What is the recommended conversion dose from Adderall (amphetamine and dextroamphetamine) 15mg twice daily (bid) to Vyvanse (lisdexamfetamine) for an adult or adolescent patient with Attention Deficit Hyperactivity Disorder (ADHD) and potential cardiovascular issues or history of substance abuse?

Adderall 15mg BID to Vyvanse Conversion

Direct Conversion Recommendation

Convert Adderall 15mg twice daily (total 30mg/day) to Vyvanse 70mg once daily in the morning. 1

The conversion follows an approximate 2.5:1 ratio (Vyvanse:Adderall), which translates your total daily Adderall dose of 30mg to approximately 75mg of Vyvanse, but since the maximum FDA-approved dose is 70mg daily, start at this ceiling dose. 1

Conversion Algorithm

Step 1: Calculate Total Daily Amphetamine Dose

• Your current regimen: 15mg BID = 30mg total daily amphetamine salts 2
• This is within the typical adult therapeutic range of 10-50mg daily for mixed amphetamine salts 3

Step 2: Apply Conversion Factor

• Using the 2.5:1 conversion ratio: 30mg Adderall × 2.5 = 75mg Vyvanse 1
• Since maximum Vyvanse dose is 70mg daily, initiate at 70mg once daily 1, 4

Step 3: Discontinuation and Initiation

• Discontinue Adderall abruptly without tapering when switching to Vyvanse, as no washout period is required between stimulant medications 5
• Start Vyvanse 70mg the morning after your last Adderall dose 5

Special Considerations for Your Clinical Context

Cardiovascular Monitoring

• Both methylphenidate and dextroamphetamine (including lisdexamfetamine) should be avoided in patients with uncontrolled hypertension, underlying coronary artery disease, and tachyarrhythmias 2
• Monitor blood pressure and pulse at baseline and regularly during treatment 3
• Rare but serious cardiovascular side effects include hypertension, palpitations, and arrhythmias 2

Substance Abuse History Considerations

• Lisdexamfetamine (Vyvanse) is specifically advantageous for patients with substance abuse concerns due to its prodrug formulation, which requires enzymatic conversion to active d-amphetamine in the blood, conferring lower abuse potential compared to immediate-release formulations 6, 4, 7
• Long-acting formulations like Vyvanse have lower abuse potential and are resistant to diversion compared to immediate-release stimulants 3
• Case reports demonstrate successful treatment of ADHD with lisdexamfetamine in patients with active stimulant (methamphetamine) use disorder, with decreased cravings for illicit stimulants 6

Expected Timeline and Monitoring

Immediate Effects

• Expect therapeutic effects within hours of the first Vyvanse dose, as stimulants work rapidly unlike non-stimulants which require weeks for full benefit 5, 3
• Peak plasma concentrations of d-amphetamine from lisdexamfetamine occur approximately 1 hour later than immediate-release amphetamine, with a lag time of 0.6 hours longer 8

Duration of Action

• Vyvanse provides full-day coverage (up to 13-14 hours) with once-daily dosing, eliminating the need for afternoon doses and improving medication adherence 4, 9
• This extended duration addresses the common "wearing-off" effect seen with twice-daily immediate-release formulations 3

Dose Adjustments

• If 70mg provides inadequate symptom control after 1 week, do not exceed the maximum dose of 70mg daily 1, 4
• If response is inadequate at maximum dose, consider switching to methylphenidate class rather than exceeding recommended amphetamine doses 3
• Dosage adjustments can be made in 10mg increments at weekly intervals if starting below 70mg 1

Common Pitfalls to Avoid

• Do not use weight-adjusted dosing for this conversion, as current research does not uniformly support titrating with weight-adjusted doses and this method is problematic in practice 2
• Do not assume you need a lower starting dose simply because you're switching formulations—your current 30mg total daily dose supports initiating at the higher end of the Vyvanse range 1
• Do not combine Vyvanse with MAO inhibitors due to risk of severe hypertension and potential cerebrovascular accidents; ensure at least 14 days have elapsed if patient was on an MAOI 3
• Do not split or crush Vyvanse capsules for dose adjustment—the capsule can be opened and contents mixed with water for administration, but the prodrug mechanism requires intact lisdexamfetamine for proper conversion 4

Monitoring Parameters

• Blood pressure and heart rate at each visit 3
• Weight and appetite changes, as decreased appetite is a common adverse effect 4, 9
• Sleep quality and timing, adjusting administration time if insomnia occurs 2, 4
• ADHD symptom response using standardized rating scales within the first week 2, 3
• In patients with substance abuse history: monthly urine drug screens and assessment for cravings or relapse 3, 6