For a patient with ADHD on Vyvanse (lisdexamfetamine) 40mg OD, would splitting the dose to morning and afternoon alleviate early afternoon tiredness?

Managing Afternoon Fatigue with Vyvanse in ADHD

For a patient experiencing afternoon fatigue while on Vyvanse 40mg once daily, splitting the dose into morning and afternoon administration is not recommended. Instead, the patient should consider switching to a different medication regimen or adding a small afternoon booster dose of a different stimulant.

Understanding Vyvanse Pharmacology

Vyvanse (lisdexamfetamine) is a prodrug stimulant with unique properties that make it unsuitable for splitting doses:

• Lisdexamfetamine is pharmacologically inactive until enzymatically converted to d-amphetamine in the bloodstream, primarily by red blood cells 1
• This conversion process gives Vyvanse long-acting properties designed for once-daily dosing 2
• The medication is specifically formulated to provide extended coverage throughout the day

Why Splitting Vyvanse Doses Is Not Recommended

1. Pharmacokinetic limitations: Splitting a Vyvanse capsule would not create two equal doses due to its prodrug formulation
2. Disruption of intended release mechanism: The medication is designed to be taken as a single dose to maintain consistent blood levels
3. Potential for increased side effects: Irregular dosing could lead to unpredictable peaks and valleys in medication effect

Better Alternatives for Managing Afternoon Fatigue

Option 1: Adjust Vyvanse Dosing (Preferred First-Line Approach)

• Consider increasing the morning Vyvanse dose from 40mg to 50mg or 60mg (within the therapeutic range of 30-70mg daily) 2
• Earlier administration of the morning dose may help extend coverage into the afternoon

Option 2: Add a Small Afternoon Booster Dose

• A small dose of immediate-release methylphenidate (2.5-5mg) in the early afternoon can address the "wearing off" period 3
• This approach maintains the benefits of Vyvanse while addressing the afternoon fatigue

Option 3: Consider Alternative Medication Regimens

• Switching to twice-daily methylphenidate might be appropriate if afternoon fatigue persists 4
• Adderall has demonstrated longer-lasting effects than single-dose methylphenidate and could be an alternative 4

Timing Considerations

• Stimulant medications should be administered early in the day to minimize insomnia 3
• For patients requiring afternoon coverage, the last dose should be taken no later than early afternoon to prevent sleep disturbances
• According to guidelines, methylphenidate is typically administered twice daily (breakfast and lunch) to minimize insomnia 3

Monitoring and Follow-up

When adjusting ADHD medication:

• Assess effectiveness of symptom control throughout the entire day
• Monitor for side effects including insomnia, appetite suppression, and cardiovascular effects
• Schedule follow-up within 2-4 weeks after any medication adjustment 5

Important Caveats

• Splitting Vyvanse capsules disrupts the intended pharmacokinetic profile
• Evening dosing of stimulants increases risk of insomnia and should be avoided
• For patients with specific concerns about medication wearing off, atomoxetine may be considered as it provides "around-the-clock" effects and can be administered in divided doses 3

Remember that the goal is to optimize symptom control throughout the day while minimizing side effects and maintaining quality of life.