Ototoxicity of different concentrations povidone-iodine solution applied to the middle ear cavity of rats

To investigate the ototoxic effects of different concentrations of povidone-iodine solutions applied to the middle ear cavity of rats using distortion product otoacoustic emissions. 24 healthy 3-3.5-month-old adult female Sprague-Dawley rats were randomly divided into three groups. The group A (n = 8 ears) received 5 % povidone-iodine solution to the right ear, the group B (n = 8 ears) received 7.5 % povidone-iodine solution to the right ear and the group C (n = 8 ears) received 10 % povidone-iodine solution to the right ear. All animals received saline solution to the left ear as a control (n = 24 ears). The animals were tested before, 1 and 10 days after solutions administration to the middle ear. The resulting distortion product otoacoustic emissions were evaluated at 1.5, 2, 3, 4, 5, 6, 7, 8, 10 and 12 kHz. Statistically significant reductions in DP-gram amplitudes were noted at high frequencies (7, 8, 10, 12 kHz) in the group A at day 1 but this effect return at day 10. In group B and group C statistically significant differences were recorded for low and high frequencies (1.5, 2, 7, 8, 10, 12 kHz) according to the control group at day 1 and 10. 7.5 and 10 % povidone-iodine showed a significant ototoxic effect on day 1 and 10. But this toxic effect could not be elicited in 5 % povidone-iodine group on day 10. The present study revealed that commercially available high concentration povidone-iodine solution may cause significant ototoxic effects when applied topically through a perforated ear drum in rats. Based on results of this experiment, high concentration povidone-iodine solutions should not be used for preoperative surgical site cleansing for otologic surgery.