Trazodone administration does not affect platelet concentration or function in horses

OBJECTIVE: To determine the effect of a clinically relevant dose of trazodone on platelet count and function in healthy horses. STUDY DESIGN: Prospective, controlled, cross-over study. ANIMALS: Ten healthy horses. METHODS: Horses were administered either 7 mg/kg trazodone orally in corn syrup or an equal amount of corn syrup (control), every 12 h for 2 weeks. After 2 weeks, horses underwent at least a 2-week washout period before being administered the alternate treatment (trazodone or control). Blood was collected before the first treatment administration (day 0) and after 2 weeks of treatment for each phase of the study. Complete blood cell counts, platelet function assays, and plasma trazodone concentrations were assessed. Data were analyzed using repeated measures ANOVA with significance set at p < .05. RESULTS: No differences in platelet count or tests of platelet function were observed at any time point after trazodone or control treatment. There were no adverse effects of trazodone administration appreciated on repeat physical examinations or daily ataxia scoring. CONCLUSIONS: No inhibitory effects of trazodone on platelet function in horses were detected. CLINICAL SIGNIFICANCE: This study suggests administration of oral trazodone at 7 mg/kg prior to surgery is unlikely to impair platelet function in healthy horses.