Summary Background Inhaled corticosteroids are effective in the treatment of equine asthma. A recent study reported that nebulisation of injectable dexamethasone had low systemic bioavailability in healthy horses and could represent a cost‐effective therapy for equine inflammatory lung diseases. Objectives To determine the effects of dexamethasone nebulisation on lung function in severe asthmatic horses. It was hypothesised that dexamethasone administered by nebulisation would be more effective than the same dose administered orally. Study design Randomised blinded experimental study in severe asthmatic horses. Methods Twelve severe asthmatic horses in clinical exacerbation were randomly assigned to treatment with 5 mg of dexamethasone sodium phosphate by nebulisation (n = 6) or by oral administration (n = 6), once daily for 7 days. Lung function was evaluated at baseline, after four treatment days (D4) and 24 h after the last dose (D8). The presence of residual bronchospasm was assessed on D8 with N‐butylscopolammonium bromide administration (0.3 mg/kg i.v.). A respiratory clinical score was performed daily. Serum cortisol concentration was measured at baseline, D4 and D8. Results The pulmonary elastance was unchanged in both groups while pulmonary resistance was significantly improved in the oral group on D8 (mean reduction in 1 cm H2O/L/s [CI: 0.34–1.65, P = 0.003]). All horses had residual bronchospasm at the end of the study. There was a group difference in the respiratory clinical score as it was significantly reduced in the oral group, from D5 to D8. Serum cortisol concentration decreased in all subjects. Main limitations Low number of horses and lack of placebo group. Conclusions Considering the lack of improvement of lung function and the hypothalamic‐pituitary‐adrenal axis suppression, the results of this study do not support aerosolisation of an injectable form of dexamethasone for the treatment of severe equine asthma at the dose and with the nebuliser evaluated.

Background Hay feeding is considered the main triggering factor for airway obstruction and inflammation in severe equine asthma (SEA). Finding alternate strategies allowing hay feeding while controlling clinical signs of SEA is of importance. The Nutri‐Foin Système is believed to decrease inhaled dust by incorporating soybean oil to mechanically processed hay. Objectives We compared airflow obstruction and airway inflammation in horses with SEA fed oiled hay or alfalfa pellet regimen. Study design Controlled trial in asthmatic research horses. Methods Twelve horses in exacerbation of SEA from a research herd were studied. Horses were fed either oiled treated hay (n = 6) or alfalfa pelleted hay (n = 6) for 3 months while being stabled. Lung function, bronchoalveolar lavage fluid cytology and serum antioxidant enzyme kinetics were sequentially evaluated. Results Pelleted hay and the hay treated with the Nutri‐Foin Système similarly improved lung function, airway neutrophilia and serum antioxidant enzyme kinetics over time. Main limitations The small number of horses in each group. Conclusions We conclude from this study that Nutri‐Foin Système is an appropriate alternative to pelleted hay for the control of the airway obstruction in horses with SEA.

BackgroundTamoxifen, 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/ObjectivesTamoxifen reduces airway neutrophilia and improves lung function in severe asthmatic horses.AnimalsTwelve severe asthmatic horses from a research herd.MethodsRandomized controlled blinded study design. The effects of a 12‐day oral treatment with tamoxifen (0.22 mg/kg, q24h) or dexamethasone (0.06 mg/kg, q24h) on lung function, endoscopic tracheal mucus score and bronchoalveolar lavage fluid cytology were compared.ResultsTamoxifen significantly improved the pulmonary resistance (R L; mean reduction of 1.15 cm H2O/L/s [CI: 0.29‐2.01, P = .007] on day 13), but had no effect on the other variables evaluated. Dexamethasone normalized lung function (mean reduction of R L of 2.48 cm H2O/L/s [CI: 1.54‐3.43, P < .0001] on day 13), without affecting airway neutrophilia.Conclusions and Clinical ImportanceResults 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.

