Nebulisation of dexamethasone sodium phosphate for the treatment of severe asthmatic horses.
Authors: Mainguy-Seers S, Bessonnat A, Picotte K, Lavoie J-P
Journal: Equine veterinary journal
Summary
# Nebulised dexamethasone for severe equine asthma: limited efficacy in clinical practice Inhaled corticosteroids represent a mainstay therapy for equine asthma, yet cost remains a significant barrier to widespread adoption; previous work suggested that nebulised injectable dexamethasone might offer a cost-effective alternative with minimal systemic absorption in healthy horses. Mainguy-Seers and colleagues conducted a randomised, blinded trial comparing 5 mg dexamethasone sodium phosphate administered via nebulisation against oral administration in twelve horses presenting with severe asthmatic exacerbations, measuring pulmonary mechanics, clinical respiratory scores and serum cortisol at baseline, day 4 and day 8 of treatment. Contrary to expectations, the oral group showed significantly greater improvements in pulmonary resistance (mean reduction 1 cm H₂O/L/s, P=0.003) and clinical respiratory scores from day 5 onwards, whilst the nebulised group demonstrated no meaningful functional gains; notably, all horses retained residual bronchospasm on day 8 despite treatment, and both groups showed hypothalamic-pituitary-adrenal suppression. These findings suggest that nebulising an injectable corticosteroid formulation does not deliver the therapeutic benefit of conventional oral dosing for severe cases and carries the additional risk of systemic immunosuppression without proportionate pulmonary benefit—a distinction worth bearing in mind when discussing treatment options and cost considerations with equine practitioners managing refractory asthma.
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Practical Takeaways
- •Nebulisation of injectable dexamethasone at 5 mg daily is not recommended for severe equine asthma; oral administration was more effective in this trial
- •Despite theoretical advantages of inhaled corticosteroids, this injectable formulation failed to improve lung function measures in severe asthmatic horses
- •Both treatment routes caused systemic HPA suppression, suggesting careful monitoring is needed if pursuing either route clinically
Key Findings
- •Oral dexamethasone significantly improved pulmonary resistance by mean 1 cm H2O/L/s on day 8, while nebulised dexamethasone showed no improvement (P=0.003)
- •Respiratory clinical score was significantly reduced in the oral group from day 5 to day 8, but not in the nebulised group
- •All horses retained residual bronchospasm at study end despite both treatment routes
- •Both groups showed hypothalamic-pituitary-adrenal axis suppression with decreased serum cortisol concentrations