Dose Conversion from Ritalin LA 20mg to Vyvanse
When switching from Ritalin LA (methylphenidate) 20mg to Vyvanse (lisdexamfetamine), start with Vyvanse 30mg based on the established amphetamine to methylphenidate conversion ratio of approximately 1:1.2 to 1:2. 1
Conversion Rationale
- The American Academy of Child and Adolescent Psychiatry recommends an amphetamine to methylphenidate conversion ratio of approximately 1:1.2 to 1:2 to achieve equivalent therapeutic effect 1
- Vyvanse 30mg converts to approximately 8.9mg of active dextroamphetamine after enzymatic hydrolysis in the blood 1, 2
- This dose provides comparable ADHD symptom control to methylphenidate formulations in the 20-24mg range 1
Immediate Transition Protocol
- No washout period is required when switching between stimulant classes, as both medications have short half-lives and can be transitioned directly 1
- Discontinue Ritalin LA and start Vyvanse 30mg the following morning 1
Monitoring and Titration Strategy
- Assess response after 1 week at the initial 30mg dose before making any adjustments 1
- If symptom control is inadequate after 1 week, increase to Vyvanse 50mg 1
- Allow at least 4 weeks at a therapeutic dose before determining treatment failure 1
- Lisdexamfetamine demonstrates efficacy from 1.5 hours postdose through 13 hours in school-aged children, providing longer duration than immediate-release formulations 3
Duration of Effect Considerations
- Vyvanse provides extended coverage with efficacy demonstrated at 14 hours postdose in adults, which may be advantageous if Ritalin LA's 8-hour duration was insufficient 4
- Behavioral and cognitive benefits peak at approximately 2 hours postdose with methylphenidate formulations, whereas lisdexamfetamine maintains more consistent effects throughout the day 5, 3
Common Pitfalls and Monitoring
- Monitor for decreased appetite (47% during dose optimization), insomnia (27%), headache (17%), and irritability (16%) during the first week, though these adverse events typically decrease in frequency after initial titration 3
- If insomnia occurs, ensure morning dosing and avoid late administration 6
- The most common treatment-emergent adverse events are typically mild to moderate in intensity and rarely lead to discontinuation 3, 7
Special Considerations
- Lisdexamfetamine is a prodrug that requires enzymatic conversion in red blood cells to become active, providing a smoother pharmacokinetic profile compared to immediate-release formulations 2, 4
- Once-daily dosing eliminates the need for in-school medication administration, improving adherence and reducing peer stigma 8, 5
- Cardiovascular monitoring should continue as with any stimulant therapy 1