Ototoxicity of intratympanic docusate sodium and mineral oil in the guinea pig

Objectives. (1) To evaluate the ototoxic potential of docusate sodium and mineral oil and (2) to compare the cerumenolytic properties of these agents to water and a commercially available product. Study Design. Prospective animal study. Setting. Docusate sodium and mineral oil are being used to dissolve cerumen plugs. Their ototoxicity has never been assessed. Methods. Nineteen guinea pigs represented 38 ears, which formed 4 groups. Each group was injected with an intratympanic solution once a week for 4 weeks. Group 1 was injected with a negative control solution of saline, group 2 with docusate sodium, group 3 with a positive control solution of gentamicin, and group 4 with mineral oil. Auditory brainstem responses (ABRs) were recorded before any procedure and 1 week after the final injections. Cochleas were analyzed under scanning electron microscopy. The cerumenolytic properties of water, docusate sodium, mineral oil, and cerumol were evaluated. Results. There was no significant ABR threshold increase for saline or mineral oil. Gentamicin and docusate sodium caused a significant threshold increase that averaged 51.9 dB and 44.9 dB over all the frequencies (P <.001). Electron microscopy could not be performed on the cochleas treated by docusate sodium because of very severe osteitis. All of the agents tested seemed to be effective cerumenolytics compared with no treatment, but water was significantly more effective compared with any of the other tested products (P<.001). Conclusion. Docusate sodium was severely ototoxic, and its use should be discouraged. Mineral oil was not ototoxic. Water seemed to be the most effective cerumenolytic agent.