Guanfacine ER

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Mar 11, 2024

Warnings

Guanfacine ER (Intuniv) Risks, Warnings, and Complications

Guanfacine ER may cause or worsen health problems in some people. Discuss other medications for attention deficit hyperactivity disorder with your doctor or pharmacist if you are at a higher risk of adverse effects from this drug.

LOW BLOOD PRESSURE, SLOW HEART RATE, AND FAINTING: Taking guanfacine ER can lead to a decrease in blood pressure and heart rate. There are also reports of orthostatic hypotension (postural hypotension or low blood pressure when going from a lying or sitting position to a standing position) and fainting. The risk of these side effects is more at higher doses. Your doctor will monitor your blood pressure and heart rate periodically while you are on this medicine. Avoid getting overheated or dehydrated, as this can increase the risk of fainting.
SEDATION AND SLEEPINESS: Sleepiness and sedation are common side effects of guanfacine ER. Taking other CNS depressants such as sedatives, hypnotics, tranquilizers, opioid pain medications, and muscle relaxants can make these adverse effects worse. Give your doctor a complete list of your medications before starting treatment. Do not drive or operate machinery until you know how guanfacine ER affects you.
HEART ABNORMALITIES: Guanfacine ER can worsen certain heart conduction abnormalities such as AV block or sinus node dysfunction. These adverse effects can be made worse by certain sympatholytic medications. Tell your doctor about all your known medical problems. Your doctor will increase your dose slowly or choose a different medication if you have known cardiac conduction abnormalities.
REBOUND HYPERTENSION: Suddenly stopping guanfacine ER can lead to an increase in blood pressure, especially if you are on high-dose guanfacine and stimulant medications. Children are at an especially high risk of this side effect. To lower the risk of this happening, your doctor will tell you how to reduce the dose gradually every 3-7 days.

Precautions Before Starting Guanfacine ER (Intuniv)

Tell your doctor if you have had allergic reactions to guanfacine hydrochloride, any of the active or inactive ingredients in guanfacine ER tablets, other medications prescribed for ADHD, or any other drugs. Your pharmacy can give you a list of ingredients.

To avoid possible interactions between guanfacine ER and your other medicines, give your doctor and pharmacist a full list of your medications, including prescription medications, over-the-counter medicines, vitamins, dietary supplements, and herbal remedies, especially St. John’s Wort.

Give your healthcare provider a complete medical history. Guanfacine ER may not be safe for people with certain health conditions such as slow heart rate, low blood pressure, fainting, heart attack, stroke, a mental illness such as bipolar disorder, heart disease, renal impairment, or renal failure (kidney disease), or hepatic impairment (liver disease).

Tell your doctor if you are pregnant, could be pregnant, plan to get pregnant, or are breast-feeding.

Precautions During Use of Guanfacine ER (Intuniv)

Keep all your medical and lab appointments while on guanfacine ER. Your doctor may adjust your dose based on your response to the medicine.

Do not take guanfacine tablets (prescribed for high blood pressure) at the same time as guanfacine ER for ADHD.

Guanfacine ER can cause lightheadedness, dizziness, and drowsiness. Be careful while driving or operating machinery until you know how the medicine affects you. Get up slowly from a lying or sitting position to prevent lightheadedness.

Avoid becoming overheated or dehydrated while on this medication. Stay cool and drink plenty of fluids.

Do not take guanfacine ER with a high-fat meal. This can lead to increased absorption of the medicine and more severe side effects.

Talk to your doctor about drinking alcohol while on guanfacine ER. Alcohol can worsen some of the side effects of this medicine.

Elderly patients above 65 years of age should discuss the risks versus benefits of taking guanfacine ER with their doctor. There may be other safer medications available.

Tell your doctor if you become pregnant while on guanfacine ER. This medication did not cause fetal harm in animal studies, but no placebo-controlled study or well-controlled clinical trials have been done in humans (pregnant women).

Tell all your healthcare providers you are on guanfacine ER before any surgery, including dental surgery.

Guanfacine ER is used to treat ADHD as part of a comprehensive treatment plan, which includes behavior therapy, counseling, training, and medications. Follow your doctor’s recommendations for treating ADHD to get the maximum improvement in your symptoms.

Guanfacine ER (Intuniv) Drug Interactions

Taking certain other medicines with guanfacine ER can affect how the medications work. Possible drug interactions can increase the risk of severe adverse effects. The following medications can have interactions with guanfacine ER:

Antihistamines
Antidepressants such as nefazodone
Anti-seizure medications such as carbamazepine (Tegretol, Carbatrol, Epitol, Equetro), phenytoin (Dilantin, Phenytek), valproic acid (Depakene), and phenobarbital (Luminal)
Antibiotics such as clarithromycin (Biaxin, in PrevPac), rifabutin (Mycobutin), and rifampin (Rimactane, Rifadin, in Rifater, in Rifamate)
Antiviral medications used to treat HIV, such as indinavir (Crixivan), nelfinavir (Viracept), and ritonavir (Norvir, in Kaletra)
Antifungal agents such as itraconazole (Onmel, Sporanox) and ketoconazole (Nizoral)
Medications used to treat high blood pressure, anxiety, mental illnesses, seizures, and nausea
Diabetes medications such as pioglitazone (Actos, in Duetact, in Actoplus Met, in Oseni)
Sedatives, hypnotics, tranquilizers, sleeping pills

The above list may not include all the potential interactions of guanfacine ER. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, nonprescription drugs, nutritional supplements, and herbal remedies. Also, tell your healthcare professional if you smoke, drink alcohol, or use illegal drugs because some of these substances can cause serious health complications when used with prescription medications.

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