Comparison of the sedative effects of medetomidine administered intranasally, by atomization or drops, and intramuscular injection in dogs.

OBJECTIVE: To compare the sedative effects of intranasal atomization (INA) of medetomidine with intranasal drops (IND) and intramuscular (IM) injection in healthy dogs. STUDY DESIGN: Prospective, blinded, randomized study. ANIMALS: A group of 18 mixed-breed shelter-owned dogs weighing 27 ± 4.3 kg (mean ± standard deviation). METHODS: The dogs were randomly assigned to equal groups of six dogs for administration of medetomidine (40 µg kg-1) by INA, IND and IM routes. Ease of administration was evaluated using a resistance scale. Composite sedation score (CSS), heart rate (HR) and respiratory frequency (fR) were measured immediately before (T0, baseline) and after drug administration at time points 15, 45, 75 and 120 minutes. The time of onset of sedation was recorded. Ease of administration and onset of sedation were analysed by the Kruskal-Wallis and post hoc Dunn's tests. Repeated measures analysis of anova and least significant difference tests were used to analyse CSS, HR and fR over time. Tukey's post hoc test was used for time point comparisons among groups. Significance was set at p < 0.05. RESULTS: No differences were detected among groups for ease of administration (p = 0.346). CSS increased in all groups from baseline values. Onset of sedation in IM was 6.3 ± 2.0 minutes, in INA was 7.2 ± 2.5 minutes and in IND was 20.7 ± 5.4 minutes. CSS in IND was lower than in the other groups at T15 and lower than in INA at T45. CSS was not different between IM and INA. HR and fR decreased in all groups compared with respective baseline values. HR in IND was lower than in IM at T45-T120. CONCLUSIONS AND CLINICAL RELEVANCE: INA medetomidine (40 µg kg-1) can be an alternative and noninvasive route to IM injections for sedating healthy dogs. IND resulted in a slow onset of sedation.