Colon constipation in horses after sustained-release buprenorphine administration.

This study explores the effects and side effects of sustained-release buprenorphine, a pain medication, in horses. The research found that while this method ensured the presence of the drug in the body for at least 48 hours, it led to serious side effects, including colon constipation and increased movement, making its clinical use undesirable.

Research Methodology

• The study was a pilot trial involving four horses aged 18 to 27 years and weighing between 508 and 578 kilograms.
• The researchers administered a solution of buprenorphine, mixed with a sustained-release drug carrier, to the horses either subcutaneously (under the skin) or intramuscularly (into the muscle).
• Throughout the experiment, the horses were closely monitored, and their steps were counted. Blood samples were also collected to measure the concentration of buprenorphine in plasma.

Results

• The study found that all four horses developed constipation that required medical intervention, and there was an increase in their locomotor activity.
• One horse had to be euthanized during recovery due to weakness and severe obstruction in its lower airways after undergoing surgical treatment for constipation.
• The remainder of the horses fully recovered within 5 to 7 days.
• The presence of buprenorphine in plasma was maintained for roughly 48 hours, with concentrations ranging between 1 and 8 ng/mL.
• No local reactions were observed at the injection sites.

Conclusions

• While the administration of a sustained-release formulation of buprenorphine ensured a plasma concentration compatible with its pain-relieving properties for at least 48 hours, the route led to severe undesirable effects, making it unsuitable for clinical use.
• The severe side effects observed were colon constipation and a substantial increase in movement.