Pharmacokinetics of midazolam after intravenous administration to horses

Abstract

Midazolam produces muscle relaxation but not sedation in adult horses.

Comparison of midazolam and diazepam as co-induction agents with ketamine for anaesthesia in sedated ponies undergoing field castration

“…Hubbell et al. () report a median t 1/2β for midazolam of 3.6 hours (range 2.0–4.1) after an IV dose of 0.05 mg kg −1 in conscious healthy horses. Muir et al.…”

Evaluation of the use of midazolam as a co‐induction agent with ketamine for anaesthesia in sedated ponies undergoing field castration

“…However, whilst benzodiazepines are routinely used in equine anaesthesia for these effects there are few studies demonstrating the benefits of including them in a ketamine-alpha-2 agonist induction protocol [8][9][10]. Ataxia and weakness secondary to muscle relaxation caused by benzodiazepines have also been reported by others [8,14,16,17], however no difference in recovery quality or degree of ataxia was observed in this study. Marntell and Nyman [9] reported that the use of diazepam improved muscle relaxation and these findings are consistent with this study and others [10].…”

“…The effects of benzodiazepines on muscle relaxation are well known [4] and have been demonstrated for midazolam in many domestic species [12][13][14][15]. The effects of benzodiazepines on muscle relaxation are well known [4] and have been demonstrated for midazolam in many domestic species [12][13][14][15].…”

“…Midazolam alone is not reported to produce sedation or anaesthesia in adult horses but causes agitation [14] and it would be expected that this would shorten, rather than lengthen the recovery period. The enhanced muscle relaxation afforded by midazolam may account for the reduced number of additional ketamine and detomidine injections required; however, it does not explain the increased time to first movement, sternal or standing positions.…”

Propofol with ketamine following sedation with xylazine for routine induction of general anaesthesia in horses

“…Potentially, the lack of midazolam or diazepam in these horses may have contributed to the speed and smoothness of recovery. Midazolam has a long half-life in horses; greater than 200 minutes at 0.05 mg/kg intravenous and greater than 400 minutes at 0.1 mg/kg intravenous (Hubbell and others 2013). Although there is limited pharmacokinetic reported for propofol in horses, the half-life of propofol when administered with ketamine is 69 minutes (Nolan and others 1996).…”