SIDE EFFECTS: See also Warning section. Upset stomach, heartburn, headache, tiredness, drowsiness, or dizziness 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. Tell your doctor right away if any of these unlikely but serious side effects occur: stomach pain, vision changes, hearing changes (e.g., ringing in the ears), mental/mood changes (e.g., confusion, hallucinations), fast/pounding heartbeat, persistent/severe headache, fainting, difficult/painful swallowing, symptoms of heart failure (such as swelling ankles/feet, unusual tiredness, unusual/sudden weight gain). Tell your doctor right away if any of these rare but very serious side effects occur: signs of kidney problems (such as change in the amount of urine), easy bruising/bleeding, signs of infection (e.g., fever, persistent sore throat), unexplained stiff neck. 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 diflunisal and tell your doctor right away: yellowing eyes/skin, dark urine, unusual/extreme tiredness, severe stomach/abdominal pain, persistent nausea/vomiting. A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: 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: See also Warning section. Before taking diflunisal, tell your doctor or pharmacist if you are allergic to it; or to aspirin or other salicylates (e.g., choline salicylate), 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. Before using this medication, tell your doctor or pharmacist your medical history, especially of: asthma (including a history of worsening breathing after taking aspirin or other NSAIDs), liver disease, poorly controlled diabetes, stomach/intestine/esophagus problems (e.g., bleeding, ulcers), heart disease (e.g., history of heart attack), stroke, high blood pressure, swelling (edema, fluid retention), blood disorders (e.g., anemia), bleeding or clotting problems, growths in the nose (nasal polyps). Kidney problems can sometimes occur with the use of NSAID medications, including diflunisal. 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. Talk to your doctor if you are using marijuana. This medicine may cause stomach bleeding. Daily use of alcohol and tobacco may increase your risk for stomach bleeding, especially when combined with this medicine. Limit alcohol and stop smoking. Consult your doctor or pharmacist for more information. The elderly may be more sensitive to the side effects of this drug, especially stomach/intestinal bleeding and kidney problems. This medication is not recommended for use in children under 12 years of age. In addition, since diflunisal is related to aspirin, children and teenagers should not take diflunisal if they have chickenpox, influenza, or any undiagnosed illness without first consulting a doctor about Reye's syndrome, a rare but serious illness. 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. Therefore, breast-feeding while using this drug is not recommended. 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 losartan, valsartan), antacids (regular use), cidofovir, corticosteroids (e.g., prednisone), digoxin, live influenza vaccine, lithium, methotrexate, pemetrexed, probenecid, "water pills" (diuretics such as furosemide, hydrochlorothiazide, triamterene). 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 contain pain relievers/fever reducers (NSAIDs such as aspirin, ibuprofen, indomethacin, ketorolac or naproxen) which if taken together with diflunisal may increase your risk for side effects. Low-dose aspirin, as prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention (usually at dosages of 81-325 milligrams per day), should be continued. Consult your doctor or pharmacist for more details. This medication can affect the results of certain lab tests. Make sure laboratory personnel and 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, fast breathing, confusion, loss of consciousness.