What dosage of Adderall (amphetamine and dextroamphetamine) should be prescribed to an adult patient with Attention Deficit Hyperactivity Disorder (ADHD) who is currently stable on Vyvanse (lisdexamfetamine) 40mg, but needs to switch due to insurance coverage issues?

Switching from Vyvanse 40mg to Adderall: Dosing Recommendation

Start with Adderall XR 20mg once daily in the morning, which represents an approximately equivalent therapeutic dose to Vyvanse 40mg. 1

Conversion Rationale

• Vyvanse (lisdexamfetamine) is a prodrug that is enzymatically converted to d-amphetamine in the body after oral administration 2, 3
• Vyvanse 40mg delivers approximately 12-13mg of active d-amphetamine once fully metabolized 4
• Adderall contains a 3:1 ratio of d-amphetamine to l-amphetamine salts, so the total amphetamine content is higher than pure d-amphetamine equivalents 5
• A reasonable starting conversion is Adderall XR 20mg for Vyvanse 40mg, which provides comparable therapeutic coverage while accounting for the mixed amphetamine salts formulation 1

Titration Strategy if Initial Dose is Inadequate

• Allow at least one week at the initial 20mg dose to properly evaluate therapeutic response and side effects before making any adjustments 1
• If symptom control is insufficient after one week, increase by 5-10mg increments weekly based on clinical response 5, 1
• The maximum recommended daily dose of Adderall XR is 40-50mg for adults 1
• Assess both therapeutic effects (attention, focus, organization) and side effects (appetite, sleep, cardiovascular symptoms) before each dose increase 1

Administration and Monitoring

• Administer Adderall XR in the morning to minimize sleep disturbances 1
• Monitor blood pressure and pulse at baseline and with each dose change, as stimulants can cause cardiovascular effects 1
• Weigh the patient at each visit to monitor for appetite suppression 1
• The once-daily XR formulation improves adherence by eliminating the need for multiple daily doses 1

Common Pitfalls to Avoid

• Do not start at too high a dose (such as 30mg), which can lead to unnecessary side effects and decreased adherence 1
• Do not increase the dose before allowing at least one week to evaluate response 1
• Do not continue increasing beyond the maximum recommended dose (40-50mg) if ineffective—instead, consider switching to methylphenidate-based stimulants or non-stimulant options 6, 1
• Do not overlook morning administration timing, as afternoon or evening dosing significantly increases insomnia risk 1