Many times, we have to bill multiple vials of the same drug. The CPT code is the same, but the NDC's are different. We bill Vial #1 with KP modifier, and Vial #2+ with KP modifier. Does it matter how many times we need to use the KP modifier? Do we continue to use it on all the 2nd and additional vials of the same drug? Where can I find examples of this billing? Thanks in advance!