Polymyxin B: What is it? How it is taken and side effects

with antibiotic activity, particularly active against Gram-negative bacteria and belonging to the class of polymyxins. More precisely, it is a cyclic polypeptide of natural origin produced by fermentation from cultures of Bacillus polymixa.

To be fair, polymyxin B is not a single compound but is made up of a mixture of different molecules; however, the main components seem to be polymyxin B1 and polymyxin B2 (shown in the figure below).

Editorial board Polymyxin B1 and Polymyxin B2 - Chemical Structures

Although in other countries polymyxin B can also be administered parenterally, in Italy the only medicines containing the active ingredient in question currently on the market (April 2019) are intended for topical use (more precisely, ear use). In these medicines, polymyxin B is present in combination with other active substances.

Some polymyxin B medicines are classified as SOP (No Prescription Required) drugs, therefore, they can be dispensed without a prescription; others, on the other hand, require presentation of a repeatable medical prescription (RR). In both cases, their cost is fully borne by the citizen.