Can you mix pristiq and Vyvanse?

I have been on Pristiq 50mg and Vyvanse 70mg daily for 2 years. The worst side effects I've had are jaw clenching/teeth grinding, loss of appetite, and mild insomnia. HOWEVER, there is a possibility of the Vyvanse increasing your risk of serotonin syndrome from the Pristiq (you can check drug interactions at drugs.com for more info). Best advice would be to ask your doc if you're concerned.