed 1250 mg. For menstrual pain, treatment usually begins at the onset of bleeding and continues for 2-3 days or until symptoms subside.

Treatment duration should be limited to no more than seven days for acute conditions due to increased risk of side effects with prolonged use. Dosage adjustments may be necessary for patients with kidney impairment or elderly individuals. Always follow your healthcare provider’s specific dosing instructions, as individual needs may vary based on the condition being treated and patient factors.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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