Why is this medication prescribed?
Mefenamic acid is used to relieve mild to moderate pain, including menstrual pain (pain that happens before or during a menstrual period). Mefenamic acid is in a class of medications called NSAIDs. It works by stopping the body’s production of a substance that causes pain, fever, and inflammation.
How should this medicine be used?
Mefenamic acid comes as a capsule to take by mouth. It is usually taken with food every 6 hours as needed for up to 1 week. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take mefenamic acid exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Other uses for this medicine
This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
What special precautions should I follow?
Before taking mefenamic acid,
- tell your doctor and pharmacist if you are allergic to mefenamic acid, aspirin or other NSAIDs such as ibuprofen (Advil, Motrin) and naproxen (Aleve, Naprosyn), any other medications, or any of the inactive ingredients in mefenamic acid capsules. Ask your pharmacist for a list of the inactive ingredients.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention the medications listed in the IMPORTANT WARNING section and any of the following: antacids; angiotensin-converting enzyme (ACE) inhibitors such as benazepril (Lotensin, in Lotrel), captopril, enalapril (Vasotec, in Vaseretic), fosinopril, lisinopril (in Zestoretic), moexipril (Univasc), perindopril (Aceon, in Prestalia), quinapril (Accupril, in Quinaretic), ramipril (Altace), and trandolapril (Mavik, in Tarka); amiodarone (Cordarone, Nexterone, Pacerone); angiotensin receptor blockers such as azilsartan (Edarbi, in Edarbyclor), candesartan (Atacand, in Atacand HCT), eprosartan (Teveten), irbesartan (Avapro, in Avalide), losartan (Cozaar, in Hyzaar), olmesartan (Benicar, in Azor, in Benicar HCT, in Tribenzor), telmisartan (Micardis, in Micardis HCT, in Twynsta); beta blockers such as atenolol (Tenormin, in Tenoretic), labetalol (Trandate), metoprolol (Lopressor, Toprol XL, in Dutoprol), nadolol (Corgard, in Corzide), and propranolol (Hemangeol, Inderal, InnoPran); atazanavir (Reyataz, in Evotax); clopidogrel (Plavix); diuretics (‘water pills’), efavirenz (Sustiva, in Atripla); fluconazole (Diflucan); fluvastatin (Lescol); metronidazole (Flagyl); lithium (Lithobid); lovastatin (Altoprev, Mevacor); methotrexate (Otrexup, Rasuvo, Trexall); ritonavir (Norvir, in Kaletra); sulfamethoxazole (in Bactrim, in Septra); sulfinpyrazone (no longer available in U.S.; Anturane); trimethoprim (Primsol, in Bactrim, in Septra); and zafirlukast (Accolate). Your doctor may need to change the doses of your medications or monitor you more carefully for side effects.
- tell your doctor if you have or have ever had any of the conditions mentioned in the IMPORTANT WARNING section or asthma, especially if you also have frequent stuffed or runny nose or nasal polyps (swelling of the inside of the nose); heart failure; swelling of the hands, feet, ankles, or lower legs (fluid retention); or liver or kidney disease.
- tell your doctor if you are pregnant, especially if you are in the last few months of your pregnancy, you plan to become pregnant, or you are breastfeeding. If you become pregnant while taking mefenamic acid, call your doctor.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking mefenamic acid.
What special dietary instructions should I follow?
Unless your doctor tells you otherwise, continue your normal diet.
What should I do if I forget a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What side effects can this medication cause?
Mefenamic acid may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- gas or bloating
- ringing in the ears
Some side effects can be serious. If you experience any of the following symptoms or those mentioned in the IMPORTANT WARNING section, call your doctor immediately. Do not take any more mefenamic acid until you speak to your doctor.
- blurred vision
- unexplained weight gain
- shortness of breath or difficulty breathing
- swelling of feet, ankles, or lower legs
- swelling of the eyes, face, lips, tongue, throat, hands, or arms
- difficulty breathing or swallowing
- pale skin
- fast heartbeat
- excessive tiredness
- unusual bleeding or bruising
- lack of energy
- loss of appetite
- pain in the upper right part of the stomach
- flu-like symptoms
- yellowing of the skin or eyes
- cloudy, discolored, or bloody urine
- back pain
- difficult or painful urination
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).
What should I know about storage and disposal of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).
Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.
It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org
In case of emergency/overdose
In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.
Symptoms of overdose may include the following:
- extreme tiredness
- stomach pain
- vomit that is bloody or looks like coffee grounds
- black, tarry, or bloody stools
- slowed breathing
- coma (loss of consciousness for a period of time)
What other information should I know?
Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking mefenamic acid.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.