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The stability of Bacitracin Zinc in a Hydrous Cream Ointment?
I have a customer who is wanting a triple antibiotic ointment cream with the usual active ingredients :Polymyxin B Sulfate 5000 units, Bacitracin Zinc 400 units, and Neomycin 3.5mg. Along with this, they want the inactive Manuka Honey at 10% in their formulation. They want this to be a hydrous ointment. However, their previous formulation group has seen significant decrease of the Bacitracin throughtout their production batch. From the results, it decreased out of specification towards middle and end of the batch.
Researching the two Neosporin products, I noticed their hydrous cream doesn’t have Bacitracin at all. Their anhydrous does however.My main question as I am trying to help save this customer’s product launch is if Bacitracin can be stable in a hydrous system and if so, how should I got about doing it? -
2 Replies
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Judging from your information, you’d need to somehow insulate the bacitracin from the water. From what I know of OTC drugs, the launch is not looking good.
If you’re making an emulsion, it’s at least conceivable that you could suspend/dissolve enough bacitracin in the oil phase to protect it from the water. Proving that this works would probably require a complete re-do of your stability studies, though.If you are making a hydrous ointment without any oil, though, AND all your lab batches are initially stable and have passed long-term stability testing, your only hope is going to be figuring out what is going on in production.The first thing to consider is - Where is the bacitracin going? I’ve noticed that this is a blind spot among many pharma people. Chemicals and active ingredients don’t just vanish - if the assay is low, and the right amount went into the batch - Where is the rest of it? Can you prove it’s being degraded into parts that do not assay as bacitracin? There seems to be a distressing tendency to just accept out-of-spec-low results as failures.If it is being degraded, now you have to figure out what is destroying the bacitracin as processing continues. You’d need to investigate several possibilities. Is it shear? Heat? Contamination? Reaction with the vessel/pump materials? Insufficient batch turnover/mixing leading to concentration gradients? Is the bacitracin separating out for some other reason? If so, where in your processing system is it? -
Below is a quote from sciencedirect, which shows that anhydrous bacitracin powder or bacitracin zinc powder is stable, while hydrous are not.
Dry bacitracin is quite stable at temperatures as high as 37°, but shows definite decomposition at 56° and 80°. Aqueous solutions, adjusted to pH 5 to 7 with or without buffers, are stable for several months at refrigerator temperature, but lose activity rapidly at room temperature. Bacitracin ointments prepared with anhydrous grease bases show good stability at room temperature, but attempts to prepare a stable water-miscible ointment have been unsuccessful.
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