Measurement of Free Iodine in Different Formulations of Povidone-Iodine Eye Drops 5.

There are multiple studies in the literature that support the use of povidone iodine in the preparation of the surgical field of cataract as the most effective means to reduce the bacteria present in the ocular surface and the risk of infection. The concentration of free iodine is related to the antiseptic activity of these compounds, being, therefore, a good indicator of its effectiveness. The objective of this study was to determine the amount of free iodine and the evolution of it in different formulations of povidone iodine eye drops. The povidone iodine 5% eye drops were prepared starting from Betadine 10% dermal or the active principle and using a solvent, phosphate-citrate buffer solution, and sodium chloride 0.9% or sterile water for injection. Aliquots of 5 mL were packed in low-absorption absorption eye drops, topaz glass vials, and polyethylene syringe. The determination of free iodine was made by volumetric titration. Titration was performed with 0.1 M sodium thiosulfate using a starch solution as an indicator. Of the 0.1 M sodium thiosulfate, 1 mL is equivalent to 12.69 mg of available iodine, and it is expressed as a percentage of free iodine in the iodized povidone (% free iodine). Eyewash titrations were performed by replacing the substance with 5 mL of eye drops and following the remaining steps. Valuations were made on days 0, 7, and 14, as well as the measurement of pH and osmolarity. The results show that there are no differences between the average results at the three measurements taken on days 0, 7, and 14. We conclude that the free iodine remains stable during the stability period of 14 days. Regarding the pH and osmolarity data, the authors believe that the best tolerated formula will be that elaborated with povidone iodine and a phosphate- citrate buffer solution.