What is the equivalent dose of Vyvanse (lisdexamfetamine) for a patient taking Adderall (amphetamine and dextroamphetamine) 25mg Extended Release (XR)?

Adderall XR 25mg to Vyvanse Conversion

The equivalent dose of Vyvanse (lisdexamfetamine) for a patient taking Adderall XR 25mg would be approximately 50-60mg. 1

Pharmacological Basis for Conversion

Adderall XR and Vyvanse have different mechanisms of drug delivery and pharmacokinetic profiles:

• Adderall XR (mixed amphetamine salts): Contains immediate and delayed-release beads of mixed amphetamine salts that provide approximately 12 hours of coverage 2
• Vyvanse (lisdexamfetamine): A prodrug that requires enzymatic conversion in the bloodstream to active d-amphetamine, providing consistent drug delivery over approximately 14 hours 3

Key Conversion Considerations:

1. Bioavailability differences:

   • Vyvanse is converted to d-amphetamine primarily by red blood cells 4
   • This conversion process results in more consistent drug delivery compared to Adderall XR, which can be affected by food intake 5

2. Potency ratio:

   • The American Academy of Child and Adolescent Psychiatry guidelines suggest that when converting between amphetamine formulations, the equivalent dose of Vyvanse is approximately twice the dose of Adderall XR 1
   • This is because Vyvanse contains only d-amphetamine (after conversion), while Adderall contains a mixture of d-amphetamine and l-amphetamine salts

Dosing Algorithm

For converting from Adderall XR 25mg to Vyvanse:

1. Initial conversion calculation:

   • Multiply Adderall XR dose by approximately 2-2.5
   • For 25mg Adderall XR: 25mg × 2 to 2.5 = 50-62.5mg Vyvanse

2. Practical dosing:

   • Vyvanse is available in 10,20,30,40,50,60, and 70mg capsules
   • Therefore, the most appropriate dose would be 50mg or 60mg

3. Titration considerations:

   • Start with 50mg if the patient is sensitive to medication side effects
   • Consider 60mg if optimal symptom control is the priority

Monitoring After Conversion

After switching from Adderall XR to Vyvanse, monitor:

• Efficacy: Assess symptom control throughout the day, particularly in the afternoon when Adderall XR may begin to wear off

• Side effects: Monitor for common stimulant side effects including:

  • Decreased appetite
  • Sleep disturbances
  • Increased blood pressure/heart rate
  • Headaches
  • Irritability 1

• Timing considerations: Unlike Adderall XR, Vyvanse's absorption is less affected by food intake, which may provide more consistent symptom control 5

Important Clinical Considerations

• Duration of action: Vyvanse may provide longer symptom control (up to 14 hours) compared to Adderall XR (approximately 12 hours) 3
• Abuse potential: While both medications are Schedule II controlled substances, Vyvanse's prodrug mechanism may provide some theoretical reduction in abuse potential when compared to immediate-release formulations, though this benefit is less clear when comparing to Adderall XR 6, 7
• Consistency: Vyvanse provides more consistent drug delivery that is less affected by food intake compared to Adderall XR 5

Remember that individual response to stimulant medications varies, and close follow-up after medication conversion is essential to ensure optimal symptom control and minimize side effects.