EFFECT OF SODIUM CROMOGLYCATE ON LIGHT RACEHORSES WITH ELEVATED METACHROMATIC CELL NUMBERS ON BRONCHOALVEOLAR LAVAGE AND REDUCED EXERCISE TOLERANCE

Some young horses with clinical signs of small airway disease demonstr ate increased metachromatic cell numbers on bronchoalveolar lavage. Th e purpose of this study was to determine the effect of sodium cromogly cate treatment on clinical signs, bronchoalveolar lavage cytology and bronchoalveolar lavage histamine parameters in these horses. Twelve ra cehorses (age: 3.4 +/- 1.6 years) with a history of respiratory embarr assment at exercise, clinical signs of obstructive airway disease and bronchoalveolar lavage metachromatic cell differential greater than 2% were selected. Horses were randomly assigned to receive either 200 mg sodium cromoglycate or saline placebo nebulized twice daily for 7 day s. A clinical respiratory score was assigned and bronchoalveolar lavag e was performed on each animal on days 0 and 7. Measurements were made of the following bronchoalveolar lavage fluid parameters: total nucle ated cell concentration, differential cell percentage and concentratio n, supernatant and lysate histamine concentration, lysate: supernatant histamine ratio and metachromatic cell histamine content. Between the two evaluation periods, sodium cromoglycate treated horses demonstrat ed an improvement in respiratory score (P = 0.01) and a stabilizing of metachromatic cell histamine content (P = 0.04) when compared with pl acebo treated horses. We conclude that sodium cromoglycate is effectiv e for the treatment of small airway disease in this population of youn g racehorses although the pharmacodynamics of this drug in the horse r equire further investigation.