Modulation of bronchial responsiveness in horses by phenylbutazone and furosemide.

The research article discusses the effects of two drugs, phenylbutazone and furosemide, on the bronchial responsiveness in horses. It found that while furosemide creates changes in pulmonary function, it is phenylbutazone that provides a significant protective effect against changes induced by histamine.

Objective and Design of Study

• The aim of this study was to evaluate the impact of two drugs, phenylbutazone (PBZ) and furosemide (FUR), on the respiratory system of horses, with a specific focus on bronchial responsiveness.
• The study involved four healthy Thoroughbreds, with data analysed using a Latin square design, a popular method in scientific research to eliminate any two-way influence of variables. In this case, it helped the authors control the effects of separate drug treatments.
• Four groups were formed for histamine provocation tests: one group received no prior treatment of PBZ or FUR, one was given PBZ 30 minutes prior, one was given FUR an hour prior, and one was given a combination of PBZ and FUR.

Pulmonary Function Tests

• The researchers monitored the horses’ lung function through a variety of measurements: dynamic compliance (lung’s ability to expand), resistance, respiratory frequency (rate of respiration), tidal volume (amount of air displaced during inhalation and exhalation), and heart rate.
• This was done throughout the experiments to parse out the effects of the medications on different respiratory parameters.

Results

• The results indicated that phenylbutazone did not affect the basal pulmonary function, i.e., it did not change the standard parameters of the horses’ respiratory system.
• Contrarily, furosemide resulted in a significant increase in dynamic compliance and decrease in resistance, suggesting a positive effect on the horses’ lung function.
• When histamine was infused, it led to a decreased dynamic compliance and increase in resistance, respiratory frequency, and heart rate, showing that histamine adversely affected the normal lung functioning.
• Interestingly, the administration of phenylbutazone significantly reduced most of the negative changes induced by histamine, indicating the drug’s protective function against histamine response. Furosemide, however, was less effective at attenuating these harmful respiratory changes.
• Administering a combination of PBZ and FUR resulted in less effective results than using PBZ alone, which could suggest an interference or attenuating effect when both drugs are used simultaneously.