The metabolism of promazine and acetylpromazine in the horse.

This study analyzed the metabolism of promazine hydrochloride and acetylpromazine maleate, two drugs used in veterinary practices, when administered to horses. The researchers identified several metabolites resulting from the breakdown of these drugs in the equine body and found that their presence varied depending on whether promazine hydrochloride or acetylpromazine maleate had been administered.

Objective of the research

• The primary aim of this study was to gain a deeper understanding of how horses metabolize promazine hydrochloride and acetylpromazine maleate – two medications frequently used in veterinary medicine. The researchers sought to identify the various metabolites that result from the breakdown of these drugs in the horse’s body.

Methodology

• The researchers administered promazine hydrochloride and acetylpromazine maleate to horses intravenously at clinical dosage levels.
• Urine samples were collected from these horses and analysed to detect the parent drugs and their metabolites. Key methods used for this analysis included beta-glucuronidase/arylsulfatase hydrolysis, a biochemical process that breaks down certain organic substances.

Findings

• In the urine of horses given promazine hydrochloride, the researchers detected the parent drug along with four metabolites. The two major metabolites detected were 3-hydroxypromazine and 3-hydroxydesmonomethyl-promazine, both of which were present as conjugates and thus had to be identified after hydrolysis.
• Two minor metabolites –promazine N-oxide and promazine N-oxide sulfoxide – were also detected. Contrary to previous studies, promazine sulfoxide was not found to be the major nonconjugated metabolite at the administered dosage.
• For horses administered acetylpromazine maleate, three metabolites were found in their urine: 7-hydroxyacetylpromazine, 2-(1-hydroxyethyl)-7-hydroxypromazine, and 2-(1-hydroxyethyl)promazine sulfoxide. The first two were identified after hydrolysis.

Significance of the Research

• The results of this study contribute to the existing knowledge about how horses metabolize promazine hydrochloride and acetylpromazine maleate.
• The findings can aid future research and drug development by helping understand the processes and transformations these drugs undergo in the horse’s body after administration. It also helps to identify any potential bi-products that might have unforeseen implications on the horse’s health or performance.