Effects of intramuscular and intranasal administration of midazolam–dexmedetomidine on sedation and some cardiopulmonary variables in New Zealand White rabbits

To compare the sedative and cardiopulmonary effects of intranasal (IN) and intramuscular (IM) administration of dexmedetomidine and midazolam combination in New Zealand White rabbits. A randomized, crossover experimental study. A total of eight healthy New Zealand White rabbits, aged 6–12 months, weighing 3.1 ± 0.3 kg (mean ± standard deviation). The animals were randomly assigned to administration of dexmedetomidine (0.1 mg kg–1) with midazolam (2 mg kg–1) by either IN or IM route separated by 2 weeks. The electrocardiogram, pulse rate (PR), peripheral haemoglobin oxygen saturation (SpO2), mean noninvasive arterial pressure (MAP), respiratory frequency (fR) and rectal temperature were measured before drug administration (baseline), T0 (onset of sedation) and at 5 minute intervals until recovery. The onset of sedation, duration of sedation and sedation score (SS) were also recorded. The PR was significantly lower in treatment IM than in treatment IN over time (p = 0.027). MAP < 60 mmHg developed in two and four rabbits in treatments IN and IM, respectively. SpO2 progressively decreased over time in both treatments. fR was lower than baseline at several time points in both treatments. Onset of sedation was shorter in treatment IN (90 ± 21 seconds) than in treatment IM (300 ± 68 seconds) (p = 0.036). Duration of sedation was longer in treatment IM (55.2 ± 8.7 minutes) than in treatment IN (39.6 ± 2.1 minutes) (p = 0.047). No significant difference in SS was observed between treatments (p > 0.05). Combination of dexmedetomidine (0.1 mg kg–1) and midazolam (2 mg kg–1) decreased fR, PR and SpO2 regardless of the administration route in New Zealand White rabbits. A more rapid action and shorter duration of sedation were observed after treatment IN than after treatment IM administration.