High risk — avoid this combination unless there is no good alternative.
Excessive stimulation — racing heart, high blood pressure, severe anxiety, insomnia, appetite loss, and a higher risk of cardiovascular events (chest pain, arrhythmia, stroke). In children and adolescents the combination raises the risk of psychotic symptoms and serotonin syndrome when other serotonergic drugs are also present.
Why this happens (mechanism)
Adderall (mixed amphetamine salts) and Vyvanse (lisdexamfetamine, a prodrug that converts to dextroamphetamine) deliver the same active stimulant. Taking them together is essentially doubling the amphetamine dose.
What to monitor
- Resting heart rate and blood pressure (sitting, ideally before each dose)
- Sleep quality and total sleep hours
- Appetite and weight (especially in children/adolescents)
- Anxiety, irritability, or new mood changes
Dose adjustment
Do not stack. Choose one stimulant and titrate to clinical effect. If switching from one to the other, the prior agent should be stopped — there is no clinical reason to overlap.
Safer alternatives to consider
Standard of care for ADHD; one agent at the right dose is dramatically safer than two.
No cardiovascular stimulant load; useful when stimulant tolerance is poor.
Multimodal treatment outperforms higher medication doses for many patients.
Always discuss alternatives with your prescriber before making any change. The right choice depends on your other medications, conditions, and what is working for you today.