A mass spectrometric study on meloxicam metabolism in horses and the fungus Cunninghamella elegans, and the relevance of this microbial system as a model of drug metabolism in the horse.

The research article presents a study exploring how the non-steroidal anti-inflammatory drug meloxicam is metabolized in horses and in the fungus Cunninghamella elegans, with aims to validate the utility of C. elegans as a model for this specific type of drug metabolism in horses.

Objective and Methodology

• The main objective of this study was to investigate the metabolic transformation of a non-steroidal anti-inflammatory drug, meloxicam, in both horses and the filamentous fungus Cunninghamella elegans.
• The metabolites created from this process were identified and then compared between horses and the fungus. The fungus was then used to generate larger quantities of these metabolites, to be utilized as reference material for future analyses.

Findings

• The findings of the study revealed that C. elegans served as a reliable model of Phase I meloxicam metabolism in horses since all four metabolites found were identical in both species. This suggests a similarity in drug metabolism between the fungal and horse systems in this context.
• Two main metabolites, 5′-hydroxymethylmeloxicam and 5′-carboxymeloxicam, were identified. Additionally, a second isomer of hydroxymeloxicam and dihydroxylated meloxicam were discovered for the first time in horse urine and the microbial incubations.
• The research found no Phase II metabolites in the C. elegans samples — but they did detect hydroxymeloxicam glucuronide in horse urine for the first time.
• Further analysis of urine from six horses showed that 5′-hydroxymethylmeloxicam was detected in higher intensity compared to the parent drug and other metabolites — and it remained detectable for up to 14 days after the last given dose in some horses.

Implications and Recommendations

• The authors of the study suggest that analytical methods used for the detection of meloxicam in horse urine (especially in cases of suspected prohibited use) should focus on the 5′-hydroxymethyl metabolite.
• They also proffer that C. elegans is a valid organism to produce large amounts of this metabolite, which may potentially be utilized as a reference compound in future studies.