Use of midazolam in combination with medetomidine for premedication in healthy dogs.

Objective: To assess the sedative effects, propofol sparing properties and impact on quality of induction and intubation of intravenous (IV) medetomidine and midazolam administered consecutively at different doses compared to medetomidine alone in healthy dogs for premedication.

Study Design: Prospective, randomized, blinded, clinical study.

Animals: A total of 40 adult healthy client owned dogs, weighing 18 ± 7 kg (mean ± standard deviation).

Methods: Dogs were assigned to four groups: medetomidine 15 μg kg (positive control group), medetomidine 10 μg kg and midazolam 0.2 mg kg, medetomidine 5 μg kg and midazolam 0.3 mg kg, and medetomidine 5 μg kg and midazolam 0.2 μg kg. The same clinician assessed sedation after administration at T2.5 minutes and T5 minutes using a composite simple descriptive sedation scale ranging between 0 and 15 (0 = no sedation; 15 = profound sedation). The dose of propofol for induction, quality of induction, ease of intubation and any adverse events were recorded.

Results: There was no significant difference in sedation scores between treatment groups at T2.5 minutes or T5 minutes (p = 0.82 and p = 0.63, respectively). Administration of midazolam in combination with medetomidine resulted in 71% of dogs displaying paradoxical behaviours (p < 0.0001) such as agitation, excitation, restlessness, aggression and vocalization, which was different from pre-sedation. Propofol requirement was not different between groups. Induction and tracheal intubation quality was smooth in all groups.

Conclusion: In healthy dogs, at the doses studied, the combination of medetomidine-midazolam administered IV for premedication provided moderate sedation but was associated with a high incidence of paradoxical behaviours. This drug combination IV is not recommended for premedication in healthy dogs.