Guanfacine is used on its own or together with other medicines to keep your blood pressure under control. It relaxes your blood vessels which helps to lower your blood pressure.
This medicine is also used to treat attention deficit hyperactivity disorder (ADHD) in children. ADHD is a behavioural condition characterised by inattentiveness, hyperactivity, and impulsiveness.
Guanfacine is meant to be taken as part of a complete ADHD care programme which includes psychological, educational, and social measures.
Take Guanfacine exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
Guanfacine is available as a conventional tablet or extended-release tablet.
If you are taking the conventional tablet, it is best taken in the evening before bedtime.
If you are taking the extended-release type of tablet (usually labelled as "ER"), you may take it with or without food. Swallow it whole. Do not divide, chew, or crush the tablet.
Try to take it at the same time each day.
Your doctor will also discuss the use of this medicine as different preparations of Guanfacine may only be used for a specific condition.
Do not take this medicine for any conditions other than what is prescribed by your doctor.
Guanfacine must be taken regularly for it to be effective. Continue taking this medicine even when you feel better. Do not stop taking it suddenly as this may worsen your condition.
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.
DO NOT double a dose under any circumstances.
If you often forget to take your medicine, let your doctor and pharmacist know.
Inform your doctor if you have the following conditions:
- current or history of heart disease e.g. recent heart attack, low blood pressure, slow heartbeat, heart rhythm disorder
- cerebrovascular disease (disease of the blood vessels supplying the brain)
- history of or conditions that may cause fainting or passing out e.g. dehydration (excessive water loss from the body)
- history of QT prolongation
- kidney disease
- liver disease
Let your doctor know if you are pregnant or breastfeeding.
Be sure to check with your doctor or pharmacist before giving Guanfacine to a child and the elderly. Children and elderly people may be more sensitive to the side effects.
If you are going to have certain laboratory tests (e.g. blood test for adrenal gland function), inform your doctor that you are taking this medicine.
Do not switch dosage forms unless instructed by your doctor. This is because different dosage forms of Guanfacine may have slightly different ways of working in your body.
Keep your appointments with your doctor. Your doctor needs to monitor your condition and check your response to the medication regularly.
Your blood pressure may fall to unsafe levels without you noticing it. Monitor your blood pressure and heart rate regularly before, during, and after treatment.
What lifestyle changes can I make to improve my blood pressure?
Regular exercise and eating a healthy diet will help control your blood pressure and improve your overall health. Engage in physical activity like walking for at least 30 to 60 minutes on most days of the week. If you have not exercised for a long time, start with light exercises such as slow walks. Speak to your doctor about what type of exercise would be suitable for you. Follow a healthy diet plan by eating more fruits, vegetables, whole grains and low-fat dairy products and reduce your intake of foods high in saturated fat, cholesterol and sodium. Cutting down on deep-fried foods and using less salt when cooking can kick-start your healthy diet.
If you smoke, you should try to quit. Smoking is harmful to your blood pressure, heart and overall health. Speak to your doctor or pharmacist about ways to stop your smoking habit.
Guanfacine may cause dizziness and drowsiness. If affected, do not drive or take part in any activity in which you need to be alert.
This medicine may cause your blood pressure to fall suddenly when you get up from a sitting or lying down position and you may feel giddy. To minimise this problem, stand up slowly.
Other side effects include any of the following: nausea, vomiting, diarrhoea, stomach pain, constipation, indigestion, dry mouth, decreased appetite, tiredness, generalised weakness or lack of energy, fever, irritable, difficulty sleeping, itching, and rash.
Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
- temporary loss of consciousness, fainting or passing out
- signs of withdrawal symptoms e.g. headache, agitation, confusion, nervousness, tremors
- aggressive behaviour
- slow heartbeat
- having thoughts of self-harm
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Inform your doctor and pharmacist if you are taking any of these medicines:
- other medicines for high blood pressure e.g. propranolol, prazosin
- medicines for epilepsy (fits or seizures) e.g. valproic acid, phenobarbital, phenytoin
- medicines for HIV infection e.g. efavirenz, etravirine
- medicines to treat fungal infection e.g. ketoconazole, fluconazole
- medicines for mood disorders
- medicines for sleep disorder
- water pills or medicines for water retention
- rifampicin (medicine to treat TB [an infection known as tuberculosis])
This list does not include all medicines that may interact with Guanfacine.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements, and medicines that you buy without a prescription.
If you are taking the extended-release type of tablet, avoid taking Guanfacine together with high-fat foods. Ask your doctor about the types of food you should avoid.
Avoid excessive consumption of grapefruit or grapefruit juice (more than 1 litre a day).
Avoid alcohol. Alcohol intake may worsen the dizziness and drowsiness caused by Guanfacine.
Store in a cool, dry place away from the reach of children.
Medicines must not be used past the expiry date.
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