Adderall XR 50mg to Vyvanse Dose Conversion
The equivalent dose of Vyvanse for Adderall XR 50mg is approximately 125mg, but since the maximum approved dose of Vyvanse is 70mg, you should start at 70mg Vyvanse (the maximum dose) when converting from Adderall XR 50mg. 1, 2
Conversion Rationale
The conversion between these medications is based on a 2.5:1 ratio (Vyvanse:Adderall) when switching formulations. 3 This means:
- Adderall XR 20mg = Vyvanse 50mg 3
- Adderall XR 50mg would theoretically = Vyvanse 125mg
However, this calculation exceeds the maximum approved dose.
Practical Dosing Approach
Since the calculated equivalent exceeds the maximum:
- Start at Vyvanse 70mg once daily in the morning (the maximum approved dose) 1
- The maximum recommended daily dose of Adderall XR for adults is 50mg 2
- The maximum approved daily dose of Vyvanse is 70mg 1
Important Pharmacokinetic Differences
While both medications deliver amphetamine, there are key differences to consider:
- Lisdexamfetamine (Vyvanse) is a prodrug that requires hydrolysis in the body to release active d-amphetamine, resulting in a delayed onset compared to Adderall XR 4, 5
- Peak plasma concentrations occur approximately 1 hour later with lisdexamfetamine compared to d-amphetamine 6
- Both medications provide similar total amphetamine exposure (AUC) at equivalent doses, but with different time profiles 6
Monitoring After Conversion
When switching from Adderall XR 50mg to Vyvanse 70mg:
- Assess clinical response and tolerability within 2-4 weeks of the conversion 1
- Monitor for both therapeutic effects and side effects, including insomnia, anorexia, headaches, and weight loss 1
- Check vital signs (blood pressure and pulse) after the medication change 2
- Use standardized ADHD rating scales to objectively assess symptom control 2
Alternative Strategies if Inadequate Response
If symptom control is inadequate at Vyvanse 70mg:
- Consider switching to a different stimulant formulation or adding a non-stimulant medication like atomoxetine 2
- Reevaluate the diagnosis and assess for comorbid conditions affecting treatment response 2
- Rule out other factors contributing to perceived lack of efficacy, such as sleep issues or medication adherence 2
Common Pitfall to Avoid
Do not attempt to exceed the 70mg maximum dose of Vyvanse to achieve a theoretical equivalent, as this exceeds FDA-approved dosing and increases risk of adverse cardiovascular and psychiatric effects. 1