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What is guanfacine?

Guanfacine (Intuniv XR®) belongs to a group of medications called “alpha2-agonists”. It is approved by Health Canada to treat attention deficit/hyperactivity disorder (AD/HD).

What is guanfacine used for?

Guanfacine is mainly used to treat AD/HD.

However, when the potential benefits (e.g., reducing your symptoms) of using guanfacine outweigh the potential risks (e.g., the side effects), doctors may prescribe it “off-label” to treat the other following conditions:

• Anxiety disorders
• Disruptive behaviour disorders (including aggression)
• Tic disorders (e.g. shrugging, blinking, head turning, muscle twitches, and throat clearing)

Your doctor may be prescribing this medication to you for another reason. If you are unclear why guanfacine is being prescribed, please ask your doctor.

How does guanfacine work?

Guanfacine works by affecting the activity of the brain chemical (neurotransmitter) called norepinephrine. Norepinephrine normally influences blood pressure, heart rate and anxiety in the body, but it also affects attention and arousal. This medication stabilizes certain areas of the brain, making them “less excited”. This in turn improves symptoms of AD/HD and tic disorders.

How well does guanfacine work in children and adolescents?

Guanfacine does not cure AD/HD. This medication aims to improve functioning by moderately reducing AD/HD symptoms such as hyperactivity and impulsive behaviour. It can also help you tolerate frustration better. Guanfacine is an important treatment option for patients who have undesirable side effects from, or do not respond to stimulant treatment.

Guanfacine may be particularly helpful for patients with impulsive behaviour or hyperactivity problems, and who may also have aggression, hostility or tic disorders. Guanfacine can be taken alone or combined with stimulants to treat these conditions. Guanfacine should be used as a part of a total treatment program for AD/HD that may include counselling or other therapies (for example: rewarding good behaviour, teaching problem-solving techniques) to increase the chance for benefit.

How should guanfacine be taken?

Guanfacine is available as extended-release tablets that are taken by mouth. Do not crush, chew or break guanfacine extended-release tablets, as this may increase the rate of medication release and lead to side effects like dizziness or sedation. Do not take guanfacine with a high-fat meal, as this may increase the amount of medication absorbed. Your doctor will determine how much you should take, according to your body weight and your response to this medication.

When starting treatment with guanfacine, your doctor may start with a lower dose and then slowly increase the dose over a few weeks, until the ideal dose is reached or side effects occur. Guanfacine is usually taken once per day and should be taken regularly on a daily basis at the same time everyday to be effective. Treatment with guanfacine should not be stopped suddenly, since this could lead to an undesirable rapid increase in blood pressure.

When will guanfacine start working?

Guanfacine usually needs to be taken for two weeks before you see an improvement in your symptoms. It may take several weeks to see the full benefits of the medication. Effects such as drowsiness and sedation may appear sooner (even after the first dose). Unless directed by your doctor, do not increase, decrease, or stop taking the medication if there are no improvements in the first few weeks. This delay in response is normal.

Medications like guanfacine do not work for everyone. If you are not feeling better within several weeks, your doctor may recommend switching you to a different medication.

How long do I have to take guanfacine?

This depends on the symptoms you have, how frequently they occur, and how long you have had them. Different people take guanfacine for different lengths of time. Whether or not you need medication should be reevaluated from time to time. Some people only require it during particular times of their life such as when they are in school, whereas some people continue to benefit from medication for many years.

It may be dangerous to suddenly stop taking guanfacine after you have been taking it on a regular basis. If you and your doctor decide to stop using guanfacine, your doctor will explain how to safely lower the dose gradually to prevent a rapid increase in blood pressure and other undesirable effects as your body adjusts to being without it. Do not stop taking this medication suddenly without first discussing it with your doctor.

Is guanfacine addictive?

No, guanfacine is not addictive and you will not have “cravings” for it like some people do with nicotine or street drugs. In general, people with AD/HD may be at an increased risk to abuse substances over the long run. By effectively treating AD/HD, patients may be less likely to abuse substances than those who do not take medications to help manage AD/HD.

What are the side effects of guanfacine and what should I do if I get them?

As with most medications, side effects may occur when taking guanfacine. These effects are usually more common when starting a medication or after a dose increase. Most side effects are mild and almost always decrease with time. It is also possible to experience a side effect that you feel is serious or long-lasting. If this occurs, speak to your doctor about ways to manage them. On the next page are some of the more common side effects of taking this medicine. In brackets are suggested ways to lessen these effects.

