Sterisporin is a sterile ophthalmic antibiotic ointment containing Bacitracin Zinc USP (500 U/g) and Polymyxin B Sulfate USP (10,000 U/g). It is used for the treatment of certain types of ocular infections like conjunctivitis caused by bacteria. Supplied in a convenient 3.5 g tube and intended for use. No prescription is required in Canada except in Quebec, where a prescription is required.