Gramicidin formulations

When it was realized that tyrothricin was a mixture of antibiotics, the same principle was applied to gramicidin 62 65 64 65. The addition of quaternary pounds to gramicidin formulations to increase the solubility of the antibiotic in aqueous solution has been utilized66 67. 

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. 

Neosporin [Pfizer], Proprietary formulation of polymyxin B sulfate, neomycin sulfate, and gramicidin. 

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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