Why does vyvanse (lisdexamfetamine) make me pee a lot?

Vyvanse (lisdexamfetamine) : Vyvanse (lisdexamfetamine) is an amphetamine or stimulant which can cause dry mouth as a side effect. In turn, drinking water and other fluids to compensate for the dry mouth can cause people to urinate more frequently. Taking Vyvanse (lisdexamfetamine) with orange juice or drinks with vitamin C can reduce the absorption and its effectiveness.