Equivalent Dose Conversion from Concerta 18mg to Vyvanse
For a patient taking Concerta 18mg, the equivalent Vyvanse dose is approximately 30mg, based on the amphetamine-to-methylphenidate conversion ratio of 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
Concerta 18mg delivers methylphenidate coverage equivalent to approximately 6mg of immediate-release methylphenidate given three times daily (total 18mg daily). 2
Vyvanse 30mg converts to approximately 8.9mg of active dextroamphetamine after metabolism, which provides therapeutic equivalence to Concerta 36mg (double the 18mg dose). 1
Working backward from this established conversion, Concerta 18mg (half of 36mg) corresponds to approximately Vyvanse 20-30mg. 1
Practical Switching Protocol
Start with Vyvanse 30mg when transitioning from Concerta 18mg, as this represents the closest available dose strength. 1
No washout period is required when switching between stimulant classes, as both medications have short half-lives and can be transitioned directly. 1
Assess response after 1 week at the initial 30mg dose before making any adjustments. 1
If symptom control is inadequate after 1 week, consider increasing to Vyvanse 40mg. 1
Allow at least 4 weeks at a therapeutic dose before determining treatment failure. 1
Important Pharmacokinetic Differences
Concerta 18mg provides coverage for approximately 12 hours using its OROS delivery system, with an ascending release profile throughout the day. 2, 3
Vyvanse provides coverage for approximately 13-14 hours as a prodrug that requires enzymatic conversion to active dextroamphetamine. 4
The different release mechanisms mean that even at equivalent doses, patients may experience different timing of peak effects and duration of coverage. 5
Monitoring Considerations
Cardiovascular monitoring should continue as with any stimulant therapy, including pulse and blood pressure assessment. 4, 1
Monitor for nausea during the first week, which occurs in up to 25% of patients starting amphetamine-based medications. 1
Watch for differences in appetite suppression and sleep disturbances, as amphetamine products may produce more pronounced effects on these parameters compared to methylphenidate. 4
Height and weight monitoring should continue, as both medication classes are associated with reductions in growth velocity. 4
Common Pitfall to Avoid
Do not assume 1:1 dose equivalence between Concerta and Vyvanse milligram amounts. The conversion requires accounting for the different potencies of methylphenidate versus amphetamine compounds. 1
Be aware that generic non-OROS methylphenidate formulations may not provide equivalent therapeutic effects to brand-name Concerta, which could complicate conversion calculations if the patient was previously on a generic formulation. 6