guanfacine hydrochloride: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
guanfacine hydrochloride: clinical details
Prescribing considerations
- Initiate under an appropriate specialist in childhood or adolescent behavioural disorders.
- Confirm that stimulants are unsuitable, not tolerated or ineffective, and embed treatment within comprehensive ADHD care.
- Assess cardiovascular and psychiatric history, concomitant medicines, family history of sudden or unexplained death, and risks of sedation, hypotension, bradycardia, QT prolongation and weight gain.
- Review carefully in hepatic or severe renal impairment.
- Warn patients and caregivers about sedation, syncope, withdrawal effects, aggression and suicide-related events.
Contraindications and cautions
- Hypersensitivity to guanfacine or any excipient.
- The product contains lactose and is unsuitable in certain rare hereditary disorders of galactose metabolism.
- Use particular caution with hypotension, bradycardia, heart block, cardiovascular disease, syncope, dehydration, QT prolongation or risk factors for torsade de pointes.
Monitoring
- Record baseline blood pressure, pulse, height, weight and BMI.
- Monitor sedation, blood pressure and heart rate closely during initiation and after treatment changes.
- Continue growth, weight, cardiovascular and clinical-response monitoring.
- Monitor for new aggression, hostility, suicidal thoughts or behaviour.
Clinical pharmacology
Guanfacine is a selective alpha-2A adrenergic receptor agonist and CYP3A4/5 substrate. It is absorbed gradually from the prolonged-release formulation, undergoes hepatic metabolism and renal elimination, and reduces sympathetic outflow, blood pressure and heart rate.
Formulation and product differences
- The prolonged-release tablet must be swallowed whole.
- Immediate-release guanfacine must not be substituted milligram-for-milligram because its pharmacokinetic profile differs.
- The product contains lactose and is essentially sodium-free.
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
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.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.