From the FDA Drug Label
The plasma elimination half-life of dextroamphetamine was approximately 8.6 to 9. 5 hours in pediatric patients 6 to 12 years and 10 to 11. 3 hours in healthy adults. Tmax of lisdexamfetamine and dextroamphetamine was reached at approximately 1 hour and 3. 5 hours post dose, respectively. Plasma concentrations of unconverted lisdexamfetamine are low and transient, generally becoming non-quantifiable by 8 hours after administration.
The duration of action of Vyvanse (lisdexamfetamine) is related to the pharmacokinetics of dextroamphetamine, its active metabolite.
- The elimination half-life of dextroamphetamine is approximately 8.6 to 11.3 hours.
- Tmax is reached at approximately 3.5 hours post-dose.
- Lisdexamfetamine itself has a short half-life of less than one hour. Based on the pharmacokinetic data, it is unlikely that Vyvanse would completely lose its effectiveness after only 2 hours. However, individual responses to the medication may vary, and the effectiveness of Vyvanse may decrease over time as the concentration of dextroamphetamine decreases 1.
From the Research
If Vyvanse (lisdexamfetamine) is losing effectiveness after only 2 hours, it is crucial to consult your healthcare provider to adjust your dosage or medication schedule, as the typical duration of action should last 10-14 hours. Several factors could be causing this shortened effect, including your metabolism processing the medication too quickly, stomach acidity levels affecting absorption, or the need for a higher dose 2. Taking Vyvanse consistently with or without food can help maintain steady levels, and avoiding acidic beverages like orange juice or soda within an hour of taking the medication can prevent interference with absorption. Lifestyle factors such as adequate sleep, proper nutrition, and stress management also significantly impact medication effectiveness. According to a review of lisdexamfetamine in adults with ADHD, the medication has demonstrated efficacy in reducing ADHD symptoms and improving overall functioning, executive functioning, and quality of life 2. However, the loss of effectiveness after 2 hours may require alternative strategies, such as adding a small afternoon booster dose of a shorter-acting stimulant or adjusting the dosage, under the guidance of a healthcare provider.
Some key considerations for managing ADHD with Vyvanse include:
- Consistent administration with or without food to maintain steady levels
- Avoiding acidic beverages that can interfere with absorption
- Monitoring for potential cardiovascular effects, as suggested by a systematic review and network meta-analysis 3
- Considering lifestyle factors that impact medication effectiveness, such as sleep, nutrition, and stress management
- Regular follow-up with a healthcare provider to adjust the treatment plan as needed, based on the latest evidence and guidelines.
Given the most recent and highest quality study available 3, it is essential to prioritize the patient's safety and adjust the treatment plan accordingly, taking into account the potential cardiovascular effects of lisdexamfetamine and other ADHD medications.