What is prodrug?

A prodrug is a drug that is inactive when you take it (when it is administered), but then becomes active once your body starts to break it down (usually through metabolism). Stimulant simply refers to a class of drug. The opposite would be a non-stimulant. However, it is a different adjective describing the drug and is not part of "prodrug". That is, to be clear, the drug you're looking at is both a stimulant and a prodrug.