Switching from Vyvanse 70mg to Mydayis Dosing
When switching from Vyvanse (lisdexamfetamine) 70mg to Mydayis (mixed salts of a single-entity amphetamine product), the recommended starting dose is 37.5mg of Mydayis once daily.
Conversion Rationale
Vyvanse 70mg is the maximum recommended dose of lisdexamfetamine 1, which is a prodrug that is converted to dextroamphetamine in the body 2. When switching between amphetamine formulations, it's important to consider:
Pharmacokinetic differences:
- Vyvanse (lisdexamfetamine) is a prodrug that requires enzymatic conversion to active dextroamphetamine 3
- Mydayis contains mixed amphetamine salts in a triple-bead delivery system
Duration of action:
- Vyvanse provides approximately 12 hours of coverage 4
- Mydayis is designed to provide coverage for up to 16 hours
Dosing Algorithm
Initial conversion:
- For patients on Vyvanse 70mg (maximum dose):
- Start with Mydayis 37.5mg once daily in the morning
- For patients on Vyvanse 70mg (maximum dose):
Titration schedule:
- Evaluate response after 1 week
- If needed, increase by 12.5mg increments weekly
- Maximum Mydayis dose: 50mg daily for most adults
Monitoring parameters:
- Efficacy: Symptom control throughout the day
- Side effects: Insomnia, appetite suppression, cardiovascular effects
- Vital signs: Blood pressure and heart rate at each visit
Clinical Considerations
- Timing of administration: Both medications should be taken in the morning to minimize sleep disturbances
- Duration differences: Patients may notice longer coverage with Mydayis (16 hours vs 12 hours with Vyvanse)
- Adjustment period: Allow 1-2 weeks for the patient to adjust to the new medication before making further dose changes
Common Pitfalls to Avoid
- Starting at too high a dose: Beginning with the maximum dose of Mydayis can increase side effects
- Inadequate monitoring: Failure to assess both efficacy and side effects during the transition
- Abrupt discontinuation: Stopping Vyvanse suddenly before starting Mydayis
- Ignoring patient feedback: Not considering the patient's experience with the duration and quality of symptom control
Special Situations
- Patients with renal impairment: Consider lower starting doses and more gradual titration
- Patients with cardiovascular conditions: More frequent monitoring of vital signs during the transition
- Patients with comorbid anxiety: Watch for potential exacerbation of anxiety symptoms
By following this structured approach, the transition from Vyvanse 70mg to Mydayis can be accomplished safely while maintaining effective symptom control.