What side effects can this medication cause?
If you experience any of the following serious side effects, stop taking guanfacine and seek emergency medical attention:
an allergic reaction (difficulty breathing, closing of your throat, swelling of your lips, tongue, or face, or hives)
a very slow heart rate (fewer than 60 beats per minute)
unusually high or low blood pressure (fainting, a severe headache, flushing of your face)
Other, less serious side effects may be more likely to occur. Continue to take guanfacine and talk to your doctor if you experience any of the following:
unusual fatigue, dizziness, or tiredness
headache
constipation, nausea, vomiting, or diarrhea
insomnia
dry mouth (sucking on ice chips or sugarless hard candy may relieve this side effect)
Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.
Why is this medication prescribed?
Dosage and using this medicine
What special precautions should I follow?
What should I do if I forget a dose?