Nausea, vomiting, diarrhea, loss of appetite, or headache may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.
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: mental/mood changes (such as depression, hallucinations), signs of kidney problems (such as change in the amount of urine, crystals in the urine, painful urination), lump/growth/swelling in the front of the neck (goiter), signs of low blood sugar (such as shaking, dizziness, blurred vision, unusual hunger).
This medication may rarely cause a severe intestinal condition due to a bacteria called C. difficile. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop: diarrhea that doesn't stop, abdominal or stomach pain/cramping, blood/mucus in your stool.
If you have these symptoms, do not use anti-diarrhea or opioid products because they may make symptoms worse.
Use of this medication for prolonged or repeated periods may result in oral thrush or a new vaginal yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.
Get medical help right away if you have any very serious side effects, including: headache that is severe or doesn't go away, confusion, neck stiffness, seizures.
This medication may rarely cause serious (possibly fatal) allergic reactions and other side effects such as a severe peeling skin rash (such as Stevens-Johnson syndrome), blood disorders (such as agranulocytosis, aplastic anemia), liver damage, or lung injury. Get medical help right away if you notice any of the following: cough that doesn't go away, nausea/vomiting that doesn't stop, skin rash/blisters, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing, signs of a new infection (such as sore throat that doesn't go away, fever), pale skin, easy bleeding/bruising, yellowing eyes/skin, unusual tiredness, dark urine, stomach/abdominal pain, joint pain.
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 MedWatch: The FDA Safety Information and Adverse Event Reporting Program.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.