Adderall XR 15mg to Vyvanse Dose Conversion
The equivalent dose of Vyvanse for Adderall XR 15mg is approximately 37.5mg, though in clinical practice you should start with either 30mg or 40mg Vyvanse (the closest available strengths) and titrate based on response. 1
Conversion Algorithm
Apply a 2.5:1 conversion ratio (Vyvanse:Adderall) when switching between these medications. 1
- For Adderall XR 15mg: multiply by 2.5 to get 37.5mg Vyvanse equivalent 1
- Since Vyvanse comes in 10mg increments, round to the nearest available strength (30mg or 40mg) 1
- Start with 30mg Vyvanse if concerned about tolerability, or 40mg if prioritizing symptom control 1
Pharmacokinetic Rationale
The conversion factor accounts for the prodrug nature of lisdexamfetamine (Vyvanse):
- Vyvanse is hydrolyzed in the blood to release d-amphetamine gradually, resulting in a delayed Tmax (peak concentration occurs approximately 1 hour later than immediate d-amphetamine) 2, 3
- Despite the delayed onset, total amphetamine exposure (AUC) is equivalent between equimolar doses of lisdexamfetamine and d-amphetamine 2
- The therapeutic duration of Vyvanse extends to at least 13 hours post-dose, potentially longer than other long-acting formulations 3
Titration After Conversion
Adjust the Vyvanse dose in 10mg increments at weekly intervals if needed, up to a maximum of 70mg daily. 1
- Monitor for both efficacy (ADHD symptom control) and tolerability at each adjustment 4
- Allow at least one week between dose increases to properly evaluate response 4
- The usual starting dose range for Vyvanse is 20-30mg once daily, with weekly 10mg increases as needed 1
Monitoring Parameters After Conversion
- Assess blood pressure and pulse at follow-up visits (quarterly for adults) 4
- Monitor weight at each visit to detect appetite suppression 4
- Evaluate target ADHD symptoms and common side effects including insomnia, anorexia, headaches, and social withdrawal 4
- Morning administration is essential to minimize sleep disturbances 4
Common Pitfalls to Avoid
- Do not assume a 1:1 conversion ratio - this will result in underdosing, as the appropriate ratio is 2.5:1 1
- Failing to account for the delayed onset of Vyvanse may lead to premature dose escalation before adequate time for assessment 2
- Not allowing sufficient time (at least one week) between dose adjustments to evaluate response 4
- Continuing to increase beyond 70mg maximum when ineffective - consider alternative medications instead 4, 1