USE OF A HAND-HELD, METERED-DOSE AEROSOL DELIVERY DEVICE TO ADMINISTER PIRBUTEROL ACETATE TO HORSES WITH HEAVES

Aerosol administration of bronchodilators to horses is recommended for treatment of certain airway diseases such as 'heaves'. We have develo ped a novel, hand-held, metered-dose inhaler and we sought to determin e the bronchodilator efficacy of the beta(2) adrenoceptor agonist pirb uterol delivered by this device to horses affected with 'heaves', To i nduce airway obstruction, 6 heaves susceptible horses were stabled, be dded on straw and fed hay. When the maximum change in pleural pressure during tidal breathing (Delta Ppl(max)) was greater than 20 cmH(2)O o n 2 consecutive days, pulmonary function was measured before and 5, 10 and 30 min, as well as 1, 2, 3, 4, 5, 6 and 7 h after administration of aerosol pirbuterol. Pirbuterol was administered using a metered can ister and the hand-held delivery device that was inserted into the lef t nostril. Either vehicle or pirbuterol acetate (400, 600, 800, 1200 o r 1600 mu g) was administered to each horse. Relief of airway obstruct ion indicated by changes in pulmonary function was observed within 5 m in after administration of both vehicle and pirbuterol. Significant de creases in Delta Ppl(max) and pulmonary resistance (R(L)) and an incre ase in dynamic compliance (C-dyn) persisted for the 7 h duration of th e experiment. Comparison of the effect of vehicle and pirbuterol at ea ch time period showed that pirbuterol decreased R(L) and Delta Ppl(max ) significantly for up to 1 h. The optimal dose was determined to be 6 00 mu g. Immediate response to treatment, magnitude of drug effect and lack of side effects indicated that aerosol pirbuterol is an effectiv e and safe bronchodilator in horses with 'heaves', The hand-held, mete red-dose aerosol delivery device was very convenient and extremely eff ective and is, therefore, recommended for delivery of therapeutic aero sols to horses.