Effects of single intravenously administered doses of omeprazole and ranitidine on intragastric pH and plasma gastrin concentration in nonfed ponies.

The research paper delves into a study conducted on ponies to understand the effects of omeprazole and ranitidine, both drugs commonly used to inhibit stomach acid, when administered intravenously. The study monitors changes in gastric pH levels and plasma gastrin concentration; it also observes any pattern of dose-dependency and the pharmacokinetics of intravenously administered omeprazole.

Study Design and Methodology

• Researchers used four Welsh mountain-type ponies as subjects for their study. These ponies were investigated under different circumstances; some received various intravenous doses of omeprazole (ranging from 0.125 to 2.0 mg/kg of body weight), while others were given ranitidine intravenously at a dose of 1.0 mg/kg.
• An indwelling electrode was employed to measure and monitor gastric pH levels.
• Pharmacokinetic variables of intravenous omeprazole administration were observed and recorded using the “two-compartment” model. In simple terms, pharmacokinetics is the study of how a drug is absorbed, distributed, metabolized, and eventually eliminated by the body.

Findings and Outcomes

• The study identified an observable, dose-dependent increase in mean gastric pH over 11 hours following the administration of omeprazole. This suggests that omeprazole might have an acid-suppressant effect, which increases as the drug dosage gets higher.
• Instances of high basal gastric pH sometimes obscured the effect of acid suppression on intragastric pH, making observations less clear-cut. Basal gastric pH refers to the stomach’s pH when it’s at rest, that is, when not engaged in digestion.
• A meaningful correlation could be established between plasma gastrin concentration and gastric pH during the course of acid-suppressant treatment, showing a probable relationship between these two variables. Gastrin is a hormone that promotes the production of gastric acid.
• The investigators revealed that intravenous omeprazole followed two-compartment pharmacokinetics. They also deduced the presence of saturable steps in the drug’s redistribution and elimination phases, hinting at a possible limit to the body’s ability to process the drug.

Conclusions and Future Work

• The researchers concluded that omeprazole could be a suitable alternative treatment for acid suppression in horses. Notably, a dose of 0.25 mg/kg seemed to induce approximately half-maximal inhibition of basal gastric pH in the ponies during the study.
• While these findings are promising, further research work was recommended to connect the dose-dependent effects revealed in this study to specific acid suppression targets in real clinical cases.