Establishment of a Method to Allow Microbial Limit Testing of Iodine-containing Preparations

Abstract

Background: Contamination of pharmaceuticals with microorganisms may lead to deleterious effects on the therapeutic properties of the drug, and may potentially cause injuries to intended recipients. Iodine can inhibit and kill microorganisms in pharmaceutical preparations. The risk of microbial contamination of cellular products can be reduced when cultured in the presence of iodine. This however, may impact the sensitivity of microbiological tests. Iodine-containing Preparations does not guarantee sterility but may just reduce the proliferation rate of microorganisms, microbiological testing of medicinal products remains obligatory. Thus, an appropriate method to test for microbial contamination of iodine-containing products has to be validated. Objective: To establish a method that would allow microbial limit testing of four iodine-containing preparations (concentrated iodine tincture, compound iodine oral solution, iodine tincture, and iodine glycerin). Methods: To specifically determine the degree of contamination in the four in-house iodine preparations, sodium thiosulfate was used to reduce the iodine molecules to iodide ions, thereby eliminating the intrinsic antibacterial property of the preparations. Then, the suitability of this method was evaluated according to the regulations for non-sterile microbial limit tests. Results: The neutralization method effectively eliminated the interference of the antibacterial iodine component, rendering the control bacteria detectable. The recovery ratio of the test strains met the required standards. Conclusion: The neutralization method with sodium thiosulfate as the iodine neutralizer is suitable for microbial limit testing of concentrated iodine tincture, compound iodine oral solution, iodine tincture, and iodine glycerin, with the results being accurate and reliable.