Clinical Assistant Professor North Carolina State University Raleigh, NC, United States
Abstract: Background- Trazodone is a serotonin receptor antagonist and reuptake inhibitor increasingly used in dogs for anxiolysis.Hypothesis/Objectives- To determine the effect of trazodone on heart rate (HR), heart rate variability (HRV), and QT intervals (QTi) in dogs after oral administration of trazodone or placebo.Animals- Twenty healthy adult client-owned dogs.Methods- Dogs were randomized in a double-blinded, placebo-controlled crossover trial. Dogs received trazodone (6 mg/kg q8h) or placebo for 24-hrs during which a 24-hr ambulatory ECG (Holter) was recorded. Diagnostic ECGs and behavior scores were obtained before and after the 24-hr study period. Following a minimum 1-week washout period, dogs received the alternate study drug, and all procedures were repeated. Owners scored the dog’s behavior change at home during each of the 24-hr study periods. Linear and mixed models were used for statistical analyses.Results- Dogs receiving trazodone had higher average HRs (P = 0.035), higher minimum HRs (P < 0.001). Conclusions and Clinical Importance- Trazodone increased HR and decreased HRV. Explanations include a previously described anticholinergic effect or a possible decrease in blood pressure causing a HR response. Blood pressure measurement was not performed as part of this study. The lack of demonstrable effect on QTi is reassuring in this cohort of healthy dogs using standard trazodone dosing.
