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Summary

Pulmonary function measurements were made in control ponies and in ponies with recurrent obstructive pulmonary disease (principals) during clinical remission and during an attack of acute airway obstruction. The ponies were given β-adrenergic antagonists and agonists to determine the role of β receptors in recurrent obstructive pulmonary disease, and to determine the subtypes of β receptors mediating bronchodilation in ponies. Aerosol administration of the β antagonists, propranolol (β1 and β2), atenolol (β1), and butoxamine (β2) decreased dynamic compliance (Cdyn) and increased pulmonary resistance (RL) in the principal ponies during airway obstruction, but were without effect when the ponies were in clinical remission. Intravenous administration of atropine reversed the effect of atenolol on Cdyn and RL, but was without effect on the decrease in Cdyn and increase in RL observed after butoxamine administration. The β antagonists did not affect airway function in the control ponies. The effect of β blockade on Cdyn and RL suggests β-adrenergic activation in the central and peripheral airways of principal ponies, mediated through both β2- and β1-adrenergic receptors. The aerosol β agonists, isoproterenol (β1 and β2), and clenbuterol (β2) attenuated histamine-induced airway obstruction to a similar extent in control ponies that were given histamine iv. In addition, the β1 antagonist, atenolol, did not attenuate the bronchodilation observed with isoproterenol. We concluded that, although β1- and β2-adrenergic receptors exist in pony airways and are activated during acute airway obstruction, bronchodilation in response to β agonists in ponies seems to be mediated primarily by β2-adrenergic receptors.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the dose of aerosolized albuterol sulfate required to cause bronchodilation in horses with recurrent airway obstruction (RAO) and duration of this effect.

Animals

19 horses with RAO (10 in experiment 1; 9 in experiment 2).

Procedure

Horses were moved from pasture to stables, and airway obstruction was induced. Pulmonary function was measured in 10 horses before and 5, 10, and 30 minutes after administration of vehicle or 120, 240, 360, or 720 µg of the drug. Nine horses received vehicle or 360 or 720 µg of albuterol, and pulmonary function was measured at baseline and 5 minutes and 1, 2, 3, 4, 5, 6, and 7 hours later. Horses were evaluated for adverse drug effects.

Results

360 µg of albuterol was required to cause significant bronchodilatation; 720 µg did not enhance bronchodilatation or increase duration of action. Depending on which pulmonary function parameter was evaluated, bronchodilatation achieved by use of albuterol lasted between 30 minutes and 1 hour. Because there was a significant vehicle effect, the combined effect of vehicle and drug lasted up to 3 hours. Adverse effects were not observed.

Conclusions

Aerosolized albuterol, 360 or 720 µg, is a safe and effective bronchodilator in horses with RAO. Onset of action is rapid (5 minutes), and effects last from 30 minutes to 3 hours.

Clinical Relevance

Aerosolized albuterol is useful for treatment of bronchospasm in horses with RAO. (Am J Vet Res 1999;60:689–693)

Free access
in American Journal of Veterinary Research