If the «dribbles» are more than dribbles, or if the antibiotic doesn't stop the problem, consider any factors that may be making your bunny
feel insecure (new
pet, house guests, change in location of cage, etc.), any of which can cause a bunny to mark her cage more enthusiastically (similar to someone having a dispute with a neighbor about the location of a fence setting up a flag at the property boundary marker).