Vitrase is effective at deflating HA (hyaluronic acid) fillers like Juvederm, Restylane, and Perlane. It is ineffective for non-HA fillers like Sculptra, Radiesse, Artefil, or Silicone oil.
Vitrase is very safe. However, the enzyme is egg based. So, if you have ever had a reaction to an egg based vaccine, you should be skin tested prior to treatment with Vitrase.
Vitrase can be used to shape and sculpt fullness related to HA filler. However, this type of shaping requires a great deal of experience. If your doctor does not have this level of experience, it is unrealistic to expect them to have this level of finesse. However, given the issue that you are describing, significantly knocking down the volume you have in your lip and filling in more conservatively if needed may be a good option. You and your doctor should do fine with the Vitrase.