Before taking guanfacine,
tell your doctor and pharmacist if you are allergic to guanfacine, any other medications, or any of the ingredients in guanfacine tablets or extended-release tablets. Ask your pharmacist for a list of the ingredients.
you should know that guanfacine is the active ingredient in guanfacine tablets and guanfacine extended-release tablets. Do not take both of these products at the same time.
tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Be sure to mention any of the following: antidepressants; antihistamines; barbiturates such as phenobarbital (Luminal); carbamazepine (Carbatrol, Epitol, Equetro, Tegretol); clarithromycin (Biaxin, in PrevPac); indinavir (Crixivan); itraconazole (Onmel, Sporanox); ketoconazole (Nizoral); medications for anxiety, high blood pressure, mental illness, nausea, or seizures; nefazodone; nelfinavir (Viracept); phenytoin (Dilantin, Phenytek); pioglitazone (Actos, in Actoplus Met, in Duetact, in Oseni); rifabutin (Mycobutin); rifampin (Rifadin, in Rifamate, in Rifater, Rimactane); ritonavir (Norvir, in Kaletra); sedatives; sleeping pills; tranquilizers; and valproic acid (Depakene). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
tell your doctor what herbal products you are taking, especially St. John's wort.
tell your doctor if you have ever fainted, or if you have recently had a heart attack; and if you have or have ever had a stroke; low blood pressure; a slow heart rate; bipolar disorder (manic depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods); or heart, kidney or liver disease.
tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking guanfacine, call your doctor.
if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking guanfacine.
you should know that guanfacine may make you drowsy or dizzy. Do not drive a car or operate machinery until you know how this medication affects you.
ask your doctor about the safe use of alcoholic beverages while you are taking guanfacine. Alcohol can make the side effects from guanfacine worse.
you should know that guanfacine may cause dizziness, lightheadedness, and fainting when you get up too quickly from a lying position. This is more common when you first start taking guanfacine. To avoid this problem, get out of bed slowly, resting your feet on the floor for a few minutes before standing up.
you should know that you may faint if you become dehydrated or overheated during your treatment with guanfacine. Be sure to drink plenty of liquids and stay cool while you are taking this medication.
you should know that guanfacine should be used as part of a total treatment program for ADHD, which may include counseling and special education. Make sure to follow all of your doctor's and/or therapist's instructions.