Characterization of antimicrobial aerosols for administration to horses.

A study was conducted to characterize the aerosols produced by a medical ultrasonic nebulizer using solutions containing antimicrobials appropriate for therapy of equine lower respiratory bacterial infections (gentamicin sulfate and ceftiofur sodium). Test aerosols were generated using an ultrasonic nebulizer and were analyzed using a laser diffraction aerosol particle analyzer. The aerosol was described in terms of the particle size distribution (volume median diameter), span (sample dispersion), and aerosol density (% volume). The particle size distribution and aerosol density of gentamicin and ceftiofur aerosols were affected by the antimicrobial concentration of the solution. All solutions produced aerosols appropriate for delivery of antimicrobials to the intrathoracic airways of the horse, but the gentamicin (50 mg/ml) and ceftiofur (25 mg/ml) solutions offered the optimal combinations of particle size and aerosol density.