Guanfacine Extended-Release for 24-Hour Coverage
Guanfacine extended-release (ER) is the formulation designed for 24-hour coverage, administered once daily, whereas immediate-release guanfacine requires multiple daily doses and lacks consistent around-the-clock symptom control. 1, 2
Formulation Comparison
Extended-release guanfacine provides continuous coverage throughout the day and night with once-daily dosing, offering a major advantage over the immediate-release formulation which requires multiple daily doses. 1 The ER formulation delivers "around-the-clock" symptom control lasting approximately 24 hours, making it the clear choice when 24-hour coverage is required. 1
Pharmacokinetic Profile Supporting 24-Hour Coverage
- The extended-release formulation maintains therapeutic plasma concentrations over 24 hours with a single daily dose, with an elimination half-life averaging 17 hours (range 10-30 hours) in adults. 3
- Peak plasma concentrations occur 2.6 hours after dosing on average, with steady-state blood levels attained within 4 days in most patients. 3
- The ER formulation demonstrates linear pharmacokinetics, with predictable dose-proportional increases in exposure. 4
Dosing Specifications for Extended-Release
Start with 1 mg once daily, then titrate by 1 mg per week based on clinical response and tolerability, with a target dose range of 0.05-0.12 mg/kg/day or 1-7 mg/day. 1, 2 The maximum recommended dose is typically 4 mg daily in most clinical contexts, though doses up to 7 mg daily have been used. 2
Optimal Timing of Administration
Evening administration is generally preferable because somnolence and fatigue are the most common adverse effects, and evening dosing helps minimize daytime sedation. 1, 2 However, the medication can be taken either morning or evening with equivalent efficacy—the key is consistent once-daily dosing. 1
Clinical Efficacy Timeline
Treatment effects require 2-4 weeks before clinical benefits become apparent, unlike stimulants which work immediately. 1, 2 This delayed onset is a critical counseling point to prevent premature discontinuation due to unrealistic expectations. 1
Critical Safety Considerations
- Never discontinue guanfacine abruptly—it must be tapered by 1 mg every 3-7 days to avoid rebound hypertension. 1, 2 This applies even when switching to another medication. 5
- Obtain baseline blood pressure and heart rate before initiation, then monitor at each dose adjustment. 1 Expect modest decreases of 1-4 mmHg in blood pressure and 1-2 bpm in heart rate. 1
- The most common adverse effects are somnolence (most frequent reason for discontinuation), fatigue, headache, and constipation. 1, 6
Comparison to Immediate-Release Formulation
The immediate-release formulation was originally developed for hypertension and requires multiple daily doses (typically twice daily), making it impractical for ADHD management where consistent 24-hour symptom control is desired. 3, 7 The ER formulation was specifically developed to address this limitation and has been shown to be more effective for long-term ADHD management with fewer adverse effects compared to immediate-release. 8