An antibiotic hip stem would be considered a combination product “as defined by 21 CFR 3.2 (e)”. The primary mode of action of this hip stem would be to provide similar functionality and support of a hip and the antibiotic portion would be considered an additional effect of the implant, and the CDRH would be responsible for this device. Also since this is a combination implantable product it would be considered a Class III device by the FDA . There can be exceptions to this if for example, if the device already has a predicate device with the same design and antimicrobial agent, however the FDA is strict in its definition of antimicrobial agents and the formulations used due to resistance. The claim for the device would be the functionality and support the hip implant provides along with it’s ability to counteract infection and provide stability for the patient with the antibiotic portion. Animal trials would be necessary in preclinical research to prove the infection claim and along with this biocompatibility studies would be key as well. An IDE would be necessary as well in order to receive data from in vivo environment and determine whether the benefits of the antibiotic outweighs the clinical risk of resistance.

Source
https://www.fda.gov/RegulatoryInformation/Guidances/ucm071380.htm#5