Influence of laxatives on gastric emptying in healthy Warmblood horses evaluated with the D-xylose absorption test.

The use of laxatives is crucial in the treatment of horses with large colon impaction. To reach the impacted mass, the laxative must leave the stomach and pass through the small intestine. The aim of this study was to determine whether the most frequently used saline and lubricant laxatives influence gastric emptying. Six fasted normal adult Warmblood horses were used in a randomized study design with five laxative trials (1.8% sodium sulfate [1.8% Na2SO4], 4.2% magnesium sulfate [4.2% MgSO4], mineral oil [MOil], 25% sodium sulfate [25% Na2SO4], 25% magnesium sulfate [25% MgSO4]) and two trials with water (at either 20 ml/kg BW [Water 20] or 4 ml/kg BW [Water 4]), administered via nasogastric intubation. For indirect measurement of liquid-phase gastric emptying, a liquid passage marker (0.5 g D-xylose/kg BW as 10% solution) was added to each trial. Serum samples were collected at pre-determined time points for pharmacokinetic analysis. The time to reach maximum serum concentration (T(max)) was considered as gastric emptying rate. Significant differences were detected for T(max) of 4.2% MgSO4 compared to Water 20 and for T(max), the maximum serum concentration (C(max)) and the area under the curve determined up to 90 min (AUC90) of 25% Na2SO4 and 25% MgSO4 compared to Water 4. Neither 1.8% Na2SO4, nor MOil delayed gastric emptying rate compared to water (Water 20, Water 4, respectively). 4.2% MgSO4 as well as 25% Na2SO4 and 25% MgSO4 significantly delayed gastric emptying rate in comparison to water (Water 20, Water 4, respectively).