Remicade is considered a treatment. If the doctor accepts Medicare or the hospital infusion center accepts Medicare, then they agree to accept what Medicare pays as payment in full. Now the medication itself might be what you are referencing.
Have you talked to the infusion center's billing office? What are they telling you?
Also I refer you to this notice put out by the maker of Remicade:
http://www.remicade.com/remicade/assets/IN05755.pdf
Unless somethin has changed, you might find this helpful. Be sure to look at the second side of the flyer.