Most of my drawers pull out and then lift up the front to remove. On some, the drawer clasp (the part with 2 rollers) interferes with the removal process. You will probably need to remove this clasp in order to pull the drawer out and up. You might consider notching the drawer back once removed to make this an easier process in the future.
With the full extension drawer guides, with the drawer pulled fully open, there is a small black lever on each side, about the middle of the drawer. Push one down and the other up to release the drawer.