Is there a formulation for ear drops with rifampicin?

I do not know any composition for such ear drops, which, according to your explanation, are used for the external auditory canal. In such cases, the use of a watery excipient is not recommended but rather a semipolar solvent. DMSO proves to be the only usable solvent, taking into account an intact eardrum. DMSO seems to occur in ear drops for veterinary applications. Perhaps best to consult the NKO-doctor.