In regards to lip injections, it is always important to make sure that the product being used is a hyaluronic acid based filler such as Restylane, Perlane or Juvederm.
If you happen to be dissatisfied with the results, these products can mostly be dissolved quickly and safely with hyaluronidase, which is essentially a dermal filler eraser.
Other products such as Radiesse or Sculptra (which should never be placed in the lips) do not have an antidote.
So go get that lip augmentation you have always dreamed of, just be aware of what product is going to be injected into your lips and be sure to go to an experienced injector.