How do I increase the dosage of guanfacine (Extended Release) for Attention Deficit Hyperactivity Disorder (ADHD)?

Guanfacine ER Dose Titration for ADHD

Start at 1 mg once daily and increase by 1 mg per week based on response and tolerability, targeting a dose range of 0.05-0.12 mg/kg/day (typically 1-7 mg/day), with evening dosing preferred to minimize daytime somnolence. 1

Initial Dosing Strategy

• Begin with 1 mg once daily, preferably administered in the evening due to the relatively frequent occurrence of somnolence and fatigue 1
• The starting dose should be maintained for at least one week before any adjustment 1

Titration Schedule

• Increase by 1 mg increments weekly based on clinical response and tolerability 1, 2
• Monitor ADHD symptoms systematically at each dose adjustment using parent and teacher reports 3
• The typical therapeutic range is 1-4 mg/day in most clinical trials, though doses up to 7 mg/day may be used 1, 2, 4

Target Dosing

• Weight-based dosing: Aim for 0.05-0.12 mg/kg/day or approximately 0.1 mg/kg once daily 1
• Fixed dosing: Most patients respond to 1-4 mg/day, with effect sizes ranging from 0.43 to 0.62 across this dose range 4
• Maximum recommended dose is 7 mg/day 1

Monitoring During Titration

• Assess blood pressure and heart rate at each dose adjustment, as guanfacine causes dose-dependent decreases in these parameters 5, 4
• Small mean decreases in pulse, systolic, and diastolic blood pressure occur with dose escalation but typically stabilize during maintenance 5
• Evaluate for somnolence, sedation, and fatigue, which typically emerge within the first 2 weeks but generally resolve by study end 4

Important Considerations

Drug Interactions Requiring Dose Adjustment

• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): Reduce guanfacine dose by half when adding potent inhibitors 6
• CYP3A4 inducers (e.g., rifampin, carbamazepine): Double the guanfacine dose when adding potent inducers, though correction factors may need to be higher based on clinical experience 6

Common Pitfalls to Avoid

• Do not increase doses too rapidly: Weekly increments allow adequate time to assess response and minimize adverse effects 1
• Do not abruptly discontinue: Taper gradually to avoid rebound hypertension and withdrawal effects, which can occur 2-4 days after discontinuation 1, 7
• Do not exceed 4 mg/day without careful consideration: Most efficacy is achieved at 1-4 mg/day, and adverse effects increase at higher doses 2, 4

Adjunctive Use with Stimulants

• When adding guanfacine to ongoing stimulant therapy for suboptimal response, the same titration schedule applies (1 mg weekly increments up to 4 mg/day) 5
• Both morning and evening dosing of guanfacine are effective when combined with morning stimulants, though evening dosing may reduce daytime sedation 5