Efficacy of oral and intravenous dexamethasone in horses with recurrent airway obstruction.

This study examines the effectiveness, onset, and duration of dexamethasone, administered both orally and intravenously, in treating horses with recurrent airway obstruction (RAO). It suggests that dexamethasone administered intravenously acts rapidly, while its oral administration to fasted horses also proves effective and tends to last longer.

Research Objective and Methods

• The researchers aimed to document the onset time and duration of effect of dexamethasone given through intravenous (IV) injection or orally, combined with fasting or not. The effectiveness of dexamethasone as treatment for recurrent airway obstruction (RAO) in horses is already established, but these variables were previously unknown.
• The study employed two protocols using RAO-affected horses with airway obstruction, testing both the effects of IV administration of dexamethasone versus saline solution, and comparing oral administration with various doses of dexamethasone with or without prior fasting. The duration and drying effect of the administered medication was tracked over specific periods of time.

Research Findings

• The study found that intravenously administered dexamethasone showed notable improvements in lung function within two hours, with maximum effect appearing 4-6 hours after administration.
• Orally administered dexamethasone was effective after six hours with the peak effect at 24 hours, when given a dose of 0.164 mg/kg body weight (bwt) before feeding. Additionally, it tended to have a longer-lasting effect when given orally, significantly affecting for up to 30 hours compared to saline.
• The research also found that fasting horses before oral administration of dexamethasone improved the treatment effectiveness. The results suggest that feeding decreases the bioavailability of dexamethasone, pointing out that fed horses showed similar effects to fasted horses when given a lower oral dose.

Conclusions

• The study concludes that intravenous administration of dexamethasone provides a quicker-onset treatment for horses affected by RAO. Simultaneously, oral administration to fasted horses was found to have a similarly effective, but longer-lasting effect.
• These findings are beneficial as they provide more options for administering dexamethasone to horses, which could be helpful if a rapid response is needed, or if a longer-lasting effect is desired. They also propose that fasting horses prior to oral medication could enhance the treatment’s efficacy.