Nervousness, trouble sleeping, loss of appetite, weight loss, dizziness, nausea, vomiting, or headache may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
An empty tablet shell may appear in your stool. This effect is harmless because your body has already absorbed the medication.
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 medication may raise your blood pressure. Check your blood pressure regularly and tell your doctor if the results are high.
Tell your doctor right away if you have any serious side effects, including: signs of blood flow problems in the fingers or toes (such as coldness, numbness, pain, or skin color changes), unusual wounds on the fingers or toes, fast/pounding/irregular heartbeat, mental/mood/behavior changes (such as agitation, aggression, mood swings, abnormal thoughts, thoughts of suicide), uncontrolled muscle movements (such as twitching, shaking), sudden outbursts of words/sounds that are hard to control, vision changes (such as blurred vision).
Get medical help right away if you have any very serious side effects, including: fainting, seizure, symptoms of a heart attack (such as chest/jaw/left arm pain, shortness of breath, unusual sweating), symptoms of a stroke (such as weakness on one side of the body, slurred speech, sudden vision changes, confusion).
Rarely, males (including young boys and teens) may have a painful or prolonged erection lasting 4 or more hours while using this medication. Caregivers/parents should also be watchful for this serious side effect in boys. If a painful or prolonged erection occurs, stop using this drug and get medical help right away, or permanent problems could occur. Ask your doctor or pharmacist for more details.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: 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.