Mefenamic Acid: Uses, Dose, Side Effects & Safe Use

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) often used for short-term pain, especially menstrual cramps. Want a simple guide on how to use it safely? Read on.

It reduces pain and inflammation by blocking prostaglandins. Doctors prescribe it for acute pain after surgery, dental pain, and primary dysmenorrhea (period pain). It isn’t meant for long-term use to manage chronic conditions.

Typical adult dosing starts with 500 mg as a single initial dose, then 250 mg every 6 hours as needed. Most guidelines limit total daily dose to 1,000 mg. For period cramps, treatment usually begins at the onset of pain and continues for up to three days. Children’s dosing and clinical situations vary—check a doctor.

Side effects and risks

Common side effects include stomach pain, heartburn, nausea, diarrhea, dizziness, and headache. Take mefenamic acid with food to reduce stomach upset.

Serious risks exist: gastrointestinal bleeding, ulcers, kidney problems, and increased blood pressure. Like other NSAIDs, long-term or high-dose use can raise the risk of heart attack or stroke, especially in people with heart disease.

Avoid mefenamic acid if you have an active peptic ulcer, significant kidney or liver disease, bleeding disorders, or a known allergy to NSAIDs. Don’t take it during the third trimester of pregnancy—it can harm the baby and delay labor.

Interactions and practical tips

Mefenamic acid can interact with blood thinners (warfarin), SSRIs, ACE inhibitors, diuretics, lithium, and methotrexate. Combining it with other NSAIDs or heavy alcohol increases bleeding risk.

Practical tips: take the lowest effective dose for the shortest time, always read the label, and don’t mix with other NSAIDs. If you’re over 65, have heart or kidney disease, or take multiple medications, check with your healthcare provider before using it.

If pain doesn’t improve in 48–72 hours or if you notice black stools, severe abdominal pain, sudden shortness of breath, swelling, or rash, stop the drug and seek medical help.

Alternatives include ibuprofen or naproxen for many pain types, acetaminophen for milder pain, and hormonal options for severe menstrual cramps. A clinician can suggest the best option based on your health.

Store mefenamic acid in a cool, dry place away from light and moisture, and keep it out of reach of children. Many countries require a prescription, so don’t assume online sellers are legitimate—use licensed pharmacies and check reviews. If you accidentally take more than the recommended dose, contact poison control or seek emergency care; symptoms of overdose include severe stomach pain, vomiting, drowsiness, or pale skin. Watch for allergic reactions like hives, swelling of the face or throat, or sudden breathing problems—these need immediate medical attention. Before surgery or dental work, tell the clinician you take mefenamic acid because it can affect bleeding. Keep a simple list of your medicines to share with any provider. Ask questions if anything feels unclear.

Want more on pain meds or safe pharmacy choices? Browse our guides or ask your pharmacist. Use medicines wisely—small changes like taking pills with food and checking interactions make a big difference.