Adderall Equivalent Dosing to Lisdexamfetamine 70 mg
The equivalent dose of Adderall (mixed amphetamine salts) for a patient taking lisdexamfetamine 70 mg is approximately 30-40 mg total daily dose, based on equimolar conversion and clinical trial data. 1, 2
Pharmacokinetic Basis for Conversion
Lisdexamfetamine is a prodrug that is enzymatically converted to dextroamphetamine after oral ingestion, with the l-lysine amino acid cleaved off through rate-limited hydrolysis in the blood. 3, 4
On an equimolar basis, 100 mg of lisdexamfetamine delivers the same total amphetamine exposure (AUC) as 40 mg of immediate-release d-amphetamine, though with a delayed time to peak concentration by approximately 1 hour. 5
Using this equimolar ratio, 70 mg of lisdexamfetamine would be equivalent to approximately 28 mg of pure d-amphetamine. 5
Clinical Trial-Based Conversion
In a direct comparison crossover study, lisdexamfetamine up to 70 mg daily was compared with mixed amphetamine salts immediate-release up to 45 mg daily (divided three times daily), with both producing significant and generally equal reductions in ADHD symptoms. 1
In a pediatric analog classroom study, lisdexamfetamine 70 mg was compared with mixed amphetamine salts extended-release 30 mg, with both active treatments showing similar efficacy profiles. 2
Practical Dosing Recommendation
Start with Adderall XR 30 mg once daily in the morning as the initial equivalent dose when converting from lisdexamfetamine 70 mg. 3, 6
If using immediate-release Adderall, begin with 10-15 mg twice daily (20-30 mg total daily dose) and titrate upward in 5 mg increments weekly based on response, with a potential range up to 40 mg total daily dose. 3, 1
The maximum recommended total daily dose for Adderall is 50 mg for adults, though clinical practice sometimes uses up to 40 mg as a practical upper limit when given in multiple doses throughout the day. 3, 6
Important Caveats
Lisdexamfetamine has a longer duration of action (13-14 hours) compared to Adderall XR (approximately 10-12 hours), so patients may experience earlier symptom return in the evening after conversion. 7
The pharmacokinetic profile of lisdexamfetamine produces lower peak concentrations and more gradual onset compared to equivalent doses of amphetamine salts, which may result in differences in subjective effects and tolerability. 5, 7
Monitor closely for breakthrough symptoms in the late afternoon/evening and for side effects including insomnia, decreased appetite, increased blood pressure and heart rate during the conversion period. 3
Titrate the final Adderall dose based on clinical response rather than strict mathematical conversion, as individual patient factors affect optimal dosing. 3, 1