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March 2012


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Jelena Peric <[log in to unmask]>
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The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Thu, 8 Mar 2012 02:49:44 -0800
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Dear All,
have you ever tested the antimicrobial efficacy (i.e. efficacy of antimicrobial preservation) according to EP 5.1.3., or USP, on an antibiotic oral solution, or in any other antibiotic preparation that contains preservatives in addition to the antibiotic?
The test is usually used to demonstrate that the chosen preservative concentration in a product is effective. During developmental stages of a product, different probes with different preservative concentrations are usually tested in order to demonstrate that the choice of a preservative and its concentration is justified, and that the product still complies even if the preservative content drops for what ever reason during shelf life. 
In my case, the situation is more complicated because of the presence of the antibiotic. What would be the right experimental design in my case? 
The simplest way would be to do the test on the final formulation, and to claim that the product is adequately preserved - but by doing so, I would not find out which test microorganisms are inhibited by the preservative, and which ones by the antibiotic, and what happens if the content of any of the antimicrobial substances drops during shelf life.
Maybe I should test the final product formulation with the targeted preservative concentration, and than the same formulation but with the preservative concentration lowered (for example, 80% of the targeted concentration). Maybe I should see what happens if the content of the antibiotic drops to 80%, or what happens in the placebo (without the antibiotic) with the targeted preservative concentration or the lowered preservative concentration...
What would you do in this case?
Any thoughts will be appreciated,

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