Vyvanse Dose Conversion from Adderall 25 mg
When switching from Adderall 25 mg daily to Vyvanse, start with Vyvanse 50 mg daily.
Conversion Rationale
The conversion is based on amphetamine base equivalence and clinical pharmacology. Adderall 25 mg contains approximately 15.6 mg of amphetamine base 1. Since Vyvanse (lisdexamfetamine) is a prodrug that converts to dextroamphetamine after oral administration 2, and considering that lisdexamfetamine 70 mg provides therapeutic effects comparable to mixed amphetamine salts, a 2:1 conversion ratio is appropriate.
The practical conversion approach:
- Adderall 25 mg → Vyvanse 50 mg as the starting dose
- May titrate to Vyvanse 60-70 mg if needed for optimal symptom control
Clinical Evidence Supporting This Conversion
A crossover study directly comparing lisdexamfetamine (up to 70 mg/day) with mixed amphetamine salts immediate-release (up to 45 mg/day) found equivalent efficacy on ADHD rating scales, with response rates of approximately 80% for both medications 3. This suggests that higher doses of Vyvanse are needed to achieve similar clinical effects as lower doses of Adderall.
Key pharmacokinetic differences to consider:
- Vyvanse has a longer duration of action (10-13 hours) compared to immediate-release Adderall (4-6 hours)
- Vyvanse reaches peak dextroamphetamine levels at approximately 3.5-4 hours post-dose 2
- The prodrug mechanism provides more gradual onset and offset of effects
Titration Strategy After Conversion
Following the switch to Vyvanse 50 mg:
- Week 1-2: Assess response on Vyvanse 50 mg daily
- If inadequate response: Increase by 10-20 mg weekly increments 4
- Maximum dose: 70 mg daily (FDA-approved maximum) 4
- Monitor: Blood pressure, pulse, appetite, sleep, and ADHD symptom control at each adjustment
The 2024 AJOG guidelines specify that Vyvanse should be started at 20-30 mg with titration by 10 mg weekly up to a maximum of 70 mg daily 4. However, when converting from an established Adderall dose, starting at 50 mg is appropriate to maintain therapeutic coverage.
Important Clinical Considerations
Common pitfalls to avoid:
- Do not use a 1:1 mg-to-mg conversion—this will result in underdosing
- Do not split Vyvanse doses throughout the day—it is designed for once-daily morning administration
- Do not assume immediate equivalence; some patients may need the full 70 mg to match their previous Adderall response
Monitoring requirements:
- Check blood pressure and pulse at baseline and with each dose adjustment 5
- Assess for appetite suppression and weight loss (more pronounced with amphetamines than methylphenidate) 5
- Evaluate sleep onset—Vyvanse's longer duration may affect evening sleep more than immediate-release Adderall
If the patient was taking Adderall XR (extended-release) 25 mg: The same conversion to Vyvanse 50 mg applies, as both are long-acting formulations.
Recent dose-effect network meta-analysis data suggest that amphetamines show increasing efficacy up to approximately 25 mg/day in children and 50 mg/day in adults, with plateaus above these doses 6. This supports starting at Vyvanse 50 mg (which delivers approximately 29 mg dextroamphetamine base) when converting from Adderall 25 mg.