Bacitracin stability

As mentioned above, the rectal route is very attractive for systemic delivery of peptide and protein drugs, but rectal administration of peptides often results in very low bioavailability due to not only poor membrane penetration characteristics (transport barrier) but also due to hydrolysis of peptides by digestive enzymes of the GI tract (enzymatic barrier). Of these two barriers, the latter is of greater importance for certain unstable small peptides, as these peptides, unless they have been degraded by various proteases, can be transported across the intestinal membrane. Therefore, the use of protease inhibitors is one of the most promising approaches to overcome the delivery problems of these peptides and proteins. Many compounds have been used as protease inhibitors for improving the stability of various peptides and proteins. These include aprotinin, trypsin inhibitors, bacitracin, puromycin, bestatin, and bile salts such as NaCC and are frequently used with absorption enhancers for improvement in rectal absorption. 

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],... 

Topical corticosteroids are used in cases of exacerbation and should be applied sparingly to the affected area. Hydrocortisone 1% twice a day or dexamethasone 0.1% applied to the periorbital area helps to relieve symptoms during these periods. Secondary infection manifested as blepharitis or keratoconjimctivitis should be treated with topical ophthalmic antibiotic ointments such as bacitracin or erythromycin.Topical antihistamines, NSAIDs, or mast cell stabilizers can be used to control itching, and topical steroids are sometimes required to treat severe keratoconjunctivitis associated with the atopic response. Because of side effects, steroids are not indicated for longterm use. 

Properties Creamy-white powder. Almost insoluble in water. Good thermal stability, usually has 50-60 units/mg of bacitracin activity. 

Although tyrothricin is too toxic for parenteral therapy, it was formerly sold in the United States as oral lozenges. 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 stability under such conditions. 

Many compounds have been used as protease inhibitors to improve the stability of peptides and proteins [28-35], including aprotinin, trypsin inhibitors, bacitracin, puromycin, bestatin, and bile salts (e.g.. 

Resistance to bacitracin does not emerge rapidly in originally susceptible strains. The thermal and storage stability of bacitracin is enhanced by the presence of an equimolar concentration of Zn " and the antibacterial action is potentiated by an excess of Zn " ". It has been suggested that Zn + is also associated with the mechanism of antibacterial action. No chemical assay methods are yet available for bacitracin. For the determination of potency the cylinder plate method with Micrococcus flavus (ATCC 10 240) as test organism is used. ... 

Popular stabilizers in the solubUization buffer are 10 to 20% (w/v) glycerine, 1 mM DTT, and 0.1 to 1 mM EDTA. The protease inhibitors PMSF, bacitracine, trypsin inhibitor, leu-peptin, benzamide, and benzamidine are also a blessing, in that binding activities in solution are more sensitive against protease than in the membrane (see Table 5.1). PMSF irreversibly inhibits serin proteases via covalent derivatization of the active center. A one-time application is thus sufficient, especially because PMSF falls apart in watery solution (half-life of a few hours). 

Bacitracin-cellulose is an efficient affinity adsorbent for isolation of proteolytic enzymes. Its flow properties stability, and the possibility of a repeated use make it a promising adsorbent for large-scale operations. 

Gillissen [104] finds that the antibacterial action of tyrothricin is influenced by the presence of solubilizers. Cationic surfactants have a synergistic effect (as mentioned above) on its activity against Gram-positive and Gram-negative bacteria, whereas polysorbate 80 inhibits its activity. It is thus important that these effects are borne in mind, and a compromise must be found between the stability and incompatibility characteristics of the solution and the activity of the product. The complexity of the situation is revealed by the fact that the activity of bacitracin is enhanced by the presence of cationic and non-ionic surfactants [106] but decreased by anionic agents. The effect of non-ionic surfactants on the bactericidal activity of tyrothricin has been measured [107]. Some results are shown in Table 6.11. 

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