"i was recently diagnosed with adhd and i was first prescribed concerta. since concerta is part instant release and part extended release it starts working extremely quick, within 15-30 minutes, which was nice because there was no need to time things out when taking the medication. unfortunately, concerta starts working immediately and also stops working immediately which for me led a horrific crash. i was irritable and angry after the medication wore off. due to this my doctor switched me to vyvanse. vyvanse is a prodrug which means the actual drug inside the capsule is not therapeutically helpful until it gets broken down in the body. this allows for a nice steady come up and no crash when the medication is eventually excreted."