Common side effects

If any of these side effects bother you or are a change from your usual pattern, please discuss them with your doctor, nurse or pharmacist:

• Constipation (try drinking more fluids, exercising, or increasing the amount of fiber in your diet)
• Dizziness, lightheadedness or low blood pressure (try getting up slowly from a sitting or lying down position. If it becomes severe (for example: falling or fainting), seek medical help immediately)
• Drowsiness or fatigue (try taking the dose at bedtime. Do not drive or operate machinery until you know how this medication affects you. If guanfacine makes you drowsy during the daytime, talk with your doctor.)
• Dry eyes (try using artificial tears eye drops)
• Dry mouth (try chewing sugarless gum or sucking hard sugar-free candies, ice chips, or popsicles)
• Headache (try using a pain reliever like acetaminophen (Tylenol®). If your headache comes on suddenly and is extremely intense, seek emergency help immediately)
• Stomach upset, nausea, vomiting (try taking the medication with a low-fat snack or meal)

Potentially serious but uncommon side effects (e.g., those that occur in less than 5% of patients)

There are risks involved with taking any medication. Make sure you have had a conversation with your doctor about the potentially serious effects of guanfacine.

Contact your doctor IMMEDIATELY if you have any of these potentially serious side effects:

• Allergic reactions: skin rash with swelling and itching or trouble breathing or swallowing (seek emergency help immediately)
• Worsened depression (prolonged sadness) or other unusual changes in mood (discuss this with your doctor)
• Fast or slow heart rate, irregular heart beat (discuss this with your doctor)
• Increased agitation, restlessness or irritability
• Seizures or convulsions (seek emergency help immediately)
• Thoughts of self harm, hostility or suicide (discuss this with your doctor)
• Sudden onset of high blood pressure, fast heart beat, agitation, headache, stomach upset, sweating, nausea or vomiting (This may happen if guanfacine treatment is stopped suddenly. If these effects occur, seek emergency help immediately)

What precautions should my doctor and I be aware of when taking guanfacine?

Several medications can interact with guanfacine, including most high blood pressure medications; some cough and cold medications; antihistamines such as diphenhydramine (Benadryl®); medications that affect enzyme metabolism such as ketoconazole (Nizoral® tablets), carbamazepine (Tegretol®) or rifampin (Rifadin®) and several other medications including some used for sleep, anxiety, depression, seizures, or other psychiatric disorders. If you are (or begin) taking any other prescription or over-the-counter medications, including St. John’s Wort, be sure to check with your doctor or pharmacist to see if they are safe to use. Your doctor may need to change the doses of your medication(s) or monitor you carefully for side effects if you are taking medications that interact with guanfacine.

It is important to tell your doctor or pharmacist if you:

• have any allergies or have experienced a reaction to a medication.
• have diabetes or kidney problems
• have heart conditions or a family history of early heart disease or sudden death
• have psychiatric conditions such as depression, schizophrenia or bipolar disorder
• have any changes in mood or thoughts of self harm
• have Raynaud’s disease (a circulation disorder with discoloration of fingers, toes or other areas)
• miss a period, are pregnant (or are planning to become pregnant) or are breast-feeding. Tell your doctor if you become pregnant while taking guanfacine
• are currently using alcohol or street drugs (these substances can decrease how well guanfacine works for you and/or make you feel drowsy)

What special instructions should I follow while using guanfacine?

• Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests

(for example: reports from teachers, AD/HD rating scales, heart rate, blood pressure) to check how you are responding to guanfacine.

• Grapefruit (and related citrus fruits) may increase the amount of guanfacine absorbed. Talk with your doctor about whether it is safe to consume these fruits while taking this medication.
• Do not allow anyone else to use your medication.

What should I do if I forget to take a dose of guanfacine?

If you forget to take guanfacine, and it is within 4 hours of your regularly scheduled dose take it as soon as you remember. If it is more than 4 hours after your regularly scheduled dose, skip the missed dose and continue with your regular schedule. Do NOT double your next dose. If you miss more than 2 doses of guanfacine, contact your doctor. It is recommended to restart the medication at the lowest available dose, and gradually re-adjust the dose upwards.

What storage conditions are needed for guanfacine?

• Keep this medication in the original container, stored at room temperature away from moisture and heat (e.g., not in the bathroom or kitchen)
• Keep this medication out of sight and reach from children.

Share with others 

You may wish to share this information with your family members to help them to understand your treatment options. Since every person's needs are different, it is important that you follow the advice provided to you by your own doctor, nurse and/or pharmacist and speak to them if you have any questions about this medication.

About this document

Special thanks to the Kelty Centre for Mental Health for permission to adapt this document. The original document was developed by health professionals of BC Mental Health and Addiction Services, and reviewed by the staff of the Kelty Mental Health Centre. French translation provided courtesy of the Ontario Centre of Excellence for Child and Youth Mental Health.

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Disclaimer

Information in this pamphlet is offered ‘as is' and is meant only to provide general information that supplements, but does not replace the information from your health provider. Always contact a qualified health professional for further information in your specific situation or circumstance.