Influence of respiratory tract disease and mode of inhalation on detectability of budesonide in equine urine and plasma.

The research article focuses on studying the impact of respiratory tract disease, specifically recurrent airway obstruction (RAO), and the method of inhaling on the detectability of the drug budesonide in horse plasma and urine samples. The objective is to gain insights to help in extending the time gap between the administration of the drug and participation in sports events, particularly for horses with respiratory diseases.

Study Design

• The study involved 16 horses divided into two groups – 8 healthy control horses, and 8 horses affected by RAO. The condition of the horses was assessed based on clinical examination, blood gas analysis, bronchoscopy, and cytologic examination of bronchoalveolar lavage fluid.
• The researchers administered budesonide (3 μg/kg) twice daily for 10 days to 4 horses from each group while they were at rest. The remaining 4 horses from each group inhaled budesonide during lunging exercise.
• Plasma and urine samples were subsequently collected within the window of 4 to 96 hours post inhalation and were tested for the presence of budesonide. Additionally, the urine samples were examined for the metabolites 6β-hydroxybudesonide and 16α-hydroxyprednisolone.

Results

• Findings indicated that the budesonide concentrations were significantly higher at all-time points for horses affected by RAO, in comparison with healthy horses.
• All samples from the RAO-affected horses had budesonide concentrations above the limit of detection at 96 hours after inhalation, whereas this was true for only 2 of the control horses.
• The detected concentrations of budesonide were also higher in horses that inhaled the drug during exercise, compared with horses that inhaled it at rest. However, this difference was not significant.

Conclusions and Clinical Relevance

• Based on the results, the study suggests that the time interval between the inhalation of a glucocorticoid and participation in sporting events should be increased. This recommendation particularly holds when the inhalation treatment is administered during exercise to horses affected by respiratory tract disease.