Mefenamic acid (By mouth)
Mefenamic Acid (mef-e-NAM-ik AS-id)
Treats pain, including menstrual pain. This medicine is an NSAID.
When This Medicine Should Not Be Used
How to Use This Medicine
- Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
- It is best to take this medicine with food or milk so it does not upset your stomach.
- Use this medicine for the shortest time possible and in the smallest dose possible. This will help lower the risk of side effects.
- This medicine should come with a Medication Guide. Ask your pharmacist for a copy if you do not have one.
If a dose is missed:
- Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
How to Store and Dispose of This Medicine
- Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
- Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
- Keep all medicine out of the reach of children. Never share your medicine with anyone.
Drugs and Foods to Avoid
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.
- Make sure your doctor knows if you are also using aspirin, a blood thinner (such as warfarin, Coumadin®), or a steroid medicine (such as cortisone, dexamethasone, hydrocortisone, methylprednisolone, prednisolone, prednisone, or Orapred®). Tell your doctor if you are using methotrexate (Trexall®), or a diuretic or "water pill" (such as furosemide, hydrochlorothiazide [HCTZ], torsemide, Demadex®, or Lasix®).
- Make sure your doctor knows if you are using fluconazole (Diflucan®), lithium (Eskalith®), lovastatin (Mevacor®), trimethoprim, or an antacid (such as milk of magnesia, Maalox®, or Mylanta®). Tell your doctor if you are using a blood pressure medicine such as captopril, enalapril, lisinopril, Accupril®, Lotensin®, Lotrel®, Mavik®, Monopril®, Prinivil®, Zestoretic®, or Zestril®.
- Do not use any other NSAID medicine unless your doctor says it is okay. Some other NSAIDs are aspirin, diclofenac, ibuprofen, naproxen, Advil®, Aleve®, Celebrex®, Ecotrin®, Motrin®, or Voltaren®.
Warnings While Using This Medicine
- Make sure your doctor knows if you are pregnant or breastfeeding. Do not use this medicine during the later part of a pregnancy unless your doctor tells you to.
- Make sure your doctor knows if you have a history of ulcers or other stomach problems. Tell your doctor if you have kidney disease, liver disease, anemia, asthma, bleeding problems, high blood pressure, congestive heart failure (CHF), or heart or circulation problems.
- This medicine may raise your risk of having a heart attack or stroke. This is more likely in people who already have heart disease. People who use this medicine for a long time might also have a higher risk.
- This medicine may cause bleeding in your stomach or intestines. This is more likely if you have had a stomach ulcer in the past, if you smoke or drink alcohol regularly, if you are over 60 years old, if you are in poor health, or if you are using certain other medicines (a steroid medicine or a blood thinner).
- You should not use mefenamic acid for more than 7 days unless your doctor tells you to.
- This medicine may cause a serious type of allergic reaction called anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Call your doctor right away if you have a rash; itching; hoarseness; trouble breathing; trouble swallowing; or any swelling of your hands, face, or mouth while you are using this medicine.
- Serious skin reactions can occur with this medicine. Check with your doctor right away if you have blistering, peeling, or loosening of the skin; red skin lesions; severe acne or skin rash; sores or ulcers on the skin; or fever or chills while you are using this medicine.
- Liver problems may occur while you are using this medicine. Stop using this medicine and check with your doctor right away if you are having more than one of these symptoms: abdominal pain or tenderness; clay-colored stools; dark urine; decreased appetite; fever; headache; itching; loss of appetite; nausea and vomiting; skin rash; swelling of the feet or lower legs; unusual tiredness or weakness; or yellow eyes or skin.
- Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
- This medicine may make your skin more sensitive to sunlight. Wear sunscreen. Do not use sunlamps or tanning beds.
- Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
Possible Side Effects While Using This Medicine
Call your doctor right away if you notice any of these side effects:
- Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
- Blistering, peeling, or red skin rash.
- Bloody or black, tarry stools.
- Change in how much or how often you urinate.
- Chest pain, shortness of breath, or coughing up blood.
- Dark-colored urine or pale stools.
- Flu-like symptoms.
- Numbness or weakness in your arm or leg, or on one side of your body.
- Pain in your lower leg (calf).
- Problems with vision, speech, or walking.
- Shortness of breath, cold sweat, and bluish-colored skin.
- Skin rash or blisters with fever.
- Sudden and severe stomach pain, nausea, vomiting, fever, and lightheadedness.
- Sudden or severe headache.
- Swelling in your hands, ankles, or feet.
- Unusual bleeding, bruising, or weakness.
- Vomiting blood or something that looks like coffee grounds.
- Yellowing of your skin or the whites of your eyes.
If you notice these less serious side effects, talk with your doctor:
- Constipation or diarrhea.
- Headache, dizziness, or weakness.
- Indigestion or gas.
- Mild heartburn, nausea, vomiting, or stomach pain or upset.
- Mild skin rash and itching skin.
- Problems with your vision.
- Rapid weight gain, or unexpected weight loss.
- Ringing in your ears.
If you notice other side effects that you think are caused by this medicine, tell your doctor
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088
- Last reviewed on 4/8/2016
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