Converting Adderall to Vyvanse
Start with Vyvanse 50 mg once daily in the morning. This patient is taking a total of 30 mg of amphetamine base daily (20 mg Adderall XR + 10 mg Adderall IR), and a reasonable conversion approach is to use approximately 1.5-2 times the total daily Adderall dose when switching to Vyvanse 1, 2.
Conversion Rationale
The conversion is based on the following pharmacological principles:
Lisdexamfetamine (Vyvanse) is a prodrug that is enzymatically converted to dextroamphetamine after oral administration 2. This conversion occurs predominantly in red blood cells, resulting in a slower onset and longer duration of action compared to immediate-release amphetamines.
Adderall contains 75% dextroamphetamine and 25% levoamphetamine salts, while Vyvanse converts entirely to dextroamphetamine. This means 30 mg of Adderall provides approximately 22.5 mg of dextroamphetamine base.
The typical conversion ratio used in clinical practice is approximately 1.5-2:1 (Vyvanse:Adderall). For 30 mg total daily Adderall, this translates to 45-60 mg of Vyvanse 1.
Dosing Algorithm
Initial conversion:
- Start at 50 mg Vyvanse once daily (middle of the 45-60 mg range)
- Take in the morning after waking
Titration schedule if needed:
- Assess response after 1 week
- If inadequate symptom control: increase by 10 mg weekly increments up to maximum 70 mg daily 1, 2
- If side effects are problematic: decrease to 40 mg daily
Important Clinical Considerations
Duration of action differences:
- Vyvanse provides approximately 12-14 hours of coverage 2, 3
- The patient's current regimen (Adderall XR + IR) likely provides split coverage throughout the day
- The IR dose may have been used for afternoon/evening symptom control - assess if single daily Vyvanse dosing provides adequate all-day coverage
Common pitfalls to avoid:
- Do not simply add the milligram amounts (20 + 10 = 30 mg Vyvanse would be underdosing)
- Monitor for appetite suppression and insomnia - these may be more pronounced with Vyvanse's longer duration 2
- Check blood pressure and heart rate at follow-up visits 1
Monitoring parameters:
- Assess ADHD symptom control at 1 week and 2-4 weeks post-conversion
- Monitor weight, blood pressure, and pulse
- Evaluate sleep quality and appetite
- Ask specifically about symptom coverage in late afternoon/evening hours
If conversion is inadequate:
- Consider that the patient may need the higher end of the conversion range (60 mg)
- Some patients may require addition of a small afternoon IR dose if evening coverage is insufficient with once-daily Vyvanse
- Maximum FDA-approved dose is 70 mg daily 2