Impairment in cochlear function produced by chloramphenicol and noise

Ototoxic interaction between chloramphenicol and noise was studied in two separate investigations. In the first study, permanent ototoxicity was demonstrated in a group of rats which were subjected to short-duration, high-intensity noise and were then given chloramphenicol orally. The anatomical damage in this group was consistent with observed changes in cochlear round window recordings of cochlear microphonics at 4 kHz and of the N1 component of the eighth nerve action potential. In the second study, a temporary depression in the function of the cochlea was observed in rats subjected to the noise-chloramphenicol regimen used in the first study. Depressions in recordings of the round window similar to those in the first study were seen only during the first five days of recordings. After the fifth day, the recordings of the round window were normal, indicating recovery from a temporary shift in threshold produced by chloramphenicol and noise. Incidence of purulent otitis media was found in 57 and 0% of the animals in the first and second studies, respectively. The combination of chloramphenicol and noise appears to be responsible for the production of temporary cochlear deficits. The addition of the third variable, otitis media, appears to result in permanent impairment of the cochlea.