Effects of inhaled amikacin on racehorses with history of poor performance and comparison with intravenous administration

Aim of the present study was to evaluate the effect of inhaled amikacin, compared with systemic administration, on tracheal wash (TW) cytology and bacteriology and on clinical scoring in racehorses with presumptive Inflammatory Airway Disease (IAD). Thoroughbred racehorses (n=16) with history of poor performance and positive results of TW bacteriology and amikacin sensitivity test were selected. The horses were then randomly divided in 2 groups: 8 horses (group A) were treated with 3,3 mg/kg of inhaled amikacin q24h for 10 days, 8 horses (group B) received 10 mg/kg of amikacin intravenously q24h for 10 days. Values of clinical score, TW neutrophils differential count and colony forming units/ml (CFU/ml) before and post-treatment (PT) in both groups were compared by Student-T test. Rate of recurrence of bacterial isolation PT between the groups was compared with Chi-squared test. In group A, a significant decrease in clinical score (p < 0,01), TW neutrophils differential count (p < 0,05) and CFU/ml (p < 0,01) was found. In group B a significant decrease in clinical score (p < 0,05) and CFU/ml (p < 0,01) was observed. No difference in bacterial isolation PT was found between groups. In conclusion, inhaled amikacin at a dosage of 3,3 mg/kg q24h for 10 days appeared to be effective in the reduction of clinical score, TW neutrophils percentage and bacterial CFU/ml. The absence of a significant difference between the two groups in the isolation of bacteria PT suggested the effectiveness of inhaled amikacin.