Effects of epidural morphine on gastrointestinal transit in unmedicated horses.

This research investigates how epidural morphine affects the gastrointestinal motility in healthy adult horses. The study concluded that while epidural morphine reduced gastrointestinal activity, it did not result in any symptoms of colic or ileus.

Research Methods

• The study was designed as a randomly ordered crossover experiment involving six healthy adult horses. Each horse was given either an injection of 0.2 mg kg(-1) of morphine or an equal volume of saline into their first intercoccygeal space (base of the spine) in a random sequence.
• The horses were kept in stables and fed a standardized diet with water provided as needed throughout the study.
• Observations included heart rate, respiratory rate, gastrointestinal sounds, behavior scores, and the presence of radiopaque spheres which were administered through a stomach tube to track gastrointestinal transit.
• Measurements were done before the drug administration and then at several intervals after the epidural injection, for a total duration of six days.
• Researchers used a mixed-effect model for data analysis, and the findings between the two treatment groups were compared.

Research Findings

• The results showed no significant differences between the morphine and saline treatments in terms of heart rate, respiratory rate, GI sounds, behavior score, or the total number of radiopaque spheres detected.
• However, the concentration of spheres per kg of feces was significantly lower in the morphine group at 18 and 24 hours post-injection, indicating slowed GI transit.
• On average, transit time after saline injection was 38 hours, while it was 43 hours after morphine injection. Additionally, the weight of feces per hour was significantly lower in the morphine group at only 4 and 8 hours after treatment.

Research Conclusions

• Based on the findings, the researchers concluded that epidural morphine at a dose of 0.2 mg kg(-1) reduced GI motility temporarily. However, it did not result in severe gastrointestinal problems such as ileus or colic in the studied horses.
• Though the findings provide valuable insight into the effect of epidural morphine on horses’ digestive systems, the researchers warn care should be taken when extrapolating these data to other situations considering other factors may likewise impact GI motility.