An in-hospital clinical trial assessing nebulized lidocaine compared to saline for treatment of asthma in horses

BACKGROUND: Corticosteroids are the main pharmacologic treatment for equine asthma (EA) but may have adverse effects in metabolically unstable horses. Recent pilot studies support the use of nebulized lidocaine as an alternative treatment option. HYPOTHESIS/OBJECTIVES: Nebulized lidocaine will improve EA-associated clinical variables and airway inflammation. ANIMALS: Twenty client-owned horses diagnosed with EA. METHODS: Randomized, blinded, in-hospital study comparing 1 mg/kg preservative-free 4% lidocaine (n = 10) nebulized via Flexineb (twice daily for 7 doses) to 0.9% saline control (n = 10). Clinical examination, endoscopy, lung function, bronchoalveolar lavage (BAL) cytology, and inflammatory cytokines in blood and epithelial lining fluid (ELF) were compared between treatment groups using univariate analyses. Global linear models were used to assess covariate impact (P < .05). RESULTS: The effect of treatment on clinical variables (clinical score, lung function, mucus, and BAL cytology) did not differ between saline and lidocaine treated horses. However, the severity of EA as a covariate significantly impacted multiple baseline variables and confounded the effect of treatment type. Saline-treated horses showed significantly larger decreases in ELF tissue necrosis factor alpha (P = .04) and interferon gamma concentrations (P = .03), compared with lidocaine-treated horses, independent of covariates. CONCLUSIONS AND CLINICAL IMPORTANCE: We did not identify a difference in treatment effect of nebulized lidocaine compared to saline on clinical variables in hospitalized asthmatic horses. A longer duration of lidocaine administration or focus on severe EA may be necessary to establish treatment effects. Observed changes in lower airway cytokine concentrations suggest that saline may have more than a placebo effect in treating EA.