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Mefenamic Acid (Pain Reliever, NSAID)

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jul 21, 2022

Mefenamic acid is part of the drug class called nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs like mefenamic acid are used to treat mild to moderate pain. It can be purchased over-the-counter without a prescription.

mefenamic acid

Know the basics

What is mefenamic acid used for?

  • Short-term pain management
  • Headache
  • Menstrual pain, dysmenorrhea
  • Muscle and joint pain
  • Pain and inflammation
  • Post-surgery pain
  • How should I take mefenamic acid?

    Read the directions on the packaging for complete information. Check the label and expiration date.

    For oral dosage forms, swallow it whole without chewing, crushing, or dissolving it in liquid. Take it with meals to prevent gastric irritation.

    How do I store mefenamic acid?

    This product is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer. 

    There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

    You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

    Know the precautions & warnings

    What should I know before using mefenamic acid?

    Before using this drug, tell your doctor if you are/have:

    • Pregnant or breastfeeding
    • Taking any other medicines. This includes any prescription, OTC, and herbal remedies.
    • An allergy to any of the ingredients of this product
    • Any other illnesses, disorders, or medical conditions

    Is it safe to take mefenamic acid during pregnancy or breastfeeding?

    Unfortunately, there isn’t enough information about the safety of using this drug during pregnancy and breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking any drug during pregnancy or lactation.

    This drug should not be given to women who are pregnant. It may affect the fetus, especially in the second and third trimester. Additionally, this drug may pass into breastmilk, therefore do not breastfeed while taking this drug.

    Know the side effects

    What are the side effects of mefenamic acid?

    Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

    • Stomach pain
    • Nausea, vomiting
    • Heartburn
    • Constipation, diarrhea
    • Rash
    • Dizziness
    • Tinnitus

    Seek medical attention if you experience any of the following:

    However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.

    Know the interactions

    What drugs may interact with mefenamic acid?

    This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. 

    To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. 

    Drugs with known interactions:

    • ACE inhibitors (e.g. captopril, enalapril)
    • Methotrexate
    • Magnesium hydroxide
    • Lithium
    • Blood thinners (e.g. aspirin, warfarin, coumarin)
    • Diuretics

    If you experience an adverse drug interaction, inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

    Does food or alcohol interact with mefenamic acid?

    This drug may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Do not consume alcohol while taking this drug. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

    What health conditions may interact with mefenamic acid?

    This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

    • Anemia
    • Asthma
    • Bleeding problems
    • Blood clots
    • Edema (fluid retention or body swelling)
    • Heart disease (e.g., congestive heart failure)
    • Hypertension (high blood pressure)
    • Kidney disease
    • Liver disease (e.g. hepatitis)
    • Stomach or intestinal ulcers or bleeding
    • Stroke
    • Aspirin-sensitive asthma
    • Kidney disease, advanced
    • Heart surgery (e.g., coronary artery bypass graft [CABG] surgery)

    Understand the dosage

    The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

    What is the dose for an adult?

    Pain relief

    Take 500 mg three times a day. Take it for the shortest duration possible.

    What is the dose for a child?

    Pain relief

    Children aged 14 years and older: Give 500 mg three times a day.

    Do not give it to children under 14 years.

    How is mefenamic acid available?

    Mefenamic acid is available in the following dosage forms and strengths:

    • Capsule: 250 mg, 500 mg
    • Tablet: 250 mg, 500 mg
    • Oral suspension: 50 mg/5mL

    What should I do in case of an emergency or overdose?

    In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

    What should I do if I miss a dose?

    If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Written by

    Stephanie Nera, RPh, PharmD


    Updated Jul 21, 2022

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