1. Mefenamic acid oral capsule is available as a generic drug and a brand-name drug. Brand name: Ponstel.
  2. Mefenamic acid only comes as a capsule you take by mouth.
  3. Mefenamic acid oral capsule is used to treat mild to moderate pain and dysmenorrhea (menstrual pain).

Mefenamic acid is a prescription drug. It only comes as an oral capsule.

Mefenamic acid oral capsule is available as the brand-name drug Ponstel. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in all strengths or forms as the brand-name drug.

Why it’s used

Mefenamic acid is used to treat mild to moderate pain and dysmenorrhea (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 two to three 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 oral capsule doesn’t cause drowsiness. However, it can cause other side effects.

More common side effects

The more common side effects that can occur with mefenamic acid include:

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

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

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re experiencing a medical emergency. Serious side effects and their symptoms can include the following:

  • Heart attack or stroke. Symptoms may include:
    • chest pain
    • shortness of breath
    • weakness on one side of your body
    • slurred speech
  • Heart failure. Symptoms may include:
    • unusual weight gain
    • swelling in your arms, legs, hands, or feet
  • Stomach problems, such as ulcers or bleeding. Symptoms may include:
    • stomach pain or upset stomach
    • black, sticky stools
    • vomiting up blood
  • Liver problems. Symptoms may include:
    • 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
  • Skin reactions. Symptoms may include:
    • reddening, blistering, or peeling skin

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Mefenamic acid oral capsule may interact with other medications, herbs, or vitamins you might be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out 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.

Examples of drugs that can cause interactions with mefenamic acid are listed below.

Blood pressure drugs

Taking these drugs with mefenamic acid may decrease their blood pressure-lowering effects. Examples of these drugs include:

  • angiotensin-converting enzyme (ACE) inhibitors, such as:
    • valsartan
    • candesartan
    • losartan
  • angiotensin receptor blockers, such as:
    • captopril
    • lisinopril
    • enalapril
  • beta-blockers, such as:
    • metoprolol
    • atenolol
    • timolol

Diuretics (water pills)

Taking these drugs with mefenamic acid can decrease their effectiveness. This means they won’t work as well to get rid of extra fluid in your body. Examples of these drugs include:

  • chlorthalidone
  • torsemide
  • bumetanide

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Taking NSAIDs with mefenamic acid may increase your risk of stomach bleeding and ulcers. Examples of these drugs include:

  • aspirin
  • ibuprofen
  • naproxen

Anticoagulant/blood thinner

Taking warfarin with mefenamic acid increases your risk of serious stomach bleeding.

Drugs that affect serotonin

Taking selective serotonin reuptake inhibitors (SSRIs) with mefenamic acid increases your risk of serious stomach bleeding. Examples of these drugs include:

  • citalopram
  • fluoxetine
  • sertraline

Bipolar disorder drug

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

Disease-modifying antirheumatic drug

Taking methotrexate with mefenamic acid may increase the amount of methotrexate in your body. This may increase side effects from methotrexate.

Antacid

Taking magnesium hydroxide (milk of magnesia) with mefenamic acid may increase mefenamic acid levels in your body. This could increase its side effects.

Digoxin

If you take mefenamic acid with digoxin, it may increase the digoxin in your body to harmful levels.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you’re taking.

This dosage information is for mefenamic acid oral capsule. 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
  • the severity of your condition
  • other medical conditions you have
  • how you react to the first dose

Forms and strengths

Generic: Mefenamic acid

  • Form: oral capsule
  • Strength: 250 mg

Brand: Ponstel

  • Form: oral capsule
  • Strength: 250 mg

Dosage for mild to moderate pain

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 seven days.

Child dosage (ages 0–13 years)

Dosage for people younger than 14 years hasn’t been established.

Dosage for menstrual pain

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 three 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 two to three days.

Child dosage (ages 0–13 years)

Dosage for people younger than 14 years hasn’t been established.

Special dosing considerations

For people with 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 prescribe a decreased dosage.

For people with 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 prescribe a decreased dosage.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

FDA warnings: Potentially fatal heart risks and stomach problems

  • This drug has a black box warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients about drug effects that may be dangerous.
  • Heart risk warning: Mefenamic acid may increase your risk of heart problems, including blood clot, heart attack, stroke, or heart failure. These conditions can be fatal. Your risk may increase if you already have heart disease or have taken mefenamic acid for a long period of time or at high doses. You shouldn’t take mefenamic acid to treat pain before a coronary bypass graft surgery. This is a heart surgery that’s done to increase blood flow to your heart. Taking mefenamic acid around the time of your surgery will increase your risk of heart attack and stroke.
  • Stomach problem warning: Mefenamic acid may increase your risk of stomach problems, such as bleeding, or peptic ulcers (small holes in the lining of your stomach or intestines). These conditions can be fatal. They can occur at any time and without any warning signs or symptoms. If you’re aged 65 years or older, you may have a greater chance for severe stomach issues.

