Mefenamic-Acid, Oral Capsule

Why It’s Used

Mefenamic acid is used to treat mild to moderate pain and menstrual cramps. It’s approved to treat pain in people who are least 14 years old for no longer than 7 days. It’s approved to treat menstrual cramps for no longer than 2–3 days.

How It Works

Mefenamic acid belongs to a class of drugs called nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs help reduce pain, inflammation, and fever.

It isn’t known how this medication works to decrease pain. It may help reduce swelling by lowering levels of prostaglandin, a hormone-like substance that usually causes inflammation.

Mefenamic-Acid Side Effects

MOST COMMON SIDE EFFECTS

The most common side effects that occur with mefenamic acid include:

  • stomach pain
  • nausea
  • vomiting
  • heartburn
  • constipation
  • diarrhea
    • rash
  • dizziness
  • ringing in your ear (tinnitus)

Mild side effects may go away within a few days or a couple of weeks. Talk to your doctor or pharmacist if they’re more severe or don’t go away.

SERIOUS SIDE EFFECTS

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening or if you think you’re experiencing a medical emergency, call 9-1-1.

  • chest pain
  • shortness of breath
  • weakness on one side of your body
  • slurred speech
  • unusual weight gain
  • swelling in your arms, legs, hands, or feet
  • stomach pain or upset stomach
  • black, sticky stools
  • vomiting up blood
  • yellowing of your skin or whites of your eyes
  • flu-like symptoms, such as fever, chills, and body aches
  • tiredness
  • nausea
  • pain in the upper part of your stomach
  • itching
  • shortness of breath
  • swelling of your face, lips, or throat

Mefenamic-Acid May Interact with Other Medications

Mefenamic acid may interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Alcohol Interaction

Combining alcohol with mefenamic acid increases your risk of stomach bleeding or ulcer.

Medications That Might Interact with This Drug

Blood pressure drugs

Mefenamic acid may decrease the blood pressure-lowering effects of ACE inhibitors.

Diuretics (water pills)

Mefenamic acid can decrease the effectiveness of medications used to get rid of extra fluid in your body.

Nonsteriodal anti-inflammatory drugs

These include:

  • aspirin
  • ibuprofen
  • naproxen

Combining these medications may increase your risk of stomach bleeding and ulcers.

Anticoagulant, blood thinner

Taking both medications together increases your risk for serious stomach bleeding.

Bipolar disorder drug

Mefenamic acid may increase the amount of lithium in your body, which could be toxic. Your doctor may monitor for signs of lithium poisoning, such as nausea, vomiting, diarrhea, tremors, or confusion.

Disease-modifying antirheumatic drug

Mefenamic acid may increase the amount of methotrexate in your body, which may increase side effects of methotrexate.

Antacid

Magnesium hydroxide may increase mefenamic acid levels in your body, which could increase its side effects.

How to Take Mefenamic-Acid (Dosage)

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose
What Are You Taking This Medication For?

Mild to moderate pain

Form: Oral CapsuleStrength: 250 mg

Adult Dosage (ages 18 years and older) The first dose is 500 mg. After that, take 250 mg every 6 hours as needed. You shouldn’t take mefenamic acid for longer than 7 days.

Child Dosage (ages 14-17 years) The first dose is 500 mg. After that, take 250 mg every 6 hours as needed. You shouldn’t take mefenamic acid for longer than 7 days.

Child Dosage (ages 0-13 years) Dosage for people younger than 14 years hasn’t been established.

Menstrual pain

Form: Oral CapsuleStrength: 250 mg

Adult Dosage (ages 18 years and older)

  • Start this medication when your bleeding and symptoms start.
  • The first dose is 500 mg. After that, take 250 mg every 6 hours as needed.
  • You shouldn’t take mefenamic acid for longer than 3 days.

Child Dosage (ages 14-17 years)

  • Start this medication when your bleeding and symptoms start.
  • The first dose is 500 mg. After that, take 250 mg every 6 hours as needed.
  • You shouldn’t take mefenamic acid for longer than 2–3 days.

Child Dosage (ages 0-13 years) Dosage for people younger than 14 years hasn’t been established.

Special considerations Liver problems: If you have liver disease, your body might not be able to process this drug well. This may cause increased amounts of mefenamic acid in your blood and increase your risk of side effects. Your doctor may decrease your dose.

Kidney problems: If you have kidney disease, your body might not be able to clear out this drug as well as it should. This may cause increased amounts of mefenamic acid in your blood and increase your risk of side effects. Your doctor may decrease your dose.

Are There Any Alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

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