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Aceto81 ★ Belgium, 2009-04-28 16:29 (6256 d 08:12 ago) Posting: # 3628 Views: 11,241 |
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Hi, I know this is Off Topic, but maybe someone can point me in the right direction, or know some forum where someone can help me? I'm performing a preservative efficacy test on an oil based pharmaceutical product. After trying with different preservatives (benzylalcohol, methyl and propylparahydroxybenzoate, propyl galate, some combinations) and different concentrations (up to 4 mg methylparahydroxybenzoate, just to test) the conclusion is always the same: PET test failed. Now I'm wondering if it's possible the innoculum forms some micels in the oil, so that the preservative won't be able to do his job? Any ideas about what is going on, or how to get the test passed? Or is this test not needed in oil based formulations? Best regards Ace |
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g.sharma ☆ 2009-05-19 16:55 (6235 d 07:45 ago) @ Aceto81 Posting: # 3705 Views: 9,167 |
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Is this a liquid formulation or semisolid formulation? |
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Aceto81 ★ Belgium, 2009-05-19 19:32 (6235 d 05:08 ago) @ g.sharma Posting: # 3710 Views: 9,116 |
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❝ Is this a liquid formulation or semisolid formulation? The product where this topic was about is a liquid formulation, but in the mean time we have got the same problem with a semisolid formulation. Ace |
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g.sharma ☆ 2009-05-20 15:46 (6234 d 08:55 ago) @ Aceto81 Posting: # 3717 Views: 9,105 |
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❝ ❝ Is this a liquid formulation or semisolid formulation? ❝ The product where this topic was about is a liquid formulation, but in the ❝ mean time we have got the same problem with a semisolid formulation. @aceto It has been seem that pareben give good results with oil based formulations. please ensure that you add presevative in the phase it has higher solubility and dissolve before making the final formulations. It has been observed with Partitioning studies poor correlation between aqueous solubility and content of the preservatives in the aqueous phase of the emulsion. Incorporation of preservative into different microscopic structures of the emulsion is proposed as a reason for such effect. Higher concentration of antimicrobials or their combination may be required for efficient preservation of submicron emulsions. gary |
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Aceto81 ★ Belgium, 2009-05-26 12:21 (6228 d 12:20 ago) @ g.sharma Posting: # 3759 Views: 9,072 |
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❝ It has been seem that pareben give good results with oil based ❝ formulations. ❝ please ensure that you add presevative in the phase it has higher ❝ solubility and dissolve before making the final formulations. I'm sure it was fully dissolved before making the final formulation. In our oil based solution, which is clear, we can see wether it's dissolved or not. We even took an aliquote and put it in the refrigerator to ensure the solubility won't be a problem. ❝ Higher concentration of antimicrobials or their combination may be ❝ required for efficient preservation of submicron emulsions. Higher than 4mg/ml methylparahydroxybenzoate in combination with 2mg/ml propylparahydroxybenzoate? This was the highest concentration we tested with no results.... Thanks for your help Ace |
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larissabsouza ● 2011-04-28 05:53 (5526 d 18:48 ago) (edited on 2011-04-28 10:20) @ Aceto81 Posting: # 6951 Views: 8,541 |
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Hi, I know has been a long time since you posted this. I'm having exactly the same problem in my PET on an oil based formulation. Did you figure out how to get the test passed? How were you preparing the innoculum? Regards, Larissa Edit: Full quote removed. Please delete anything from the text of the original poster which is not necessary in understanding your answer; see also this post! [Ohlbe] |
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Aceto81 ★ Belgium, 2011-04-28 12:45 (5526 d 11:56 ago) @ larissabsouza Posting: # 6961 Views: 8,590 |
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Hi, finally we had some discussions with a microbiologist, and the conclusion was using the determination of water activity and using this very low value to prove that there isn't any bacterial growth allowed. We aren't sure this is 100%waterproof, but it was the best we had. If you can find a better way, please do post. Good luck Ace |
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