From the Guidelines
The equivalent dose of Vyvanse (lisdexamfetamine) for a patient taking 20 mg of dextroamphetamine sulfate daily is approximately 30-40 mg of Vyvanse, considering the usual starting dose and titration schedule. When converting between these medications, it's essential to understand that Vyvanse is a prodrug that is metabolized in the body to release dextroamphetamine, as noted in the study by Scoten et al. 1. The study provides information on the usual starting dose and titration schedule for Vyvanse, which can be used as a guide for conversion.
- Key points to consider when converting between dextroamphetamine and Vyvanse include:
- The pharmacokinetic profile of Vyvanse, which typically provides a smoother, more gradual onset and longer duration of action compared to immediate-release dextroamphetamine.
- The need for individualized dosing and monitoring, as patients may respond differently to the conversion.
- The importance of medical supervision during the conversion process, with adjustments made based on clinical response, as suggested by the study 1. It's crucial to prioritize the patient's response and adjust the dosage accordingly, rather than relying solely on a standard conversion ratio, to minimize potential adverse effects and optimize treatment outcomes, in line with the principles of minimizing morbidity, mortality, and improving quality of life.
From the Research
Equivalent Dose of Vyvanse for Dextroamphetamine Sulfate
To determine an equivalent dose of Vyvanse (lisdexamfetamine) for a patient taking dextroamphetamine sulfate 20 mg daily, we need to consider the pharmacological profiles of both medications.
- Lisdexamfetamine is a prodrug that is converted into d-amphetamine in the body, which then acts as a stimulant 2.
- The conversion rate and the resulting pharmacological effects can influence the equivalent dose.
Pharmacological Comparison
Studies comparing lisdexamfetamine with other ADHD medications provide insights into their relative potencies and effects:
- A systematic evidence synthesis comparing treatments for ADHD in children and adolescents found that lisdexamfetamine had a better response profile compared to methylphenidate and atomoxetine 3.
- A study using dual-probe microdialysis in rats showed that lisdexamfetamine had larger and more sustained effects on catecholaminergic neurotransmission compared to methylphenidate and modafinil 4.
Dosing Considerations
Given that lisdexamfetamine is converted into d-amphetamine, the dosing should consider the amount of d-amphetamine produced:
- The typical starting dose of Vyvanse is 30 mg once daily, with increments up to 70 mg/day 3.
- For dextroamphetamine sulfate, the typical dose range is 5-40 mg/day, given in divided doses 5.
Equivalent Dose Estimation
Based on the pharmacological profiles and considering the conversion of lisdexamfetamine to d-amphetamine:
- A dose of 20 mg dextroamphetamine sulfate daily might be roughly equivalent to a dose of Vyvanse that produces a similar amount of d-amphetamine.
- However, due to the lack of direct comparison studies between dextroamphetamine sulfate and Vyvanse, the exact equivalent dose cannot be precisely determined from the provided evidence.
Key Points
- Lisdexamfetamine and dextroamphetamine sulfate have different pharmacological profiles.
- The conversion of lisdexamfetamine to d-amphetamine influences its effects.
- Direct comparison studies between the two medications are limited, making it challenging to determine an exact equivalent dose.
- Clinical judgment and potentially adjusting the dose based on patient response are necessary when switching between these medications.