Equine Health Update EHU Vol 19 Issue 3 - Page 15

EQUINE | Abstracts Bioavailability and tolerability of nebulised dexamethasone sodium phosphate in adult horses Short title: Nebulised dexamethasone in equine asthma Injectable dexamethasone may be a cost-effective al- ternative to other inhaled corticosteroids for long-term management of equine asthma. This randomised cross- over study set out to determine the bioavailability of injectable dexamethasone when inhaled via a nebuliser device. Dexamethasone was administered at 5 mg once daily for 5 days either intravenously or via a nebuliser in a random cross-over design, with a 3-week washout period between each administration in six healthy sta- bled horses. Plasma concentrations of dexamethasone was measured by liquid chromatography from samples before and at serial intervals up to 24 h after dexametha- sone administration. ACTH stimulation tests were per- formed before the first dose and before the last dose. Bronchoalveolar lavage (BAL) was performed before the first dose and 2 hours after the last dose to provide samples for cytology. The mean bioavailability of nebu- lised dexamethasone was 4.3%. When dexamethasone was administer intravenously, a significant reduction in basal cortisol concentration was observed from Day 1 to Day 5. When the nebulised route was used there was no significant change in cortisol concentration, indicating low systemic bioavailability. For both routes of administration, the percentage of neutrophils in BAL fluid decreased significantly likely to be due to the anti- inflammatory effects of dexamethasone on the airways. Bottom line: Dexamethasone administered via a nebu- liser has minimal systemic bioavailability and appears to reduce lower airway inflammation, therefore may pro- vide a safe and cost-effective long- term treatment for equine asthma. Additional studies are required before it can be recommended for clinical use. • Volume 19 no 3 • September 2017 • 15