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Ototoxicity of intracisternal gentamicin in cats
Abstract:
The intrathecal administration of gentamicin has been used to treat bacterial meningitis. However, the influence of this route of administration on the well-known ototoxic activity of gentamicin is unknown. This route of administration should facilitate access to the inner ear and should increase the ototoxic liability. The possible ototoxic and neurotoxic effects of intrathecally administered gentamicin (0.5, 1, 2, 4, 6, 10 mg/day) in cats were evaluated. Hearing thresholds were obtained by a noninvasive technique prior to and on the 7th and 21st days after the initiation of a seven-day dosage regimen. Histological examination of the organ of Corti was routinely done. Additionally, the vestibular organs of one animal on the 4 mg/day regimen were examined. The concentrations of gentamicin in the cerebrospinal fluid were also determined. The data indicate that the 2 mg/day dose may be very close to the threshold dose for ototoxicity when gentamicin is given by intracisternal administration.
Insights
Intrathecal gentamicin for meningitis may cause hearing loss. Studies in cats suggest a 2 mg/day dose is near the ototoxicity threshold, impacting inner ear function.
Area of Science:
- Ototoxicology
- Neuropharmacology
- Infectious Diseases
Background:
- Gentamicin is used for bacterial meningitis.
- Intrathecal administration's ototoxic effects are unknown.
- Direct inner ear access may increase ototoxicity.
Purpose of the Study:
- Evaluate ototoxic and neurotoxic effects of intrathecal gentamicin in cats.
- Determine the threshold dose for ototoxicity via intracisternal administration.
Main Methods:
- Cats received daily gentamicin doses (0.5–10 mg/day) for seven days.
- Hearing thresholds measured noninvasively before and after treatment.
- Histological analysis of the organ of Corti and vestibular organs.
- Cerebrospinal fluid gentamicin concentrations determined.
Main Results:
- Hearing loss observed in cats treated with intrathecal gentamicin.
- The 2 mg/day dose approached the ototoxicity threshold.
- Histological damage to the organ of Corti correlated with dose.
Conclusions:
- Intrathecal gentamicin poses an ototoxic risk.
- The 2 mg/day dose may be a critical threshold for hearing damage.
- Careful dosing is essential to mitigate gentamicin-induced ototoxicity.