Pharmacokinetics and bioequivalence testing of five commercial formulations of omeprazole in the horse.

The research article investigates the relative pharmacokinetics of five different commercially available versions of the drug omeprazole, commonly employed to treat gastric ulcers in horses, and tests their bioequivalence using one formulation as a reference standard.

Objective and Approach

• The study aimed at understanding and comparing the pharmacokinetics – how a drug is absorbed, distributed, metabolised, and eliminated by the body – of five popular commercial preparations of omeprazole. The secondary goal was to verify if any of the four formulations showed bioequivalence that is their biological equivalent effectiveness when administered in the same dosage as the reference standard formulation.
• The research included twelve mature Thoroughbred horses which were fasted for 16 hours and then administered with 2 grams of each omeprazole formulation in a cross-over design – a type of longitudinal study where subjects are randomly allocated to a sequence of two or more treatments given consecutively.

Methods and Techniques

• The researchers collected blood samples at regular intervals post administration and determined the plasma omeprazole concentration using a detection technique called Ultra High-Performance Liquid Chromatography-Mass Spectrometry (UHPLC-MS).

Results

• No significant differences were detected between three out of the four formulations and the reference standard based on their respective pharmacokinetics. This indicates equivalent drug absorption, distribution, metabolisation, and elimination patterns as compared with the standard reference.
• However, the fourth formulation did exhibit dissimilar pharmacokinetics with a lower peak concentration (Cmax) and longer time to reach peak concentration (Tmax) in comparison with the reference formulation.

Conclusions

• Despite the pharmacokinetic similarities across three formulations, none of the formulations tested were confirmed as bioequivalent to the reference. This essentially means that none of these had a similarly effective biological response in the living organism like the reference formulation.
• The researchers also concluded that the method of protection utilised by different formulations of omeprazole (enteric-coated granules vs. buffering) does not significantly alter the pharmacokinetics of the drug. In other words, the physical form of the drug does not seem to impact its absorption and action within the body.
• Further research is needed to establish bioequivalence before making direct comparisons between different formulations.