Efficacy of tamoxifen for the treatment of severe equine asthma.

Abstract

BACKGROUND: Tamoxifen, a selective estrogen receptor modulator, decreased airway neutrophilia and improved clinical signs in an experimental model of equine asthma, and induced neutrophilic apoptosis in vitro. HYPOTHESIS/OBJECTIVES: Tamoxifen reduces airway neutrophilia and improves lung function in severe asthmatic horses. ANIMALS: Twelve severe asthmatic horses from a research herd. METHODS: Randomized controlled blinded study design. The effects of a 12-day oral treatment with tamoxifen (0.22&#x2009;mg/kg, q24h) or dexamethasone (0.06&#x2009;mg/kg, q24h) on lung function, endoscopic tracheal mucus score and bronchoalveolar lavage fluid cytology were compared. RESULTS: Tamoxifen significantly improved the pulmonary resistance (R; mean reduction of 1.15&#x2009;cm HO/L/s [CI: 0.29-2.01, P =&#x2009;.007] on day 13), but had no effect on the other variables evaluated. Dexamethasone normalized lung function (mean reduction of Rof 2.48&#x2009;cm HO/L/s [CI: 1.54-3.43, P <&#x2009;.0001] on day 13), without affecting airway neutrophilia. CONCLUSIONS AND CLINICAL IMPORTANCE: Results of this study do not support the use of tamoxifen at the dose studied as an antineutrophilic medication in the treatment of asthmatic horses in chronic exacerbation.