E13 - The Effect of Oral Trazodone on Ambulation and Recumbency in Horses

Abstract: Background: Trazodone may be a useful adjunct therapy in the initial management of acute laminitis cases if it minimizes ambulatory activity and/or encourages recumbency.

Hypothesis/Objectives: To evaluate the effects of oral trazodone on ambulatory activity and recumbency in healthy horses.

Animals/Methods: In a randomized cross-over design, 8 healthy research horses housed in stalls received placebo (molasses water) or trazodone at 2 dose rates (2.5 mg/kg and 7.5 mg/kg) orally every 12 h for 48 h with a 14 day washout between study periods. Forelimb step frequency was measured using a hoof mounted accelerometer and continuous video monitoring was used to detect recumbency. Groups were compared using Friedman’s test with post hoc Dunn’s test.

Results: Step frequency was significantly lower (p = 0.008) with 7.5mg/kg trazodone treatment (median 64 [IQR, 38-96] steps/h) compared to placebo (128 [78-173] steps/h), with a mean step reduction of 44 ± 11%. There was no difference in step frequency with 2.5mg/kg trazodone (110 [62-177] steps/h) compared to control (p > 0.99) or 7.5mg/kg trazodone (p = 0.07). There was no difference in the number of recumbent episodes or total duration of recumbency between any of the treatments (p = 0.92).

Conclusions/Clinical importance: Although it did not affect recumbency, trazodone at 7.5 mg/kg q12 h reduced step frequency by approximately 40%, an effect that may be clinically useful to minimize the mechanical strains associated with ambulation during acute laminitis.