Concentrations of gentamicin in serum and bronchial lavage fluid after once-daily aerosol administration to horses for seven days.

This study conducted on horses evaluated the concentrations of gentamicin in serum and bronchial lavage fluid following once-daily aerosol administration of this antibiotic for seven days, and also observed the bronchial tree inflammation related to such administration. No evidence of gentamicin accumulation or respiratory inflammation was detected, indicating that such treatment appears safe and may be clinically useful for treating horses with bacterial airway infections.

Study Design and Methodology

• The study involved 13 healthy adult horses, with 8 horses in the treatment group and 5 horses serving as untreated controls.
• Gentamicin, at a dosage of 20mL of a 50mg/mL solution, was administered via aerosol once a day for a week to the horses in the treatment group.
• Samples of serum and bronchial lavage fluid (BLF) were taken from all horses at the start of the study and then at intervals of 0.5, 4, 8, and 24 hours after the seventh day of gentamicin administration.
• The concentrations of gentamicin were measured in all the samples from the treated horses, and cytological analyses were performed on all BLF samples.

Results

• The maximum median concentration of gentamicin detected in the BLF was 2.50 microg/mL at 0.5 hours post-administration.
• The median concentration of gentamicin in serum was less than 0.50 microg/mL at all the time points measured.
• No statistically significant differences were observed between the control and treatment groups in terms of total nucleated cell counts or differential cell counts in the BLF.
• All horses displayed an increase in the neutrophil count in their BLF above the base level at 4 and 24 hours.

Conclusions

• The researchers found no evidence of gentamicin accumulating or causing inflammation in the respiratory system after a seven-day course of once-daily aerosol administration.
• This regimen does not appear to have the potential to cause local or systemic toxicosis.
• The daily administration of aerosolized gentamicin appears to be a safe procedure, suggesting potential clinical utility in treating horses suffering from bacterial infections in their airways.