Liver damage warning

Mefenamic acid may damage your liver. Your doctor may take a blood test to monitor your liver and make sure this drug is safe for you. Call your doctor immediately if you notice symptoms of liver damage, such as:

  • nausea
  • tiredness
  • itching
  • yellowing of your skin or whites or your eyes
  • pain in your upper stomach
  • flu-like symptoms, such as fever, chills, and body aches

Dangerous skin reactions warning

Get emergency medical help right away if you experience:

  • a severe skin reaction
  • rash that is red, swollen, peeling, or blistered

This might be a severe skin disorder such as exfoliative dermatitis, Stevens-Johnson syndrome, or toxic epidermal necrolysis, all of which can be fatal.

Pregnancy warning

You shouldn’t use mefenamic acid in the third trimester of pregnancy. It may cause the blood vessel that supplies nutrients and oxygen to the fetus to close too early.

Allergy warning

Mefenamic acid can cause a severe allergic reaction. Symptoms may include:

  • trouble breathing
  • swelling of your face or throat
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal.

Don’t take this medication if you’re allergic to aspirin or other NSAIDs. These include ibuprofen, naproxen, diclofenac, and meloxicam.

Alcohol interaction warning

Consuming drinks that contain alcohol with mefenamic acid increases your risk of stomach bleeding or ulcer.

Warnings for people with certain health conditions

For people with heart disease, including heart failure and high blood pressure: Mefenamic acid may cause an increased risk of heart problems, including heart attack, stroke, or blood clot. Your risk may be higher if you already have heart disease and take this medication for a longer period of time. Mefenamic acid may cause you to retain water and can make high blood pressure worse or increase your risk of heart failure.

For people with ulcers and stomach bleeding: Mefenamic acid increases your risk of bleeding or ulcers in your stomach or intestines. These can occur at any time and without any warning signs or symptoms. You’re at a greater risk for serious stomach and intestinal bleeding if you’re older than 65 years, drink alcohol, or smoke cigarettes. Tell your doctor if you currently have stomach ulcer or bleeding, or if you’ve had one in the past.

For people with asthma: Mefenamic acid may cause your airways to become narrower or smaller, which can be deadly. If your asthma gets worse, get emergency medical help. If you have asthma that’s sensitive to aspirin or NSAIDs, you shouldn’t take this medication at all.

For people with kidney disease: Mefenamic acid can damage your kidneys if you take it for a long period of time. Tell your doctor if you have a history of kidney disease.

Warnings for other groups

For pregnant women: Mefenamic acid has not been sufficiently studied in pregnant women. If you’re pregnant or plan to become pregnant, talk to your doctor about whether this drug is safe for you.

Women who are breastfeeding: Small amounts of mefenamic acid may be passed into your breast milk and cause side effects in your child. You and your doctor may need to decide whether you’ll stop breastfeeding or stop taking mefenamic acid.

For seniors: If you’re older than 65 years, your body may clear this drug more slowly. This can lead to a buildup of the drug in your body and increase your risk of side effects. Your doctor may monitor your kidneys while you take mefenamic acid to make sure it’s still safe for you.

For children: The safety and effectiveness of mefenamic acid haven’t been established in people younger than 14 years.

Mefenamic acid oral capsule is used for short-term treatment. If you’re using it for mild to moderate pain, treatment usually lasts no longer than seven days. If you’re using it for menstrual cramps, treatment usually lasts no longer than two to three days. This drug comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug or don’t take it at all: Your pain may not be relieved.

If you miss doses or don’t take the drug on schedule: Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much: If you take too much mefenamic acid, you may experience:

  • drowsiness
  • nausea
  • vomiting
  • stomach pain
  • stomach bleeding
  • high blood pressure
  • kidney failure
  • slowed breathing
  • coma

If you think you’ve taken too much of this drug, call your doctor or seek guidance from the American Association of Poison Control Centers at 1-800-222-1222 or through their online tool. But if your symptoms are severe, call 911 or go to the nearest emergency room right away.

What to do if you miss a dose: This medication is taken every six hours as needed. If you planned to take it and missed a dose, take it as soon as you can. After you take it, wait another six hours for the next dose. Don’t take more than one capsule to make up for a missed dose. This could result in dangerous side effects.

How to tell if the drug is working: You should experience less pain.

Keep these considerations in mind if your doctor prescribes mefenamic acid oral capsule for you.

General

  • You can take mefenamic acid with food to avoid upset stomach.
  • Don’t crush or chew the oral capsule. Swallow it whole.

Storage

  • Store mefenamic acid at room temperature between 68°F and 77°F (20°C and 25°C).
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport X-ray machines. They won’t damage your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

While you take this drug, your doctor may perform:

  • blood tests to check for possible bleeding.
  • liver function tests to make sure mefenamic acid isn’t harming your liver.
  • kidney function tests to make sure mefenamic acid isn’t harming your kidneys.

Availability

Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead to make sure your pharmacy carries it.

Prior authorization

Many insurance companies require a prior authorization for this drug. This means your doctor will need to get approval from your insurance company before your insurance company will pay for the prescription.

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.