Products
Guanfacine is commercially available in the form of sustained-release tablets (Intuniv). It has been approved in the United States since 2009, in the EU since 2015, and in many countries since 2017.
Structure and properties
Guanfacine (C9H9Cl2N3O, Mr = 246.1 g/mol) is a phenylacetyl guanidine derivative. It is present in drugs as guanfacine hydrochloride, a white crystalline powder that is sparingly soluble in water.
Effects
Guanfacine (ATC C02AC02) is effective against ADHD symptomatology. It is a selective central adrenergic alpha2A receptor agonist and is not a stimulant like amphetamines. Guanfacine affects noradrenergic neurotransmission. It was originally developed as an antihypertensive agent and has additional antihypertensive properties (cf. clonidine). The half-life is approximately 18 hours.
Indications
For the treatment of attention-deficit/hyperactivity disorder ADHD in children and adolescents 6-17 years of age. Guanfacine is approved as a second-line agent after stimulants.
Dosage
According to the SmPC. Tablets are taken once daily at the same time of day, regardless of meals, either in the morning or evening. The dose is adjusted individually. Do not take with a high-fat meal or with grapefruit juice.
Abuse
Unlike stimulants, guanfacine is not a narcotic and is not abused as an intoxicant.
Contraindications
- Hypersensitivity
For complete precautions, see the drug label.
Interactions
Guanfacine is a substrate of CYP3A and corresponding drug interactions with CYP inhibitors and inducers are possible. Guanfacine should be combined only with caution with antihypertensives and centrally depressant drugs. Other interactions are possible.
Adverse effects
The most common adverse effects include drowsiness, headache, fatigue, abdominal pain, and dullness. Guanfacine can lower blood pressure and heart rate to brief unconsciousness.
