Vyvanse to Adderall Dose Conversion
When converting from Adderall to Vyvanse, use an approximate 2.5:1 ratio (Vyvanse:Adderall), meaning 20mg of Adderall converts to approximately 50mg of Vyvanse. 1
Conversion Algorithm by Adderall Dose
For Adderall 20mg Daily
- Start with Vyvanse 50mg once daily in the morning 1
- This represents the standard 2.5:1 conversion ratio 1
For Adderall XR 30mg Daily
- Start with Vyvanse 50mg once daily in the morning 2
- This represents a conservative 1:1.67 conversion ratio that accounts for the prodrug metabolism of lisdexamfetamine 2
For Other Adderall Doses
- Apply the 2.5:1 conversion factor (Vyvanse:Adderall) as a starting point 1
- Do not exceed the FDA-approved maximum of 70mg Vyvanse daily 2, 1
Critical Administration Requirements
Morning dosing is mandatory to minimize sleep disturbances 2
Allow at least one week on the initial conversion dose before making any adjustments to properly evaluate response 2
Post-Conversion Titration Protocol
If symptom control remains inadequate after one week:
- Increase by 10mg weekly increments 2, 1
- Maximum dose is 70mg daily 2, 1
- Continue weekly increments until adequate symptom control or maximum dose reached 2
Mandatory Monitoring Parameters
At the first follow-up visit after conversion, assess:
- Blood pressure and pulse 2
- Target ADHD symptoms using standardized rating scales 2
- Weight at each visit to detect appetite suppression 2
Pharmacologic Rationale for Conversion
The conversion ratio accounts for lisdexamfetamine being a prodrug that requires hydrolysis to active d-amphetamine through rate-limited enzymatic biotransformation in the blood 3, 4. This prodrug design provides approximately 12 hours of duration with once-daily dosing 5, compared to Adderall's shorter duration requiring multiple daily doses 6.
Common Pitfalls to Avoid
- Do not use a 1:1 conversion ratio - this will result in underdosing, as Vyvanse requires higher milligram amounts due to its prodrug nature 2, 1
- Do not adjust doses more frequently than weekly - the full therapeutic effect requires time to assess 2
- Do not dose Vyvanse in the afternoon or evening - this will cause insomnia 2