SIDE EFFECTS: See also Warning section. Upset stomach, nausea, heartburn, dizziness, drowsiness, diarrhea, and headache may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. This medication may raise your blood pressure. Check your blood pressure regularly and tell your doctor if the results are high. Tell your doctor right away if any of these unlikely but serious side effects occur: fainting, persistent/severe headache, hearing changes (e.g., ringing in the ears), fast/pounding heartbeat, mental/mood changes, stomach pain, difficult/painful swallowing, vision changes, symptoms of heart failure (such as swelling ankles/feet, unusual tiredness, unusual/sudden weight gain). Stop taking mefenamic acid and tell your doctor right away if any of these rare but very serious side effects occur: easy bruising/bleeding, signs of infection (e.g., fever, persistent sore throat), unexplained stiff neck, change in the amount/color of urine. This drug may rarely cause serious, possibly fatal liver disease. If you notice any of the following rare but very serious side effects, stop taking mefenamic acid and consult your doctor or pharmacist right away: persistent nausea/vomiting, severe stomach/abdominal pain, weakness, dark urine, yellowing eyes/skin. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking mefenamic acid, tell your doctor or pharmacist if you are allergic to it; or to aspirin or other NSAIDs (e.g., ibuprofen, naproxen, celecoxib); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: aspirin-sensitive asthma (a history of worsening breathing with runny/stuffy nose after taking aspirin or other NSAIDs, severe kidney disease, recent heart bypass surgery (CABG), active bleeding/sores in stomach/intestines (ulcer, gastrointestinal bleeding). Before using this medication, tell your doctor or pharmacist your medical history, especially of: asthma, bleeding/clotting problems, blood disorders (e.g., anemia), high blood pressure, diabetes, heart disease (e.g., history of heart attack), liver disease, growths in the nose (nasal polyps), obesity, tobacco use, history of stomach/intestine/esophagus problems (e.g., bleeding, ulcers, recurring heartburn), stroke, swelling of the ankles/feet/hands. Kidney problems can sometimes occur with the use of NSAID medications, including mefenamic acid. Problems are more likely to occur if you are dehydrated, have heart failure or kidney disease, are an older adult, or if you take certain medications (see also Drug Interactions section). Drink plenty of fluids as directed by your doctor to prevent dehydration and tell your doctor right away if you have a change in the amount of urine. Before having surgery, tell your doctor or dentist that you are using this medication. This drug may make you dizzy or drowsy. Alcohol or marijuana can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana. This medicine may cause stomach bleeding. Daily use of alcohol and tobacco, especially when combined with this medicine, may increase your risk for stomach bleeding. Limit alcohol and stop smoking. Consult your doctor or pharmacist for more information. This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness. Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, caution is advised when using this drug in the elderly because they may be more sensitive to its side effects, especially stomach bleeding and kidney problems. Before using this medication, women of childbearing age should talk with their doctor(s) about the benefits and risks (such as miscarriage, trouble getting pregnant). Tell your doctor if you are pregnant or if you plan to become pregnant. During pregnancy, this medication should be used only when clearly needed. It is not recommended for use during the first and last trimesters of pregnancy due to possible harm to the unborn baby and interference with normal labor/delivery. This drug passes into breast milk and may have undesirable effects on a nursing infant. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Some products that may interact with this drug include: aliskiren, ACE inhibitors (such as captopril, lisinopril), angiotensin II receptor blockers (such as valsartan, losartan), cidofovir, corticosteroids (e.g., prednisone), fluconazole, ketorolac, lithium, methotrexate, "water pills" (diuretics such as furosemide). This medication may increase the risk of bleeding when taken with other drugs that also may cause bleeding. Examples include anti-platelet drugs such as clopidogrel, "blood thinners" such as dabigatran/enoxaparin/warfarin, among others. Check all prescription and nonprescription medicine labels carefully since many medications contain pain relievers/fever reducers (aspirin, NSAIDs such as celecoxib or ibuprofen). These drugs are similar to mefenamic acid and may increase your risk of side effects if taken together. However, if your doctor has directed you to take low-dose aspirin to prevent heart attack or stroke (usually at dosages of 81-325 milligrams a day), you should continue taking the aspirin unless your doctor instructs you otherwise. Ask your doctor or pharmacist for more details. This medication may interfere with certain laboratory tests (e.g., urine bile test), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe stomach pain, vomit that looks like coffee grounds, extreme drowsiness, slow/shallow breathing, seizures.