Duration of Action of Intuniv (Guanfacine Extended-Release)
Intuniv provides "around-the-clock" symptom control lasting approximately 24 hours with once-daily dosing, though the approved dosing generally provides symptom benefit lasting 8-14 hours, and up to 24 hours in some children and adolescents receiving higher doses. 1, 2
Pharmacological Duration Profile
Key distinction from stimulants:
- Unlike stimulants (methylphenidate, amphetamines) which provide clinical benefits for only 3-5 hours with immediate-release formulations, guanfacine extended-release offers continuous coverage throughout the day and night 1
- This "around-the-clock" effect is a major advantage over stimulants, which have limited daily duration of effects and potential for afternoon/evening rebound symptoms 1
Onset vs. Duration: Critical Timing Considerations
Delayed therapeutic onset:
- Treatment effects are not observed immediately—guanfacine requires 2-4 weeks before clinical benefits become apparent 1, 3
- This contrasts sharply with stimulants, which work immediately after administration 1
- One study suggests improvement in core symptoms may occur within 3 weeks 4
This delayed onset is a critical counseling point for families—expectations must be set appropriately to prevent premature discontinuation due to lack of immediate response 3
Optimal Dosing Timing
Evening administration is generally preferable due to the relatively frequent occurrence of somnolence and fatigue as adverse effects 1, 3
- However, no significant difference in efficacy was found between morning versus evening administration in controlled studies 1
- Evening dosing helps minimize daytime sedation that could interfere with school performance and daily activities 3
Dosing Specifications
Weight-based dosing regimen:
- Starting dose: 1 mg once daily 1, 3
- Titration: Increase by 1 mg per week based on response and tolerability 1, 3
- Target range: 0.05-0.12 mg/kg/day or 1-7 mg/day 1, 3
- Maximum dose: 6-7 mg/day depending on jurisdiction 1
Long-Term Maintenance of Effect
Sustained efficacy documented:
- Longer-term maintenance of treatment effects is documented for guanfacine in extension studies 1
- Improvements in ADHD symptoms and functional impairment were sustained over 24 months in open-label extension trials 3
Common Pitfalls to Avoid
Critical discontinuation warning:
- Never abruptly stop guanfacine—it must be tapered by 1 mg every 3-7 days to avoid rebound hypertension 3
- This is essential even at low doses, as individual responses vary 3
Monitoring requirements:
- Baseline blood pressure and heart rate should be obtained before initiation 3
- Cardiovascular parameters should be monitored during dose adjustments 3
- Most common adverse effects are somnolence (38.6-50.7%), headache (20.5-22.1%), and fatigue (15.2%) 5, 6
Clinical Context
Second-line positioning:
- Current guidelines generally recommend guanfacine as second-line treatment after stimulants due to smaller effect sizes (medium range vs. large for stimulants) 1
- However, guanfacine may be preferred as first-line in specific scenarios: comorbid sleep disorders, substance use disorders, disruptive behavior disorders, or tic/Tourette's disorder 1