Evaluation of the effect of ranitidine on gastroduodenal contractile activity and gastric emptying in horses.

The study investigates the impact of ranitidine, a medication commonly used to reduce stomach acid, on gastric emptying in horses. The researchers concluded that while ranitidine can increase stomach muscle activity in lab settings, it does not speed up gastric emptying in healthy horses, suggesting that it is not a viable treatment for this purpose.

Objective and Methodology

• The primary goal of the study was to see how ranitidine influences gastric emptying, which is the process of food and liquid leaving the stomach, in horses. Ranitidine is a type of drug often used for the treatment of acid reflux and gastric ulcers, and its impact on the muscle activities of the stomach and small intestine (duodenum) was the main focus of the study.
• Initially, the research was conducted in vitro (outside the body) using muscle strips from the stomach and small intestines of five horses. These strips were suspended and attached to isometric force transducers, instruments that measure muscle tension. Once the stable contractions were observed, ranitidine was introduced at incrementally higher concentrations, and the resulting muscle responses recorded and compared.
• In the next phase, the study was carried out in vivo (on living organisms) using a group of six horses. The horses participated in a crossover study where each horse experienced each treatment. A wash-out period of two weeks between treatments was implemented to avoid interference. Ranitidine or saline solution was administered intravenously, followed by the administration of acetaminophen mixed with water through a nasogastric tube to evaluate gastric emptying. The concentration of acetaminophen in their blood was monitored at various times over a three-hour period using liquid chromatography tandem mass spectrometry. Defecation frequency was also documented.

Results and Conclusion

• The primary finding from the in vitro part of the research was that ranitidine increased the contractile activity of the stomach’s smooth muscle at dosages of 10(-4) M. However, when the horses were administered ranitidine in vivo, the medication did not have a significant impact on the plasma acetaminophen concentration, which indicates the rate of gastric emptying.
• Defecation frequency, which can be influenced by changes in gastrointestinal motility, did not differ between horses given ranitidine and those given a saline solution.
• Therefore, the researchers concluded that while ranitidine can provoke stomach muscle activity when tested in a lab, it doesn’t accelerate gastric emptying in healthy horses in a real-world context. Results suggest that ranitidine may not be instrumental in promoting gastric emptying.