Endotracheal nebulization of N-acetylcysteine increases airway resistance in cats with experimental asthma

N-acetylcysteine (NAG), a mucolytic and antioxidant, is speculated to cause bronchoconstriction in cats when delivered via aerosol. We hypothesized that in cats with experimental asthma, aerosol delivery of NAG (400 mg cumulative dose) via an endotracheal tube would increase airflow limitation as measured by ventilator-acquired mechanics. After endotracheal drug delivery, airway resistance and inspiratory plateau pressure (Pplat) measurements were obtained in six mechanically ventilated asthmatic cats. Results demonstrated significantly increased airway resistance (P = 0.0007) compared with aerosolized saline control; Pplats were not significantly different (P = 0.059). All cats exhibited at least one adverse effect: excessive airway secretions (n = 3), spontaneous cough (n = 2), unilateral strabismus (n = 1) and post-anesthetic death (n = 1). No adverse reactions were noted with saline aerosol; cough was noted in one cat with methacholine challenge. In conclusion, airway resistance and adverse reactions were documented in all cats after NAG aerosol delivery. Further studies must be performed to evaluate if it is an effective mucolytic and/or antioxidant in cats and to determine if bronchodilator pre-treatment will negate NAG-induced bronchoconstriction. (C) 2010 ISFM and AAFP. Published by Elsevier Ltd. All rights reserved.