Bacitracin formulations

Although tyrothricia is too toxic for parenteral therapy, it was formerly sold in the United States as oral lo2enges. Modem tyrothricin formulations are composed of 70—80% tyrocidines and 30—20% linear gramicidins. Tyrocidines are not as active as linear gramicidins and are too toxic for any therapeutic use by themselves. The bactericidal linear gramicidins are used in the United States solely as an ophthalmic solution in combination with polymyxin B sulfate and neomycin sulfate. The linear gramicidin is used in this aqueous product as a substitute for bacitracin, which lacks stabiUty under such conditions. 

Neomycin is available in numerous topical formulations, both alone and in combination with polymyxin, bacitracin, and other antibiotics. It is also available as a sterile powder for topical use. Gentamicin is available as an ointment or cream. 

Colistin is used primarily for oral treatment of E. coli infections in calves and pigs. Commercial formulations of colistin consist of two main components colistin A and colistin B. Tire ratio between these two components is not constant, while small amounts of other related components are also present as minor constituents. Both polymyxin B and colistin have been frequently used orally in combination with bacitracin or neomycin. 

Bacitracin is a linear-ring peptide antibiotic produced by Bacillus subtilis and Bacillus licheniformis. Commercial formulations of bacitracin comprise a mixture of many closely related compounds classified into bacitracin A, B, C, D, E, F, and G (5). The main components are bacitracin A, B, and B2, constituting 57%, 22%, and 13%, respectively, of the mixture, whereas bacitracin F constitutes less than 2%. Bacitracin F is actually a degradation product of bacitracin A that... 

An IPC-ESI-MS/MS method allowed the simultaneous determination of neomycin and bacitracin in human and rabbit sera [79] and the analysis of aminoglycoside antibiotics in human plasma [80]. IPC was recently validated for the estimation of bulk and formulated gatifloxacin [81]. The IPC determination of norfloxacin in diverse matrices worked as a stability indicating method [82], A CI2 stationary phase with embedded polar group successfully achieved IPC baseline tetracycline separation simply by using a phosphate as the IPR [83], A practical IPC method for the quality control of fosfomycin calcium and its related substances was recently suggested [84],... 

Neomycin is not usually administered parenter-ally to animals because of nephrotoxicity and ototoxicity. Only 3% of a dose of neomycin is absorbed following p.o. administration it is, therefore, used in the therapy of coliform enteritis in small and large animals. It is available as tablets, boluses and water additives, in many different combinations with antibiotics, corticosteroids and anticholinergic agents. It can also be used to decrease nitrogenous waste production by the normal gastrointestinal flora in animals with hepatic encephalopathy. Neomycin is not absorbed through the skin, so it is frequently utilized as the antibacterial constituent in ophthalmic formulations (especially in combination with bacitracin and polymyxin B) and in preparations for the treatment of otitis externa in small animals. 

The bacitracin zinc and polymyxin B sulfate ophthalmic ointment USP is a sterile antimicrobial ointment formulated for ophthalmic use. Bacitracin zinc is the zinc salt of bacitracin, a mixture of related cyclic polypeptides (mainly bacitracin A) produced by the growth of an organism of the lichenlformis group of Bacillus subtilis var Tracy. It has a potency of not less than 40 bacitracin units per milligram. Polymyxin B sulfate is the sulfate salt of... 

Creamy powder contg 1-4% H.O. Less bitter than bacitracin. Soly in water at 25 = 0.23-0.45% (w/w). Solubilities determined by Weiss et al, Antibiot. A Chemother, 7, 374 (1957) in mg/ml at about 28 water 5.1 methanol 6.55 ethanol 2.0 isopropanol 0.16 ethyl acetate 1.3 chloroform 0.01 patr ether 0.025. More stable than bacitracin at room and elevated tempa- Zinc bacitracin can be used in formulations requiring heat processing. 

Tolymyxin B is formulated for delivery in combination with bacitracin, neomycin, gramicidin, oxytetracycline, or trimethoprim. See Chapters 43 through 46 for further discussion of these antibacterial agents. 

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