Stomach upset, nausea, vomiting, loss of appetite, headache, dizziness, or unusual tiredness may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. This medication may cause your skin and urine to turn orange-yellow. This effect is harmless and will disappear when the medication is stopped. Rarely, delayed-release tablets of sulfasalazine may appear whole or only partly dissolved in your stool. If this occurs, tell your doctor right away so your treatment can be changed. Remember that this medication has been prescribed because your doctor 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 you have any serious side effects, including: hearing changes (such as ringing in the ears), mental/mood changes, signs of kidney problems (such as change in the amount of urine, painful urination, blood in the urine), new lump/growth in the neck (goiter), numbness/tingling of the hands/feet, signs of low blood sugar (such as hunger, cold sweat, blurred vision, weakness, fast heartbeat). This medication may rarely cause very serious allergic reactions (such as Stevens-Johnson syndrome), blood disorders (such as agranulocytosis, aplastic anemia), liver damage, nerve/muscle problems and infections. Get medical help right away if you have any very serious side effects, including: headache that is severe or doesn't go away, skin rash/blisters/peeling, mouth sores, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing, chest pain, signs of infection (such as sore throat that doesn't go away, fever, chills, cough), swollen lymph nodes, easy bruising/bleeding, severe tiredness, muscle pain/weakness (especially with fever and unusual tiredness), pale or blue skin/lips/nails, new/worsening joint pain, confusion, unexplained neck stiffness, seizures, signs of liver problems (such as nausea/vomiting that doesn't stop, severe stomach/abdominal pain, yellowing eyes/skin, dark urine). 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.

Some products that may interact with this drug include: digoxin, folic acid, methenamine, PABA taken by mouth. Sulfasalazine is very similar to mesalamine. Do not use mesalamine medications taken by mouth while using sulfasalazine. This medication may interfere with certain lab tests (such as urine normetanephrine levels, liver function tests), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.