Qbrexa (Viloxazine) Trial Duration for ADHD
You should trial Qbrexa (viloxazine extended-release) for a minimum of 2 weeks to assess early response, with full efficacy evaluation at 6-8 weeks before determining treatment success or failure.
Evidence-Based Trial Timeline
Early Response Assessment (2 Weeks)
- Early response at week 2 is the best predictor of treatment success at week 6, with 75% positive predictive power and 75% sensitivity 1
- If a patient shows meaningful reduction in ADHD-RS-5 total score by week 2, they are highly likely to respond favorably by week 6 1
- This early assessment window allows clinicians to make informed decisions about continuing or adjusting treatment much sooner than traditional trial periods
Full Efficacy Evaluation (6-8 Weeks)
- Phase 2 and Phase 3 trials consistently used 8-week treatment periods to establish efficacy, with significant improvements in ADHD-RS-IV total scores observed across multiple dose groups (200-400 mg) 2
- The primary efficacy endpoint in pivotal trials was measured at week 6, demonstrating statistically significant reductions in ADHD symptom severity 1
- By 6-8 weeks, you can definitively determine whether viloxazine is providing adequate symptom control for the individual patient 2
Practical Clinical Algorithm
Week 2 Decision Point:
- Assess ADHD symptom changes using standardized rating scales
- If no improvement is observed, consider dose adjustment (can titrate by 200 mg increments weekly) 3
- If early response is present, continue current dose and reassess at week 6
Week 6-8 Decision Point:
- Evaluate full treatment response using ADHD-RS and CGI scales
- If inadequate response despite dose optimization, consider switching to alternative ADHD medication 2
- If positive response, continue maintenance therapy
Important Caveats
Dosing Considerations
- Start at 200 mg once daily and titrate by 200 mg increments at weekly intervals based on response and tolerability, with maximum dose of 600 mg/day 3
- Higher doses (300-400 mg) showed stronger effect sizes in clinical trials (ES = 0.596-0.623) compared to lower doses 2
Safety Monitoring
- Monitor closely for suicidal ideation, particularly in the first 24-48 hours after initiation or dose adjustments, especially in patients through age 24 years 3
- Watch for serotonin syndrome risk when combining with other serotonergic agents, particularly during the first 24-48 hours 4, 3
- Common side effects (somnolence, headache, decreased appetite) typically emerge early and may influence tolerability assessment 3, 2
Comparison to Other Medications
Unlike SSRIs for OCD which require 8-12 weeks for full efficacy assessment 5, viloxazine demonstrates a much faster response trajectory, making 2-week early assessment clinically meaningful and 6-8 weeks sufficient for full evaluation 1, 2.