Medication Information Leaflet

There are certain restrictions in the supply of Guanfacine, as it is not available in community/retail pharmacies and is only available in selected healthcare institutions via prescription from in-house doctors. Please check with your healthcare provider if they are able to supply it.

What is this medication for?

Guanfacine can be used to treat the symptoms of Attention-Deficit Hyperactivity Disorder (ADHD), alongside the use of educational, social and psychological methods.

ADHD is associated with:

  • severe inability to pay attention,
  • hyperactivity, and
  • a tendency to act without thinking

which may interfere with an individual’s ability to function in school, at work, or in social settings.

Guanfacine may be used for other conditions. Check with your healthcare professional if you are unsure why you are given this medication.

How should I take/use this medication?

  • Take your medication according to the instructions stated on the medication label.
  • Guanfacine should be taken approximately at the same time each day.
  • Do not stop taking or adjust the dose of this medication without checking with your doctor.
  • The extended-release (ER) tablet should be swallowed whole with a small amount of water, milk or other liquids. Do not crush or chew the tablets, as this may increase the rate of Guanfacine release in the body.
  • Do not change the brand of Guanfacine you are taking without informing your doctor.
  • Do not take this medication with a high fat meal as this may affect/increase the absorption of this medication.
  • It may take 2 – 4 weeks to notice the full benefits of Guanfacine, although some symptoms may improve within the first week of starting Guanfacine. Therefore, it is important to continue taking this medication as directed, even if you do not notice immediate improvement to your symptoms.
  • Do check with your doctor on how long you will have to be on this medication.

What should I do if I forget to take/use this medication?

  • If you forget to take a dose, take it as soon as you remember. However, if more than half of the time to the next dose has passed, skip the missed dose and take the next dose at your usual timing.
  • For example, for a medication to be taken two times daily at 8am and 8pm, and you missed your first dose at 8am, skip the first dose if it is after 2pm, and take your second dose at the usual timing at 8pm. Do not take two doses to make up for the missed dose.

What precautions should I take?

Inform your healthcare professional if:

  • You are allergic to this medication or any of the other ingredients of this medication
  • You are pregnant, planning to become pregnant, or breastfeeding. If you are pregnant and/or breastfeeding, your doctor would have discussed the potential benefits and side-effects with you and should you have further questions or concerns, do consult your doctor.
  • You are taking any other medications (including those that can be bought without a prescription), supplements, traditional Chinese medicine and herbal products. Some of them may affect how this medication works or cause serious drug interactions.
  • You have or have ever had:
    • Other drug allergies
    • Abnormal heart rhythm or slow heart rate
    • High or low blood pressure
    • Liver or kidney disease
    • Fainting spells
    • Any other medical conditions

Being dehydrated and overheated may increase your chance of having low blood pressure or fainting while taking Guanfacine.

  • Drink more water when you exercise, especially in hot weather.
  • If you have an infection or illness that causes heavy sweating, vomiting or diarrhoea, consult a doctor and try to drink more water.

Your doctor may need to check your blood pressure and heart rate before and during your treatment.

If you are giving Guanfacine to your child and your child’s weight changes, speak to your doctor as the dose may need to be adjusted.

If you have been taking Guanfacine in high doses and/or for a long time, do not stop taking this medication without first checking with your doctor. Your doctor may want to gradually reduce the dose before stopping completely in order to reduce unwanted adverse effects such as headache, shakiness, nervousness, feeling agitated or confused.

What are some common side-effects of this medication?

The mentioned side effects generally affect up to 10% of patients.

  • Drowsiness or feeling tired
    • Avoid driving or taking part in activities that require concentration
    • Discuss with your doctor if you can take your medication at a different time of the day
  • Difficulty sleeping
    • Discuss with your doctor if you can take your medication at a different time of the day
    • Listen to relaxing music at bedtime
    • Avoid eating or drinking too much before bedtime
    • Limit your caffeine intake (such as coffee, tea or energy drinks) at least 8 hours before bedtime
  • Nausea or vomiting, loss of appetite or stomach discomfort
    • Take the medication with or after food
    • Take small but more frequent meals, and avoid fatty or spicy food
  • Dizziness
    • Get up slowly from a sitting or lying down position
  • Headache, irritability or weakness

Most of the side effects listed here will improve with time. Speak with your doctor if any of them continues, worsens or affects your daily life.

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:

  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body

Rarely this medication may cause:

  • Severe dizziness or fainting spells
  • Chest pain or shortness of breath
  • Very slow, fast or irregular heartbeats
  • Seizures (fits)
  • Agitation, other changes in mood or behaviour
  • Thoughts of harming yourself or ending your life

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

What food or medication should I avoid when I take this medication?

Avoid drinking alcohol while taking Guanfacine, as it may make you more drowsy or less alert.

Avoid grapefruit juice/products while taking Guanfacine, as the amount of Guanfacine in the body may be increased.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack this medication into a trash bag and seal it tightly before throwing into the rubbish chute or bin.


Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Mar 2023

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