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Brien C. David, Lynne S. Gearinger, June Klingensmith, Heleen H. Decory; Twenty-Eight Day Microbial Preservative Efficacy of Loteprednol Etabonate Ophthalmic Ointment, 0.5%; an Unpreserved Ointment with Low Water Activity. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6274.
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© ARVO (1962-2015); The Authors (2016-present)
Loteprednol etabonate ophthalmic ointment, 0.5% (Lotemax ointment) does not contain a preservative due to its low water activity. The purpose of this study was to conduct a Preservative Efficacy (PE) test on Lotemax Ointment to confirm that the unpreserved ointment demonstrates inherent biostatic properties.
Three lots of Lotemax ointment (including one expired lot) were evaluated for PE testing following USP <51> guidelines against 5 USP PE microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Aspergillus brasiliensis), 2 field isolates (Serratia marcescens, Bipolaris australiensis), 1 clinical isolate (Stenotrophomonas maltophilia), and 1 American Type Culture Collection (ATCC) fungal strain (Fusarium solani) representing a total of 5 bacterial and 4 fungal strains. Product was heated to not more than (NMT) 44°C, inoculated with ~106 CFU/mL challenge microorganism, and incubated at 20-25°C. At Day 7, 14 and 28 post-inoculation, the test products were removed from incubation and heated to NMT 44°C. Aliquots were transferred into similarly heated isopropyl myristate, and dilutions thereof were filtered for quantitative membrane colony count recovery.
A reduction in microorganism levels was observed for all challenge microorganisms at day 7, 14, and 28 for all three lots evaluated.
The results of this study confirm that the inherent low water activity (<0.6) of the Lotemax Ointment does not provide an environment for microbial growth.
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