They confused the hell out of us on this one. Our kinetics prof. said that with a dose-dependent pharmacokinetic changes, the PK parameters (k, clearance) change.
Found a good-explanation here: http://www.uiowa.edu/~c046138/tut-nonlin.htm
I think there are other contexts of "dose-dependent" that have a completely different meaning, so you'd need to clarify your question if I didn't answer it.