guanfacine hydrochloride at a glance
Medicine class
Selective alpha-2A adrenergic receptor agonist; non-stimulant.
Licensed role
ADHD in children and adolescents aged 6–17 years when stimulants are unsuitable, not tolerated or ineffective.
Form
Prolonged-release tablet that must be swallowed whole.
Important effects
Can cause sleepiness, low blood pressure, a slow heart rate and fainting, particularly early in treatment or after changes.
What is guanfacine hydrochloride used for?
The prolonged-release product is licensed for:
ADHD in children and adolescents aged 6–17 years when stimulants are unsuitable, not tolerated or ineffective.
Use within comprehensive care that normally includes psychological, educational and social measures.
How does guanfacine hydrochloride work?
Guanfacine activates alpha-2A adrenergic receptors. Its action in ADHD is not fully established, but it may modify noradrenaline signalling in brain regions involved in attention, impulse control and behaviour. It also reduces sympathetic nerve activity, which can lower blood pressure and heart rate.
guanfacine hydrochloride preparations and strengths
Modified-release tablet
Route: Oral
Strengths: 1 mg, 2 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7 mg
How to take guanfacine hydrochloride
Follow the prescription and product leaflet. The prolonged-release design controls how quickly guanfacine is released.
Swallow the tablet whole with water or another suitable drink.
Do not crush, chew or break it, as this can release guanfacine too quickly.
It may be taken with or without food, but not with a high-fat meal.
Avoid grapefruit, grapefruit juice and alcohol.
Do not drive, cycle or use machinery if sleepy, dizzy or faint.
guanfacine hydrochloride side effects
Common or expected effects
- Sleepiness or sedation
- Headache
- Tiredness or lethargy
- Abdominal pain, nausea, vomiting, diarrhoea or constipation
- Dizziness, including on standing
- Low blood pressure or slow heart rate
- Reduced appetite or weight increase
- Irritability, anxiety, low mood or sleep disturbance
- Dry mouth
Get urgent medical advice
- Fainting or loss of consciousness
- Markedly slow heartbeat, severe dizziness or symptoms of very low blood pressure
- Seizure
- Severe allergic reaction
- New suicidal thoughts or behaviour
- Severe headache, confusion, agitation or tremor after abrupt withdrawal, which may indicate dangerously high blood pressure
guanfacine hydrochloride in pregnancy
Human pregnancy data are limited, and guanfacine is not recommended during pregnancy. Anyone who is pregnant, planning pregnancy or not using contraception should discuss treatment promptly with the prescriber.
guanfacine hydrochloride while breastfeeding
It is unknown whether guanfacine passes into human milk, and a risk to a breastfed child cannot be excluded. The prescriber and breastfeeding specialist should weigh the benefits of breastfeeding against the need for treatment.
guanfacine hydrochloride interactions
Tell the prescriber or pharmacist about all medicines, supplements and herbal products. Important examples include:
Strong or moderate CYP3A4/5 inhibitors, including clarithromycin, azole antifungals and some antivirals
Can increase guanfacine exposure and the risk of sleepiness, low blood pressure and a slow heart rate.
Grapefruit or grapefruit juice
Can increase guanfacine exposure and should be avoided.
CYP3A4 inducers, including carbamazepine, phenytoin, rifampicin and St John’s wort
Can lower guanfacine exposure and reduce its effect.
Common questions about guanfacine hydrochloride
Answers are fully visible for fast scanning and source review.
Is guanfacine hydrochloride a stimulant?
No. It is a non-stimulant alpha-2A adrenergic receptor agonist.
Can adults take it for ADHD?
The safety and effectiveness of the prolonged-release product for adult ADHD have not been established, and this use is outside its stated UK licence.
Can the tablets be crushed?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.