See also How to Use section.Stomach/abdominal cramping may occur, usually within the first several hours after taking this medication. Nausea, loss of appetite, heartburn, and headache may also occur. If any of these effects persist or worsen, tell 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 immediately if any of these unlikely but serious side effects occur: eye redness/pain, hair loss, numbness/tingling of arms/legs.This medication may cause mouth/lip/throat sores (stomatitis). Tell your doctor if you notice a metallic taste in your mouth. This could be the first sign of stomatitis. Rinsing your mouth with a mild salt solution may provide some relief. Discuss with your doctor.Tell your doctor immediately if any of these rare but very serious side effects occur: signs of low blood count (e.g., fast/pounding heartbeat, pale skin, unusual tiredness), easy bleeding/bruising, black/bloody stools, persistent cough, mucus/pus/blood in watery diarrhea, difficult/painful breathing, dizziness, signs of infection (e.g., fever, persistent sore throat), severe stomach/abdominal pain, unusual tiredness, change in the amount/color of urine, vomit that looks like coffee grounds, yellowing eyes/skin.A very serious allergic reaction to this drug is uncommon. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: itching/swelling (especially of the face/tongue/throat), rash, severe dizziness, trouble breathing.Skin rash is common with this medication and can be serious. Itching is often the first sign of a severe allergic reaction. Therefore, seek immediate medical attention if you develop any rash or itching.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.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.