315 ICRAV 2026 POSTER SESSION 1. Merieux NutriSciences, Burnaby, BC, Canada 2. St. Paul’s Hospital, Vancouver, Canada 3. Canadian Pari-Mutuel Agency Research & Reference Laboratory, Ottawa, Canada ABSTRACT Dembrexine, also known as 2,4-Dibromo-6-{[(4-hydroxycyclohexyl)amino]methyl} phenol, is a highly regarded secretolytic agent commonly used in the treatment of respiratory conditions in horses, including equine asthma. Its effectiveness has been well-documented in laboratory animals, where it has shown a significant expectorant effect, a secondary antitussive action, and an increase in lung compliance. These properties make dembrexine an invaluable veterinary drug in managing respiratory diseases in equines, providing relief and improving their overall respiratory function. Sputolysin® is an oral formulation powder containing 5 mg/g of the active ingredient dembrexine hydrochloride monohydrate. It is specifically indicated for the symptomatic treatment of acute, sub-acute, and chronic respiratory diseases affecting both the upper and lower respiratory tracts, particularly in cases where there is an abnormal amount of mucus with increased viscosity. The purpose of this study was to examine the elimination profiles of dembrexine and its primary metabolite, cis-dembrexine, in horses. The investigation involved administering a regimen dose of Sputolysin® to four Standardbred mares. Plasma and urine samples were collected for up to 96 hours following the final administration. To achieve accurate quantification of dembrexine in the post-administration samples, a sensitive HPLC/MS/MS method was developed and validated. Dembrexine and cis-dembrexine were extracted from plasma samples using liquidliquid extraction at pH 9. Similarly, these compounds were recovered from urine samples following enzyme hydrolysis. Furthermore, the analysis of selected postdose urine samples, without enzyme hydrolysis, revealed the presence of multiple glucuronide metabolites. The detailed analytical methodology and the comprehensive results of the administration study will be described and discussed. Geoffrey Lam1, Devan Loganathan1, Rong Yi2, Michael Ryan3 Simultaneous Detection and Determination of Elimination Profiles of Dembrexine and its Major Metabolite in Horse Plasma and Urine After a Regimen Oral (PO) Administration of Dembrexine (Sputolysin Powder®)
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