Bronchodilator activity of the selective muscarinic antagonist revatropate in horses with heaves.

The study explores the efficacy of a bronchodilator named revatropate, a selective muscarinic antagonist, in treating airway obstruction in horses suffering from heaves (also known as recurrent airway obstruction). The research demonstrated that both revatropate and another drug, ipratropium bromide, improved airway function quickly, and did not have significant side effects. However, revatropate was shown to significantly decrease the effort of breathing, as measured by clinical scores.

Study Design and Methodology

• Two protocols were used in this study. Protocol 1 was a blinded dose escalation test, which checked the reactions to different dosages of revatropate (1, 2, and 7 mg) and ipratropium bromide (0.3, 0.7, and 2mg). A negative control of inhaled saline was also included. Six horses with heaves were used for this part of the study.
• Protocol 2 used a cross-over design to compare the duration of the action of inhaled revatropate (1mg), ipratropium (0.3mg), and saline. This sought to assess how long the drugs continued to exert their effects after administration.

Findings of the Study

• The lowest doses of revatropate and ipratropium induced a swift and significant improvement in airway function within an hour.
• The efficacy of both revatropate and ipratropium were similar when it came to improving airway function. There was no significant difference found in their effectiveness.
• The highest doses of both drugs did not significantly affect the gastrointestinal sound score or iris function. They also led to dry mucous membranes and reduced gastrointestinal sound score in some horses.
• Revatropate was found to significantly improve clinical scores of breathing effort, improving the combined clinical score in the first hour and abdominal score in the initial 1-3 hours. These implications are noteworthy in the context of the ease of breathing for horses.
• No significant adverse events were observed in Protocol 2, although some horses had reduced gastrointestinal sound scores.

Conclusion

• Based on these results, the study concluded that revatropate can be used as a safe and effective bronchodilator to treat airway obstruction in horses suffering from heaves.
• It was also implied that while both drugs were generically similar in efficacy, revatropate showed distinctive advantages when it came to reducing the breathing effort, and had insignificant side effects.