What is the equivalent dose of mixed amphetamine salts extended-release (Adderall XR) to lisdexamfetamine (Vyvanse) 70 mg?

Equivalent Dose of Adderall XR to Vyvanse 70 mg

Vyvanse 70 mg is approximately equivalent to Adderall XR 30 mg based on the active amphetamine content delivered after prodrug conversion. 1

Pharmacological Basis for Conversion

Active Drug Content After Metabolism

• Vyvanse 70 mg contains 70 mg of lisdexamfetamine dimesylate, which is equivalent to 40.5 mg of lisdexamfetamine base. 1
• Lisdexamfetamine is a prodrug that is converted to dextroamphetamine through hydrolysis by red blood cells after oral administration. 1
• The conversion is not metabolized by cytochrome P450 enzymes but occurs primarily in blood due to red blood cell hydrolytic activity. 1
• After conversion, Vyvanse 70 mg delivers approximately 28–30 mg of active dextroamphetamine systemically. 1, 2

Adderall XR Composition

• Adderall XR contains a 50:50 mixture of dextroamphetamine and levoamphetamine salts. 3, 4
• Adderall XR 30 mg therefore delivers approximately 15 mg of dextroamphetamine plus 15 mg of levoamphetamine. 3, 4
• Because dextroamphetamine is approximately twice as potent as levoamphetamine at dopamine and norepinephrine transporters, the effective dextroamphetamine-equivalent dose of Adderall XR 30 mg is roughly 22–25 mg. 3, 4

Clinical Equivalence in Practice

Direct Comparison Study

• A randomized, double-blind crossover study in children with ADHD directly compared lisdexamfetamine (30,50,70 mg) with mixed amphetamine salts extended-release (10,20,30 mg) and found similar efficacy profiles when Vyvanse 70 mg was compared to MAS-XR 30 mg. 5
• Both medications significantly improved ADHD symptoms versus placebo, with adverse event profiles that were similar between the two active treatments. 5

Guideline-Based Dosing Ranges

• The FDA-approved maximum dose for both medications is 70 mg/day for Vyvanse and 40 mg/day for Adderall XR. 6, 1
• Clinical practice guidelines recommend starting Adderall XR at 5 mg once or twice daily in adults and titrating by 5–10 mg weekly to a typical therapeutic range of 20–40 mg/day. 3, 4
• For Vyvanse, guidelines recommend starting at 30 mg every morning and titrating by 10–20 mg weekly to a therapeutic range of 30–70 mg/day. 1

Practical Conversion Algorithm

When Switching from Vyvanse 70 mg to Adderall XR

1. Start Adderall XR at 30 mg once daily in the morning. 3, 4
2. Monitor response over 1 week using standardized ADHD rating scales from the patient or significant others. 3, 4
3. If symptom control is inadequate, increase to 40 mg/day (the FDA maximum). 6
4. If 40 mg is insufficient, consider switching back to Vyvanse or adding psychosocial interventions rather than exceeding the dose ceiling. 6

When Switching from Adderall XR to Vyvanse

1. Start Vyvanse at 50–70 mg once daily in the morning if the patient was stable on Adderall XR 30 mg. 1
2. Monitor for 1 week and adjust by 10–20 mg increments if needed. 1
3. The maximum dose of 70 mg/day should not be exceeded. 1

Important Clinical Caveats

Pharmacokinetic Differences

• Vyvanse has a longer duration of action (approximately 13 hours) compared to Adderall XR (approximately 10–12 hours) due to the prodrug conversion mechanism. 1
• Peak plasma concentrations of dextroamphetamine occur at 3.5–4 hours after Vyvanse administration versus 2–3 hours after Adderall XR. 1
• This difference means that Vyvanse may provide more consistent afternoon coverage but may also increase the risk of evening insomnia. 7, 3

Side Effect Profile Considerations

• Amphetamines (including both medications) are associated with greater appetite suppression and sleep disturbances compared to methylphenidate due to their longer half-lives. 3, 4
• Vyvanse's prodrug mechanism may reduce abuse potential compared to immediate-release amphetamines, but both medications carry a high risk for abuse, misuse, and addiction. 1
• Monitor blood pressure and pulse quarterly in adults and annually in children receiving either medication. 3, 4, 6

Renal Impairment Adjustments

• In patients with severe renal impairment, the maximum Vyvanse dose is 50 mg/day. 1
• In patients with end-stage renal disease, the maximum Vyvanse dose is 30 mg/day. 1
• No specific renal dose adjustments are provided in guidelines for Adderall XR, but caution is warranted. 3, 4

Common Pitfall to Avoid

• Do not assume a 1:1 mg-for-mg conversion between Vyvanse and Adderall XR; the prodrug mechanism and mixed amphetamine composition make direct milligram equivalence misleading. 1, 5
• Do not exceed FDA-approved maximum doses (70 mg Vyvanse, 40 mg Adderall XR) even if lower doses are ineffective; instead, switch medication classes or augment with behavioral interventions. 6, 1