Prediction of pharmacokinetic clearance and potential Drug-Drug interactions for omeprazole in the horse using in vitro systems.

This study investigates the ways that the drug omeprazole is metabolized in horses and how it may interact with another drug, chloramphenicol. Data indicates that analysis of omeprazole’s clearance using hepatocytes can predict potential drug-drug interactions.

Investigation on Omeprazole Metabolism

The research revolves around the study of omeprazole, a commonly used drug, its pharmacokinetics attributes in horses, and its possible interaction with another medication named chloramphenicol. The study makes use of:

• Isolated and preserved equine hepatocytes and hepatic microsomes, acquired from three horses.
• The “substrate depletion method” to ascertain the kinetics of omeprazole metabolism, such detecting values for V (Flow Rate), K (Elimination Rate Constant), and the Intrinsic Clearance (CL) of the drug alongside the measurement of K values for the formation of three metabolites.

Extrapolation to Hepatic Plasma Clearance

Once the metabolic analysis was complete, the study then extrapolated the obtained clearance (CL) figures to hepatic plasma clearance (also known as CL) using two models:

• Well-Stirred Model
• Parallel Tube Model

The research discovered that the accurate prediction of the clearance for omeprazole was possible through the use of fresh or preserved equine hepatocytes. However, hepatic microsomes provided a lower prediction.

Drug-Drug Interaction Study

In investigating the potential for drug-drug interaction (DDI) between omeprazole and chloramphenicol, the research used equine microsomes. Chloramphenicol served as an inhibitor in this study. The researchers arrived at an average inhibitor constant (K), assuming competitive inhibition, of 15.4 ± 5 µM.

Significance of the Research

This study marks the first successful report of drug clearance extrapolation in a horse using equine hepatocytes. More importantly, it also showcased the potential to predict Drug-Drug Interactions using microsomes. The results can inform further research and medical practices about omeprazole administration to horses and the possible implications it may have when co-administered along with other medications such as chloramphenicol.