Pharmacopoeial specifications and effect of dilution on bactericidal activity of commercially available povidone iodine solutions in Iran

According to several manufacturers of povidone iodine solution in Iran, the quality of the commercially available povidone iodine solutions were evaluated according to the pharmacopeial criteria. The effect of dilution factor on the antibacterial action of the products was also investigated. In this experimental study, pH, contents of available iodine and iodide of the products were determined according to BP 2009 using sodium thiosulfate. Staphylococcus aureus ATCC 29737 and Pseudomona aeroginosa ATCC 28753, as the gram positive and gram negative indicator, were used in this study. The microbicidal activities of different dilutions (1, 1/5, 1/10, 1/20, 1/30, 1/40, 1/60, 1/80, 1/100, 1/200 and 1/300) of domestic as well as imported brand products were evaluated in the periods of 15, 30, 60 and 120 seconds. All of the formulations were within the accepted pharmacopoeial limits. Bactericidal effect of the products increased with the degree of dilution, although the optimum dilution factor was different for each product. The most effective dilution titer was 1/10 in 15 seconds which was much better than the undiluted solution probably due to decrease in free iodine value which affects antibacterial activity of the product. Higher dilutiontiter was less effective. The dilution factor is a critical criterion in povidone iodone products to achieve its optimal antibacterial effects due to the variation of free iodine in individual commercially available products which could also affect their available iodine.