Dizziness, lightheadedness, drowsiness, tiredness, constipation, diarrhea, stomach upset/gas, nausea, trouble sleeping or unusual dreams may occur as your body adjusts to the medication. 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 drug may reduce blood flow to your hands and feet, causing them to feel cold. Smoking may worsen this effect. Avoid tobacco use and dress warmly. Tell your doctor immediately if any of these unlikely but serious side effects occur: bluish discoloration of the fingers/toes/nails, severe tiredness, mental/mood changes (e.g., depression, confusion, memory problems), numbness/tingling, decreased sexual ability, trouble breathing, swelling of the feet/ankles, vision changes, unexplained/sudden weight gain. Seek immediate medical attention if any of these unlikely but very serious side effects occur: chest pain, persistent dizziness/fainting, slow/fast/irregular heartbeat, jaw/left arm pain, black stools, rectal bleeding, severe stomach/abdominal pain. Tell your doctor immediately if any of these rare but very serious side effects occur: easy bleeding/bruising, persistent joint/muscle pain, painful erections. Tell your doctor immediately if you develop symptoms of liver disease, including persistent nausea, stomach/abdominal pain, dark urine, yellowing eyes/skin. 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. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.