Influence of laxatives on gastric emptying in healthy warmblood horses evaluated with the acetaminophen absorption test.

The study explores how different solutions of laxatives impact the rate at which food leaves the stomach in horses. The findings suggest that hypertonic saline solutions significantly slow down this process, whereas isotonic solutions have no significant impact.

Study Design and Method

• The study was conducted on six healthy, adult Warmblood horses that had been fasted.
• The horses were administered different solutions through nasogastric intubation. These solutions included 1.8% sodium sulfate, 4.2% magnesium sulfate, 25% sodium sulfate, 25% magnesium sulfate, and water at volumes of 20 ml/kg body weight or 4 ml/kg body weight.
• Each administered solution included acetaminophen (at a dosage of 20 mg/kg body weight in 200 ml of water). This was used as a liquid phase passage marker, a substance used to monitor the movement of other substances through the body.
• The researchers took serum samples at predetermined intervals of time for pharmacokinetic analysis, a method that studies how drugs move through the body.

Measurement and Findings

• The research used a variable called Tmax, the time it takes to reach maximum serum concentration, as a measure of the gastric emptying rate.
• When compared to the 4 ml/kg water control group, both the 25% sodium sulfate and the 25% magnesium sulfate solutions reached Tmax significantly later. This implies a slower gastric emptying rate.
• Moreover, the maximum concentration of acetaminophen (Cmax) in the serum was significantly lower in these two groups, and the area under the curve up to 90 minutes (AUC90) was also smaller, indicating a delay in gastric emptying rate.
• Contrarily, the isotonic solutions (1.8% sodium sulfate and 4.2% magnesium sulfate) did not have a notable influence on the gastric emptying rate.

Conclusion

• The study concluded that hypertonic solutions of saline laxatives (25% sodium sulfate and 25% magnesium sulfate) caused a significant delay in the gastric emptying rate, which could be a potential hardship when dealing with horses suffering from colon impaction. In contrast, isotonic solutions (1.8% sodium sulfate and 4.2% magnesium sulfate) did not show such detrimental effects.