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Sudden sensorineural hearing loss secondary to metronidazole ototoxicity

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A 30-year-old Indian gentleman presented to the emergency department of the Royal Victorian Eye and Ear Hospital, Melbourne, with a history of bilateral profound deafness, tinnitus and headache associated with upper- and lower-limb paraesthesia and myalgia. He had been taking metronidazole (400 mg tds) and amoxycillin (500 mg tds) over the preceding 4 days to treat gingivitis. Further questioning revealed that his maternal uncle had experienced identical symptoms while taking metronidazole. Consequently, his metronidazole was immediately discontinued.

After 2 days, he was able to hear faint sounds, and audiography revealed a symmetrical moderate-to-profound sensorineural hearing loss (SNHL) (Box, A). As per our hospital protocol for SNHL management, oral prednisolone was administered (50 mg daily), followed by a slow wean over 3 weeks.

After 8 days, subjective hearing and paraesthesia had improved, and his headache had abated. Audiometry indicated moderate SNHL up to 2000 Hz, with persisting severe high-frequency SNHL (Box, B).

At 6 weeks, repeat audiogram indicated that hearing was normal up to 2000 Hz, but severe-to-profound high-frequency SNHL persisted (Box, C).

Metronidazole is a nitroimidazole antibiotic widely used in various medical specialties. Common side effects include nausea, diarrhoea and abdominal…