Three-minute nebulization of gentamicin in healthy dogs results in therapeutic concentrations in bronchoalveolar lavage fluid while remaining below the toxic range values in blood

OBJECTIVE To determine and compare the concentration of gentamicin in the lower airways and serum of healthy spontaneously breathing dogs after nebulization with 5% undiluted gentamicin during 3 versus 10 minutes. ANIMALS 10 healthy experimental Beagles. METHODS This was a prospective crossover study. A standardized bronchoalveolar lavage (BAL) procedure was performed in each dog after 1 week of administration of each of 2 different gentamicin nebulization protocols separated by a 1-week washout period. The 2 protocols consisted of nebulization of 5% undiluted gentamicin (50 mg/mL) twice daily either during 10 minutes per session (+/- 95 mg; 10-minute protocol) or 3 minutes per session (+/- 28 mg; 3-minute protocol). BAL fluid (BALF) was obtained under general anesthesia using a bronchoscope within 15 minutes after administration of the last nebulization. Blood was collected within 5 minutes after BALF collection. BALF and serum gentamicin concentrations were determined by particle-enhanced turbidimetric inhibition immunoassay. Concentrations between protocols were compared using a paired t test. RESULTS Both BALF and serum gentamicin concentrations were higher after the 10-minute protocol compared with the 3-minute protocol (mean +/- SD: 2.41 +/- 0.87 mg/L vs 1.25 +/- 0.31 mg/L, P = .001; and 1.02 +/- 0.59 mg/L vs 0.31 +/- 0.24 mg/L, P < .0001 in BALF and serum, respectively), while the BALF-to-serum ratio did not differ between the protocols (3.75 [1.37 to 5.75] (median [IQR]) in the 3-minute protocol vs 2.48 [2.02 to 2.67] in the 10-minute protocol; P = .754). CLINICAL RELEVANCE A 3-minute nebulization of gentamicin seems to achieve sufficient concentrations of gentamicin in the BALF to have good efficacy against aminoglycoside-sensitive bacteria while remaining below the toxic range values in blood.