Exercise-Induced Arterial Hypoxemia in Thoroughbreds Is Not Affected by Administration of the H1 Histamine Receptor Antagonist Tripelennamine Hydrochloride

Exercise-induced arterial hypoxemia (EIAH) in human subjects may be associated with pulmonary injury/capillary stress failure-induced histamine release and is reported to be ameliorated by administration of H1 antihistiminics. EIAH is a routine occurrence in strenuously exercising Thoroughbreds, 75–100% of which also experience exercise-induced pulmonary hemorrhage (EIPH). In contrast with reports in human subjects, our data revealed that pre-exercise administration of intravenous tripelennamine hydrochloride (an H1 histamine receptor antagonist) had no affect on EIAH, desaturation of hemoglobin, hypercapnia, or acidosis. The failure of an intravenously administered H1 receptor antagonist to significantly modify EIAH suggests that pulmonary injury-induced histamine release may not play a major role in causing EIAH in Thoroughbred horses. Authors’ addresses: University of Illinois, College of Veterinary Medicine, Urbana, IL 61802. © 2002 AAEP.