Switching from Vyvanse 80 mg to Adderall in Pediatric ADHD
Start Adderall XR at 30 mg once daily in the morning, which represents approximately 50% of the lisdexamfetamine dose, then titrate by 5-10 mg weekly based on response up to a maximum of 50 mg daily. 1
Conversion Rationale
The conversion from Vyvanse (lisdexamfetamine) to Adderall requires dose reduction because lisdexamfetamine is a prodrug that must be enzymatically converted to dextroamphetamine, resulting in different pharmacokinetics. 2, 3
- Lisdexamfetamine undergoes rate-limited hydrolysis in the body, gradually releasing active d-amphetamine through enzymatic cleavage of the l-lysine molecule 3, 4
- This prodrug mechanism creates a more gradual release profile compared to direct amphetamine formulations 2
- A conservative starting conversion ratio of approximately 1.5:1 to 2:1 (Vyvanse:Adderall) is clinically prudent, meaning 80 mg Vyvanse converts to approximately 30-40 mg Adderall XR 1
Specific Dosing Protocol
Begin with Adderall XR 30 mg once daily in the morning to minimize sleep disturbances. 1, 5
- Titrate by 5-10 mg weekly increments based on symptom control using standardized ADHD rating scales 1, 5
- The maximum recommended daily dose is 50 mg for both Adderall XR and IR formulations 1
- For children weighing less than 25 kg, single doses should generally not exceed 15 mg 1
Alternative Immediate-Release Option
If switching to Adderall IR instead of XR:
- Start with 10 mg twice daily (morning and early afternoon) 1
- Titrate by 5 mg increments weekly 1
- Maximum total daily dose remains 50 mg 1
- IR formulations require 2-3 times daily dosing with effects lasting 4-6 hours 6
Monitoring Requirements
Assess blood pressure and pulse at baseline and with each dose increase, particularly given the higher starting dose from the Vyvanse conversion. 5
- Evaluate therapeutic effects using standardized ADHD rating scales (such as ADHD-RS-IV) at each follow-up 2, 7
- Monitor for common adverse effects including decreased appetite, insomnia, upper abdominal pain, headache, and irritability 2, 8
- Schedule follow-up appointments at least monthly until symptoms are stabilized 5
- Assess for any changes in side effect profile, as altered absorption kinetics between the two medications may affect tolerability 1
Critical Pitfalls to Avoid
Do not use a 1:1 dose conversion, as this would result in excessive amphetamine exposure and increased risk of cardiovascular and neuropsychiatric adverse effects. 1, 8
- Avoid starting at too high a dose, which can lead to unnecessary side effects and decreased medication adherence 5
- Do not increase doses more frequently than weekly, as insufficient time between increases prevents adequate assessment of response 5
- Never exceed the 50 mg maximum daily dose; if inadequate response occurs at maximum dosing, switch to an alternative stimulant or add a non-stimulant medication rather than exceeding recommended limits 1, 5
- Ensure morning administration for extended-release formulations to minimize sleep disturbances 1, 5
Special Considerations for Adolescents
Before switching medications in adolescents, assess for symptoms of substance abuse and monitor for signs of medication diversion. 9
- Adolescents have particular concerns regarding diversion of ADHD medications 9
- The original choice of Vyvanse may have been intentional due to its lower abuse potential compared to immediate-release amphetamines 9, 2
- Consider whether the switch to Adderall is clinically necessary or if optimizing the current Vyvanse regimen might be preferable 9
- Monitor prescription refill requests for signs of misuse or diversion 9
If Maximum Dose Proves Inadequate
Switch to an alternative stimulant (such as methylphenidate-based products) or add a non-stimulant medication like atomoxetine, guanfacine, or clonidine rather than exceeding the 50 mg Adderall maximum. 9, 1, 5