From the Guidelines
Guanfacine is recommended for ADHD and hypertension, with a typical starting dose of 1 mg once daily for ADHD and 1 mg daily for hypertension, with gradual increases as needed and under medical supervision. The medication should be taken at the same time each day, with or without food, and should not be crushed or chewed. For ADHD, the extended-release form (Intuniv) is typically used, while for hypertension, the immediate-release form (Tenex) is usually prescribed 1. Guanfacine works by stimulating alpha-2A adrenergic receptors in the prefrontal cortex, enhancing working memory and attention in ADHD, while its effects on the sympathetic nervous system reduce blood pressure in hypertension 1. Some key points to consider when prescribing guanfacine include:
- Starting with a low dose and gradually increasing as needed and under medical supervision
- Monitoring for common side effects such as drowsiness, fatigue, dry mouth, and dizziness
- Avoiding abrupt discontinuation, as this can cause rebound hypertension
- Tapering the dosage gradually under medical supervision if discontinuation is necessary
- Considering alternative therapies or adjusting the dosage regimen to minimize adverse effects and optimize treatment outcomes 1. It's also important to note that guanfacine has been shown to be effective in reducing core symptoms of ADHD, with an effect size of approximately 0.7, and has been approved for use as an adjunctive therapy with stimulant medications 1. Overall, guanfacine is a valuable treatment option for ADHD and hypertension, offering a unique mechanism of action and a range of benefits, but its use should be carefully managed and monitored to minimize potential risks and optimize treatment outcomes.
From the FDA Drug Label
The recommended initial dose of guanfacine tablets, USP when given alone or in combination with another antihypertensive drug is 1 mg daily given at bedtime to minimize somnolence
- Recommended Dosage: The recommended initial dose of guanfacine is 1 mg daily given at bedtime.
- Use for ADHD and Hypertension: Guanfacine is used for the treatment of hypertension, but the provided drug labels do not directly support its use for attention deficit hyperactivity disorder (ADHD) at the specified dosages.
- Dosage Adjustment: If after 3 to 4 weeks of therapy 1 mg does not give a satisfactory result, a dose of 2 mg may be given, although most of the effect of guanfacine hydrochloride is seen at 1 mg.
- Maximum Daily Dose: Higher daily doses have been used, but adverse reactions increase significantly with doses above 3 mg/day. 2
From the Research
Guanfacine Dosage and Use
- Guanfacine is an alpha(2a)-adrenoreceptor agonist used to treat attention-deficit/hyperactivity disorder (ADHD) and hypertension 3, 4.
- The recommended dosage of guanfacine for ADHD is up to 4 mg/d, with a dose-response relationship for efficacy 5.
- For hypertension, daily dosages of guanfacine 1,2, and 3 mg (as the hydrochloride salt) were comparable in efficacy 6.
- Guanfacine extended release (GXR) is a once-daily formulation that has been shown to be efficacious in improving ADHD in children 4, 5.
Administration and Tolerability
- Guanfacine can be administered once daily, with a slow elimination half-life contributing to its long duration of action 6.
- The most common adverse effects associated with guanfacine and GXR treatment are sedation, somnolence, and hypersomnia, which are typically mild to moderate and tend to diminish with continued treatment 4, 5.
- Cardiovascular effects, such as hypotension and bradycardia, are common but generally modest in nature 3, 5.
- Supratherapeutic serum guanfacine concentrations may induce QT prolongation, although this is rare 7.
Special Considerations
- Guanfacine should not be discontinued abruptly, as this may lead to rebound hypertension 3.
- Dose substitution on a milligram-for-milligram basis between immediate-release guanfacine and GXR is inappropriate due to differences in pharmacokinetics 5.
- Guanfacine may be used as monotherapy or adjunctive therapy to psychostimulant medications for ADHD 5.