What is the appropriate dosage of mixed amphetamine salts extended‑release (Adderall XR) when switching a patient from 60 mg lisdexamfetamine (Vyvanse)?

Switching from 60mg Vyvanse to Adderall XR: Recommended Dosage

When switching from 60 mg Vyvanse (lisdexamfetamine) to Adderall XR, start with 30 mg Adderall XR once daily in the morning, then titrate by 5-10 mg weekly based on symptom control and tolerability.

Rationale for Conversion

The conversion is not straightforward because lisdexamfetamine is a prodrug that requires enzymatic conversion to active d-amphetamine, while Adderall XR contains mixed amphetamine salts (75% dextroamphetamine and 25% levoamphetamine) that are immediately active. The pharmacokinetic profiles differ significantly 1.

Starting Dose Recommendation

• Initial dose: 30 mg Adderall XR once daily 2
• This represents a conservative conversion that accounts for the different pharmacokinetic profiles
• The FDA label for Adderall XR specifies that adults switching from another medication should start at either 10 mg or 20 mg daily, but given the patient is on a high dose of Vyvanse (60 mg), starting at 30 mg is more appropriate to avoid symptom breakthrough 2

Titration Strategy

Increase by 5-10 mg weekly until optimal symptom control is achieved 3, 2:

• Week 1: 30 mg once daily
• Week 2: 35-40 mg once daily (if needed)
• Week 3: 40-50 mg once daily (if needed)
• Maximum dose: 50 mg daily (though FDA label states doses can go higher, the maximum recommended is typically 50 mg) 4

Important Clinical Considerations

Why Not a Direct 1:1 Conversion?

Lisdexamfetamine 60 mg does not convert directly to 60 mg Adderall XR because:

• Lisdexamfetamine is a prodrug requiring red blood cell enzymatic conversion to d-amphetamine 5, 1
• Only the d-amphetamine component becomes active after hydrolysis
• Adderall XR contains both d- and l-amphetamine isomers in immediate bioavailable form
• The pharmacokinetic profiles differ: lisdexamfetamine has delayed onset but longer duration 6, 5

Monitoring During Transition

Assess weekly during titration 3:

• Blood pressure and pulse at each visit
• ADHD symptom rating scales (from patient and significant other if available)
• Side effects: appetite suppression, insomnia, irritability, cardiovascular symptoms
• Weight monitoring

Common Pitfalls to Avoid

1. Starting too low: Beginning at 10 mg when the patient is on 60 mg Vyvanse will likely result in significant symptom breakthrough and treatment dissatisfaction
2. Switching abruptly without overlap: Consider a brief overlap period if symptoms are severe
3. Not accounting for duration differences: Adderall XR may have shorter duration than Vyvanse; some patients may need afternoon supplementation with immediate-release amphetamine (5-10 mg) 3
4. Ignoring cardiovascular monitoring: Both medications increase blood pressure and heart rate; monitor at each dose adjustment 2

Maximum Dosing

While the FDA label states the maximum studied dose for Adderall XR is 50 mg daily in adults 2, clinical practice guidelines note that doses may occasionally exceed this in treatment-refractory cases 3. However, recent meta-analysis data suggests that unlicensed (higher) doses may not provide substantial additional benefit and increase adverse event risk 7.

Alternative Approach

If 30 mg seems too aggressive as a starting dose, you could:

• Start at 20 mg Adderall XR daily
• Increase by 10 mg weekly
• This would reach therapeutic equivalence more gradually but risks a longer period of suboptimal symptom control

The key principle is flexible titration based on clinical response and tolerability, not rigid dose equivalence tables 8.