Guanfacine ER Dosage
For ADHD (Children and Adolescents, Ages 6-17)
Start guanfacine extended-release at 1 mg once daily in the morning, titrate by 1 mg weekly based on response and tolerability, with a typical maintenance dose of 1-4 mg/day and a maximum of 4 mg/day 1, 2.
Dosing Algorithm:
- Starting dose: 1 mg once daily (morning administration)
- Titration schedule: Increase by 1 mg increments weekly
- Maintenance range: 1-4 mg/day
- Maximum dose: 4 mg/day (FDA-approved)
Weight-Based Considerations:
Research suggests that weight-adjusted doses of 0.08-0.12 mg/kg may provide optimal clinical benefit 3. For adolescents weighing >70 kg, this may theoretically require doses exceeding 4 mg, but such dosing remains investigational and is not currently FDA-approved 3.
Important Caveats:
- Monotherapy vs. adjunctive therapy: Guanfacine ER is FDA-approved both as monotherapy and as adjunctive therapy with stimulants for ADHD 1
- Somnolence management: Most common adverse effects (somnolence, dizziness, bradycardia) are dose-dependent and typically resolve over time 1, 2
- Cardiovascular monitoring: Obtain personal and family cardiac history before initiation; monitor blood pressure and heart rate regularly, as guanfacine ER causes dose-dependent decreases in both parameters 1, 3
Drug-Drug Interactions:
- With moderate/strong CYP3A4 inhibitors (e.g., erythromycin, fluconazole): Reduce guanfacine ER dose to 50% of usual target dose 4
- With moderate/strong CYP3A4 inducers (e.g., efavirenz): Consider titrating up to double the usual target dose over 1-2 weeks 4
For Hypertension (Adults)
Start guanfacine immediate-release at 1 mg once daily at bedtime, and if inadequate response after 3-4 weeks, increase to 2 mg daily; maximum dose is 3 mg/day 5.
Dosing Algorithm:
- Starting dose: 1 mg once daily at bedtime
- Titration timing: Reassess after 3-4 weeks
- Maintenance dose: 1-2 mg/day (most effect seen at 1 mg)
- Maximum dose: 3 mg/day (adverse reactions increase significantly above this dose) 5
Critical Safety Point:
Do NOT confuse formulations—immediate-release (IR) for hypertension and extended-release (ER) for ADHD are NOT interchangeable. A case report documented severe bradycardia and hypotension requiring ICU admission when a child received IR instead of ER formulation 6.
Discontinuation Protocol
Taper guanfacine gradually rather than stopping abruptly to avoid rebound hypertension 1, 5.
- Rebound risk: While rebound hypertension is less frequent with guanfacine than clonidine, it can occur 2-4 days after abrupt cessation 5
- Tapering schedule: Research supports gradual dose reduction over 4-10 days (e.g., decrease by 1 mg every 3-4 days) 7
- Blood pressure monitoring: Most patients return to pretreatment levels within 2-4 days without ill effects when tapered appropriately 5, 7