What is the recommended dose of guanfacine (Extended Release) for an 8-year-old patient with Attention Deficit Hyperactivity Disorder (ADHD) weighing 100 pounds?

Guanfacine ER Dosing for 100-pound, 8-Year-Old with ADHD

For this 8-year-old patient weighing 100 pounds (45.4 kg), start guanfacine ER at 1 mg once daily in the evening, then titrate by 1 mg weekly to a target dose of 4-5 mg daily (approximately 0.1 mg/kg), with a maximum of 4 mg in most clinical contexts. 1, 2

Weight-Based Dosing Calculation

• This child weighs 100 pounds = 45.4 kg 1
• The recommended weight-adjusted dose is 0.1 mg/kg once daily, which equals approximately 4.5 mg for this patient 1, 2
• The target dose range is 0.05 to 0.12 mg/kg/day, meaning 2.3-5.4 mg/day for this specific patient 1, 2
• The practical target dose would be 4 mg daily, as this is the highest commonly approved dose and falls within the optimal weight-based range 1, 2

Titration Schedule

• Start with 1 mg once daily in the evening 1, 2
• Increase by 1 mg per week based on clinical response and tolerability 1, 2
• Week 1: 1 mg daily
• Week 2: 2 mg daily
• Week 3: 3 mg daily
• Week 4: 4 mg daily (target dose for this weight) 1, 2

Timing of Administration

• Evening administration is strongly preferred to minimize daytime somnolence and fatigue, which are the most common adverse effects 1
• The medication provides around-the-clock symptom control with once-daily dosing 1

Critical Counseling Points

• Therapeutic effects require 2-4 weeks to become apparent, unlike stimulants which work immediately—set appropriate expectations to prevent premature discontinuation 1
• Somnolence and fatigue are the most common side effects, occurring in 15-20% of patients, and typically resolve over time 1, 3
• Headache affects approximately 20% of patients 1

Mandatory Monitoring

• Obtain baseline blood pressure and heart rate before starting guanfacine 1, 2
• Monitor cardiovascular parameters at each dose adjustment, as guanfacine causes modest decreases in BP (1-4 mmHg) and HR (1-2 bpm) 1, 2
• Obtain personal and family cardiac history, specifically asking about unexplained fainting, Wolf-Parkinson-White syndrome, or sudden cardiac death 1, 2
• Monitor ADHD symptoms systematically at each dose adjustment using parent and teacher reports 1

Critical Safety Warning

• Never abruptly discontinue guanfacine—it must be tapered by 1 mg every 3-7 days to avoid rebound hypertension 1, 2

Higher Dose Considerations

• While doses up to 7 mg/day have been studied, and weight-adjusted doses of 0.12 mg/kg may provide additional clinical benefits if tolerated, the maximum approved dose is typically 4 mg daily in most clinical contexts 1, 2, 4
• For this 45.4 kg patient, 0.12 mg/kg would equal 5.4 mg, but staying at 4 mg is the standard recommendation unless inadequate response warrants careful escalation under close monitoring 1, 4

Common Pitfall to Avoid

• Do not expect immediate results—guanfacine is a second-line agent with smaller effect sizes (0.7) compared to stimulants (1.0), and requires patience with the 2-4 week onset period 1