Effects of xylazine on airway function in ponies with recurrent airway obstruction

Richard V. Broadstone From the Pulmonary Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314.

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Peter R. Gray From the Pulmonary Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314.

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N. Edward Robinson From the Pulmonary Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314.

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Frederik J. Derksen From the Pulmonary Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824-1314.

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SUMMARY

The effect of iv administration of the α2-adrenoceptor agonist xylazine hydrochloride (0.5 mg/kg of body weight) was examined in ponies with recurrent obstructive pulmonary disease, commonly called heaves. Six ponies with the disease (principals) were studied during clinical remission and during an acute attack of airway obstruction precipitated by stabling and feeding of dusty hay. Six control ponies were also studied. In principal ponies with airway obstruction, xylazine administration significantly (P < 0.05) decreased pulmonary resistance and increased dynamic compliance, but did not affect Pao2 or Paco2. The α2-antagonist yohimbine blocked the pulmonary effects of xylazine. Administration of saline solution was without effect in both groups of ponies at all periods and xylazine did not have effect in controls or in principals in clinical remission.

SUMMARY

The effect of iv administration of the α2-adrenoceptor agonist xylazine hydrochloride (0.5 mg/kg of body weight) was examined in ponies with recurrent obstructive pulmonary disease, commonly called heaves. Six ponies with the disease (principals) were studied during clinical remission and during an acute attack of airway obstruction precipitated by stabling and feeding of dusty hay. Six control ponies were also studied. In principal ponies with airway obstruction, xylazine administration significantly (P < 0.05) decreased pulmonary resistance and increased dynamic compliance, but did not affect Pao2 or Paco2. The α2-antagonist yohimbine blocked the pulmonary effects of xylazine. Administration of saline solution was without effect in both groups of ponies at all periods and xylazine did not have effect in controls or in principals in clinical remission.

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