Summary Background Inhaled corticosteroids are effective for the treatment of equine asthma but they induce cortisol suppression with potential side effects. Objectives To study the efficacy of ciclesonide, an inhaled corticosteroid with an improved safety profile, on lung function, clinical signs related to airway obstruction, and serum cortisol levels in asthmatic horses exposed to a mouldy hay challenge. Study design Cross‐over placebo controlled, blinded, randomised experiment. Methods Sixteen horses were enrolled in three subsequent dose‐titration studies (8 horses/study) to investigate the effects of inhaled ciclesonide administered for 2 weeks at doses ranging from 450 to 2700 μg twice daily or 3712.5 μg once daily. Systemic dexamethasone (0.066 mg/kg per os) was our positive control. A placebo group was also studied. Lung function and clinical scores were blindly performed before and after 7 and 14 days of treatment. Serum cortisol was measured before and after 3, 5, 7, 10, 14 days of treatment as well as 3 and 7 days post treatment. Results After 7 days, dexamethasone induced a significant reduction in pulmonary resistance (from 2.5 ± 0.6 at day 0 to 1.1 ± 0.7 cm H2O/L/s), pulmonary elastance (5.0 ± 2.6 to 1.2 ± 1.0 cm H2O/L), and of the weighted clinical score (14.8 ± 4.7 to 8.0 ± 4.4). Similarly, ciclesonide 1687.5 μg twice daily significantly improved pulmonary resistance (2.7 ± 1.1 to 1.6 ± 0.8 cm H2O/L/s), pulmonary elastance (5.2 ± 3.1 to 2.2 ± 1.3 cm H2O/L), and weighted clinical score (13 ± 2.9 to 10.8 ± 4.2). Serum cortisol suppression (<50 nmol/L) systematically occurred with dexamethasone from day 3 of treatment up to day 3 post treatment, but not with ciclesonide at any tested doses. Placebo did not exert any significant beneficial effect. Main limitations Experimentally induced asthma exacerbations in horses might respond differently to treatment than naturally occurring exacerbations. Conclusions Inhaled ciclesonide is an effective treatment for horses with equine asthma. Serum cortisol was unaffected by treatment.

Administration of budesonide with the Respimat based inhaler provided dose-dependent relief of airway obstruction in horses with severe asthma, but also a suppression of serum cortisol.

The study indicated that the bronchodilatory properties of NBB were not statistically different from those of atropine, but were of shorter duration. N-butylscopolammonium bromide was associated with fewer systemic side effects, and therefore NBB should be preferred over atropine when assessing the reversibility of airway obstruction in horses.

Increased expression of COX-2 in gastric ulcers of the squamous portion of the stomach in horses suggested a role for this enzyme in gastric ulcer healing.

The transendoscopic gastric biopsy technique described here is a feasible, safe and useful technique for obtaining samples from the equine gastric glandular mucosa. Although biopsy samples could be obtained from several areas in the nonglandular mucosa, these were very small, took longer to heal and were not considered adequate for histopathological evaluation, and another technique should therefore be validated.