Pharmacokinetics of thiopentone in the horse

Abstract

The pharmacokinetics of thiopentone sodium administered intravenously as a single dose (11 mg/kg) were studied in acepromazine pre-medicated horses and ponies in which anaesthesia was maintained with either halothane (Group 1) or isoflurane (Group 2). The results showed that the disposition kinetics of thiopentone in horses and ponies were best described by a three-compartment open model. In plasma, a very short initial distribution phase in both horses and ponies, half-life 1.4 +/- 1.2 min (mean +/- SD) and 1.3 +/- 0.7 min, respectively, was obtained, which was followed by a second comparatively slower redistribution phase, half-life 16 +/- 12 min and 11 +/- 5 min, respectively. The volume of distribution for the drug was large, especially in the ponies which received isoflurane (1127 +/- 86 ml/kg), compared to the horses which received halothane (742 +/- 89 ml/kg). The drug had a somewhat shorter elimination half-life in the horses (147 +/- 21 min) than in than ponies (222 +/- 44 min), but no obvious difference in clearance of the drug was observed between the horses (3.5 +/- 0.5 ml/min/kg) and ponies (3.6 +/- 0.8 ml/min/kg).

Changes in the EEG during castration in horses and ponies anaesthetized with halothane

“…The potential for thiopental to affect the EEG is clearly relevant, and in order to minimize its effects, the recording of baseline data did not commence until approximately 30 minutes after the induction of anaesthesia. The pharmacokinetics of thiopental given intravenously to horses anaesthetized with halothane have been studied (Abass et al. 1994), and Johnson et al.…”

Effect of acepromazine and butorphanol on halothane minimum alveolar concentration in ponies

“…(1977). Based on a previous study of thiopentone kinetics in horses (Abass et al 1994), it is estimated that the plasma thiopentone concentration was less than 2 pg/ml at the end of the 120 min equilibration period, and this would have decreased further by the time baseline MAC was determined. Thiopentone concentrations of this magnitude are unlikely to have a significant effect on halothane MAC (Stone eta/.…”

Influence of Bolus Injection of Thiopental Sodium on Respiratory and Cardiovascular Function under General Anesthesia in the Horse

“…Drug shows a 3-phase pharmacokinetic profile. The durations of the first phase and the second phase have been reported to be 2.8 and 48.7 min in humans [3]; they are 1.4 and 16 min in the horse [1]. In this study, the interval between the first and the second dose was 30 min.…”