Talking Shrubbery, that was actually the exact combination I was on; Klaron, Differin, and Tetracycline. It helped me quite a bit, but it definitely wasn't impossible for me to get a pimple.

I gradually stopped all my prescriptions about a month ago just because I was trying to give my skin a break and I wasn't sure if the effects were wearing off. Going of the medications hasn't had any negative effects for me. I think they helped get my skin under control, but once it calmed down it didn't matter whether I was on meds or not.