Background: Intra-articular (IA) administration of corticosteroids is performed routinely in equine practice. The lung function of severe asthmatic horses has recently been shown to be improved by IA triamcinolone acetonide (TA). We therefore hypothesised that IA methylprednisolone acetate (MPA), another commonly used corticosteroids, would also decrease the airway obstruction in severe asthmatic horses. Objectives: To compare the effects of intra-articular (IA) and intramuscular (IM) methylprednisolone acetate (MPA) administration on lung function and serum cortisol levels in horses with severe asthma. Study design: Randomised and controlled experiments on severe asthmatic research animals. Methods: Severe asthmatic horses in exacerbation were administered 200 mg of MPA either intramuscularly (n = 6) or via intra-articular injections in the tarsocrural joints (n = 6; 100 mg/joint). Serum cortisol concentration and pulmonary function was measured for 8 days. Results: A significant decrease in pulmonary resistance in the IA group (P = .003, mean diff 1.14) on day 1 in comparison with baseline was observed. A significant decrease from baseline was also observed on serum cortisol values in the IA group 6 hours after injection (P = .001, mean diff 44.5), and at day 1 (P = .003, mean diff 45.1). Main limitations: Joint health was not evaluated in the current study and the physiological response of the severe asthmatic horses might deviate from that of the milder forms of asthma. Conclusions: MPA IA administration improves the lung function of severe asthmatic horses. However, this effect was mild and of a short duration.

Summary Background Locally administered corticosteroids are commonly used to treat joint diseases in sport and racehorses. As they are also the most potent drugs for the treatment of equine asthma, we hypothesised that the intra‐articular corticosteroids used to treat joint diseases also improve the lung function in horses with severe asthma, thus potentially delaying the diagnosis of this common lung condition. Objectives To compare the effects of intra‐articular (IA) and intramuscular (IM) triamcinolone acetonide (TA) on lung function in horses with severe asthma. Study design Randomised and controlled experiment on asthma‐prone research animals. Methods Horses with severe asthma in clinical exacerbation were given either 20 mg of TA in both tarsocrural joints (n = 5; 40 mg/horse) or 40 mg of TA intramuscularly (n = 5). Lung function and TA serum concentrations were measured weekly for 35 days. TA serum concentrations were also evaluated on day 3. Results The pulmonary resistance (RL) and elastance (EL) values decreased by day 7 in the IA group (P<0.0001 and P = 0.003, respectively) and by day 14 in the IM group (P = 0.002 and 0.03, respectively). Lung function was improved up to days 21 and 28 in the IA and IM groups, respectively, when compared with baseline. TA serum levels were below the quantification limit (100 pg/ml) for 4 and 3 of the 5 horses in the IA and IM groups, respectively, on day 7. The area under the curve for RL, EL and the serum concentrations of TA were similar in both groups. Main limitations The response of horses with severe asthma might differ from that of high‐performance horses with mild/moderate asthma. Conclusions Intra‐articular administration of TA improves lung function in horses with severe asthma, an effect that persists when TA serum concentration is below the quantification level that is employed as a threshold by the International Association of Racing Commissioners.

Background: A study reported low systemic availability of injectable dexamethasone nebulized to healthy horses using the Flexineb mask. When used in horses with severe asthma and a different nebulizer, lack of efficacy and cortisol suppression were observed.Hypothesis: Nebulized dexamethasone is as effective as PO administration for the treatment of severe asthma in horses.Animals: Twelve horses with severe asthma from a research herd.Methods: Randomized clinical trial. Horses were divided into 2 groups and received 5 mg of dexamethasone sodium phosphate by nebulization using a Flexineb mask (NE, n = 6) or PO (OR, n = 6) q24h for 7 days. Lung function and serum cortisol concentrations were evaluated at baseline, after 4 days of treatment (D4) and 1 day after the last treatment (D8). Data were analyzed using linear mixed models with Benjamini-Hochberg adjustments.