Pharmacokinetics of intravenous and intramuscular buprenorphine in the horse.

The research investigates how buprenorphine, a pain-relieving drug, functions in horses when administered intravenously and intramuscularly. The study details the drug’s behavior in terms of clearance speed, half-life, distribution volume, and potential side effects such as excitement and gastrointestinal stasis.

Objectives and Methodology of the Study

• The primary objective of this study was to understand the pharmacokinetics, which is how the body processes a drug, of buprenorphine when administered to horses via two routes- intravenously and intramuscularly.
• The study was carried out on six horses using a randomized, crossover design. Each horse received buprenorphine administered intravenously (i.v.) and intramuscularly (i.m.) at a dosage of 0.005mg/kg.
• To observe the effectiveness and reaction of the horses to the drug, plasma samples were collected at predetermined times and they were closely observed for any possible adverse reactions.
• The drug concentration in the plasma samples was measured using a high-precision method known as ultra-performance liquid chromatography with electrospray ionization mass spectrometry.

Results of the Study

• The study determined the clearance rate of buprenorphine following intravenous administration as 7.97±5.16 mL/kg/min. The half-life, which is the time taken for the drug’s concentration to reduce to half its initial value, is measured to be 3.58 h (harmonic mean).
• The volume of drug distribution in the horse body following intravenous administration was estimated as 3.01±1.69 L/kg.
• The maximum concentration of the drug following intramuscular administration (C(max)) was considerably lower than the highest measured concentration after intravenous administration.
• The time taken to reach the maximum concentration (C(max)) and the half-life of the drug were found to be 0.9±0.69 h and 4.24 h, respectively, after intramuscular administration. The bioavailability, which defines how much of the drug reaches the system and becomes available at the site of action, varied between 51 to 88 percent.

Observations and Conclusions

• Some horses exhibited signs of excitement as a side effect of the drug administration. Gut sounds, indicating digestive activity, decreased in both groups of horses after several hours of drug administration, suggesting a possible experience of gastrointestinal stasis or inactivity.
• The study concludes that buprenorphine has a moderate half-life in horses and is found at concentrations that are anticipated to be therapeutic in other species, following both intravenous and intramuscular administration of 0.005mg/kg.
• It is important to be attentive to signs of excitement and gastrointestinal stasis, which may occur as a result of buprenorphine use in horses.