What is the equivalent dose of Vyvanse (lisdexamfetamine) for a patient taking Adderall (amphetamine and dextroamphetamine) 15mg three times a day (TID)?

Adderall 15mg TID to Vyvanse Conversion

For a patient taking Adderall 15mg three times daily (total daily dose 45mg), convert to Vyvanse 70mg once daily in the morning. 1

Conversion Calculation

• Total daily Adderall dose: 15mg × 3 = 45mg per day
• Conversion ratio: Apply approximately 2.5:1 (Vyvanse:Adderall) when switching between these amphetamine formulations 1
• Calculated Vyvanse equivalent: 45mg × 2.5 = 112.5mg
• Practical dose: Since the maximum FDA-approved dose of Vyvanse is 70mg daily, start at 70mg once daily in the morning 1, 2

Rationale for Maximum Dose

• Vyvanse is dosed once daily with a maximum of 70mg, and can be adjusted in 10mg increments at weekly intervals if needed 1, 3
• The 70mg dose represents the ceiling for this medication regardless of prior stimulant exposure 2, 4
• Lisdexamfetamine (Vyvanse) is a prodrug that is enzymatically hydrolyzed primarily in red blood cells to active d-amphetamine, providing extended duration of effect up to 14 hours in adults 2, 3

Switching Protocol

• Discontinue Adderall immediately without tapering when switching to Vyvanse, as no washout period is required between amphetamine formulations 5
• Initiate Vyvanse 70mg the following morning as a single daily dose 1, 3
• Timing: Administer in the morning to minimize sleep disturbances 6

Monitoring After Conversion

• Vital signs: Check blood pressure and pulse at baseline and with each follow-up, as stimulants can increase both parameters 6, 5
• Efficacy assessment: Use standardized ADHD rating scales to evaluate symptom control at weekly intervals initially 6
• Follow-up schedule: Monthly appointments until symptoms are stabilized, then at least every 3 months 6
• Duration of effect: Vyvanse provides efficacy for 14 hours post-dose in adults, which may better cover late-day symptoms compared to multiple daily Adderall doses 2, 3

Common Pitfalls to Avoid

• Do not attempt to exceed 70mg Vyvanse even though the mathematical conversion suggests a higher dose—70mg is the regulatory maximum 1, 2
• Do not split the Vyvanse dose into multiple daily administrations; it is designed as once-daily therapy 3, 4
• Do not overlook cardiovascular monitoring, particularly in patients with pre-existing hypertension or cardiac conditions 6
• Avoid evening dosing as the extended duration of Vyvanse (up to 14 hours) will cause insomnia 2, 3

Expected Adverse Effects

• Most common side effects include decreased appetite, insomnia, headache, irritability, and nausea—consistent with amphetamine products generally 3, 4
• These effects are typically mild to moderate in intensity and transient 4
• The tolerability profile of Vyvanse is consistent with other long-acting stimulants 2, 3

If Inadequate Response at 70mg

• Reassess diagnosis and evaluate for comorbid conditions affecting treatment response (sleep disorders, anxiety, depression) 6
• Consider alternative stimulant formulations or adding a non-stimulant medication like atomoxetine 6
• Evaluate adherence and timing of administration to ensure optimal therapeutic effect 6