Starting Dose of Guanfacine for Adults with ADHD
Start guanfacine extended-release at 1 mg once daily, taken in the evening, and titrate by 1 mg per week based on response and tolerability. 1, 2, 3
Initial Dosing Protocol
- Begin with 1 mg once daily as the standard starting dose for all adults with ADHD 1, 2, 3
- Evening administration is strongly preferred over morning dosing to minimize daytime somnolence and fatigue, which are the most common adverse effects 1, 2, 3
- The medication provides around-the-clock symptom control with once-daily dosing 2
Titration Schedule
- Increase by 1 mg per week based on clinical response and tolerability 1, 2, 3
- Monitor ADHD symptoms systematically at each dose adjustment 2
- The target dose range is 0.05 to 0.12 mg/kg/day or 1 to 7 mg/day 1, 2, 3
- Maximum recommended dose is 4 mg daily in most clinical contexts, though doses up to 7 mg daily have been used 1, 3
- A practical dosing guideline is approximately 0.1 mg/kg once daily 1, 2, 3
Critical Timing Expectations
- Treatment effects require 2-4 weeks before clinical benefits are observed, unlike stimulants which work immediately 1, 2, 3
- This delayed onset is a critical counseling point to prevent premature discontinuation due to unrealistic expectations 2
- Continue titration until optimal symptom control is achieved or side effects become limiting 3
Baseline and Monitoring Requirements
- Obtain baseline blood pressure and heart rate before initiating guanfacine 2
- Obtain personal and family cardiac history before starting 1
- Consider ECG if cardiac risk factors are present 1
- Monitor vital signs regularly during dose adjustments, as small decreases in blood pressure (mean -6 to -10 mmHg) and heart rate (mean -5.5 bpm) are expected 1, 2, 4
Common Adverse Effects to Anticipate
- Somnolence/sedation (30-36%) and fatigue (14-20%) are the most frequent adverse effects, typically emerging within the first 2 weeks and often resolving by study end 2, 5, 6, 4
- Headache (26-28.5%), dry mouth, dizziness, irritability, and abdominal pain are also common 1, 2, 4
- Constipation affects 5-16% of patients with dose-dependent increases 2
- These adverse effects are typically mild to moderate, transient, and dose-related 2
Critical Safety Warning: Discontinuation
- Never abruptly stop guanfacine—it must be tapered to avoid rebound hypertension 1, 2
- Taper by 1 mg every 3-7 days when discontinuing 2
- This tapering requirement applies even though one small study in healthy young adults showed no significant rebound hypertension with abrupt cessation 7
Positioning in Treatment Algorithm
- Guanfacine is considered second-line treatment after stimulants, with effect sizes around 0.7 compared to placebo versus stimulants' effect size of approximately 1.0 1, 2
- It may be used as adjunctive therapy with stimulants when stimulant monotherapy is insufficient 1, 2
- In adults with substance use disorders, guanfacine may be preferred due to its non-controlled medication status 2
Evidence Supporting Adult Use
- While most large trials studied pediatric populations 5, 6, 4, one small crossover study in 17 adults demonstrated efficacy at an average dose of 1.10 mg (SD = 0.60), with significant improvement in ADHD symptoms and attention measures 8
- The adult study found guanfacine well-tolerated, with fatigue as the most common side effect and no discontinuations 8