Bacitracin is quite effective locally against a wide variety of Gram-positive micro-organisms, including Staphylococcus, beta hemolytic Streptococcus, Pneumococcus, Clostridium welchii, some of the actinomycetes, Treponema pallidum, and others. Its nephrotoxic properties and irritative local effects when injected intramuscularly have precluded its use except as a topical application, where it has been used with great success.
Neomycin is very effective locally against Gram-negative and Gram-positive organisms. However, the hepatotoxic and ototoxic properties of neomycin preclude its systemic adminstration. Some patients with hemolytic Streptococcus and B. pyocyaneus (Pseudomonas aeruginosa) infections, in a series treated by Kile, did not respond satisfactorily to neomycin ointment.
Since both bacitracin and neomycin are not used systemically and since the two together are effective against all Gram-negative and Gram-positive organisms, a combination of the two in a petrolatum ointment base containing 500 units of bacitracin and 5 mg. of neomycin sulfate per gram of base* was