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 •
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