The effect of preanaesthetic oral trazodone hydrochloride on the induction dose of propofol: a preliminary retrospective study.

Objective: To determine whether the administration of trazodone to dogs 2 hours prior to radiotherapy treatment reduced the dose of propofol required to induce anaesthesia.

Study Design: Retrospective, crossover, case-matched study.

Animals: Records of 30 client-owned dogs.

Methods: Anaesthetic records from all dogs undergoing weekly radiotherapy treatment between January 2020 and December 2020 were retrospectively assessed. All dogs were premedicated with 10 μg kg alfentanil and 12 μg kg atropine intravenously (IV) and anaesthesia was induced with IV propofol. In part 1, the propofol induction dose was compared between anaesthetics when trazodone was administered prior to the anaesthetic (T) versus not (NT). For part 2, control dogs not administered trazodone during the treatment course were case-matched based on bodyweight and tumour location and type. The propofol induction dose was compared between the first (C1) and last (C2) anaesthetic to identify the effects of confounding factors. A Wilcoxon signed-rank test for repeated measurements was performed to identify any significant differences in the propofol induction dose between NT and T in the study dogs and between C1 and C2 in the control dogs.

Results: In part 1, 15 study dogs that were administered trazodone prior to at least one anaesthetic were identified. A significant difference in propofol induction dose between groups NT and T was identified [3.3 (2.1-7.4) and 2.0 (1.5-5.0) mg kg, respectively; p = 0.003]. In part 2, 15 dogs were case-matched to the study cohort. The dose of propofol administered did not differ between the first and last anaesthetic [2.5 (1.6-6.4) and 2.6 (1.9-8.9) mg kg, respectively; p = 0.638].

Conclusions And Clinical Relevance: Preanaesthetic trazodone administration reduced the induction dose of propofol compared to when it was not administered to dogs following premedication with IV atropine and alfentanil.