Identification of some new clemastine metabolites in dog, horse, and human urine with liquid chromatography/tandem mass spectrometry.

The study aims to explore how the drug clemastine is metabolized (broken down) in the bodies of dogs, horses, and humans after administering a single dose. The researchers discovered new metabolites (products of metabolism) in the urine samples from these species, indicating variations in how clemastine is metabolized among different species.

Metabolism Study and Methodology

• The study specifically examines how clemastine, a drug usually prescribed to treat allergies, is metabolized in dogs, horses, and humans after receiving a single dose.
• The researchers collected urine from the subjects and performed two types of extraction methods: solid-phase extraction and liquid-liquid extraction.
• The extracted samples were then analyzed using liquid chromatography/tandem mass spectrometry to identify and categorize the unchanged drug and both phase I and II metabolites. Metabolites are substances that are created during the metabolism process.
• The identification of these metabolites was done based on their molecular mass and the interpretation of product ion spectra.

Findings and Conclusions

• Clemastine in its unchanged form was found in the urine samples of dogs and humans, but not in horses.
• In humans and dogs, a phase I metabolite, norclemastine, was identified. In all three species, metabolites with one and two additional oxygens were found. The oxygen location varied by species, indicating differences in metabolic pathways.
• Glucuronidated monohydroxyclemastine, a product of phase II metabolism, was found in human urine. In horse urine, both mono- and dihydroxyclemastine glucuronides were identified. However, these phase II metabolites were not present in dog urine.
• The researchers conclude that the study not only provides a new understanding of clemastine’s metabolic fate in dogs and horses (which hasn’t been extensively studied before) but also identifies new human metabolites of the drug.
• The discovery of new metabolites and the variation of metabolic pathways in different species increases our understanding of clemastine’s efficacy and potential side effects across these species.