What is the starting dose of guanfacine for attention deficit hyperactivity disorder (ADHD) and hypertension?

Starting Dose of Guanfacine for ADHD and Hypertension

The recommended initial dose of guanfacine is 1 mg once daily, given at bedtime for hypertension and in the morning for ADHD. 1, 2

Dosing for Hypertension

• Initial dose: 1 mg daily at bedtime to minimize somnolence 1
• Titration: If after 3-4 weeks the 1 mg dose is insufficient, may increase to 2 mg daily 1
• Maximum dose: Although higher doses have been used, adverse reactions increase significantly with doses above 3 mg/day 1
• Most therapeutic effect is seen at the 1 mg dose 1

Dosing for ADHD

• Initial dose: 1 mg once daily 2
• Titration: Increase by 1 mg weekly based on response and tolerability 2
• Target dose range: 0.05 to 0.12 mg/kg/day or 1 to 7 mg daily 2
• Extended-release formulation is preferred for better tolerability 3

Important Considerations

• Receptor Specificity: Guanfacine is selective for alpha-2A receptors, making it less sedating than clonidine 3

• Side Effect Profile: Common side effects include:

  • Somnolence (38.6%)
  • Headaches (20.5%)
  • Fatigue (15.2%)
  • Dry mouth 4

• Cardiovascular Effects:

  • Modest reductions in blood pressure and heart rate are common 5
  • Baseline assessment of personal and family cardiac history is recommended 3
  • ECG should be considered if cardiac risk factors are present 3

• Discontinuation:

  • Should not be stopped abruptly if taken for more than 9 weeks due to risk of rebound hypertension 3
  • When discontinued abruptly, blood pressure typically returns to pretreatment levels slowly (within 2-4 days) 1

Special Populations

• Pregnancy: Limited information available; use with caution after risk-benefit discussion 2, 3
• Breastfeeding: No published studies of guanfacine while breastfeeding; caution is advised 2

Efficacy Data

• Guanfacine has demonstrated efficacy for ADHD treatment with a response rate of 58.5% vs 29.4% for placebo in short-term trials (<10 weeks) 4
• For longer treatment periods (>10 weeks), efficacy rates were 63.6% vs 39.7% for placebo 4

Pitfalls to Avoid

• Do not substitute immediate-release guanfacine for extended-release on a milligram-for-milligram basis due to different pharmacokinetics 6
• Monitor for orthostatic hypotension, which can occur even with delayed onset (up to 30 hours after overdose) 7
• Be aware that QTc prolongation has been reported in overdose cases 7