Electrocardiographic assessment of antianxiety medication in dogs and correlation with serum drug concentration

Objectives-To determine effects of tricyclic antidepressants (TCA) on the E CG of dogs treated for behavioral conditions and to examine correlations be tween ECG findings and serum concentrations of these medications. Design-Repeated-measures study. Animals-39 client-owned dogs with behavioral problems. Procedure-Two groups of dogs with behavioral problems were evaluated. In gr oup 1 (n = 20), ECG tracings were recorded before starting treatment with T CA and again after treatment for greater than or equal to 1 month. Dogs in group 2 were already on long-term maintenance amounts of antianxiety medica tion when ECG tracings were recorded and serum concentrations of medication s were obtained. Results-Significant differences were not detected for dogs in group 1 betwe en ECG values measured before and after TCA administration. The ECG values for dogs in group 2 did not differ significantly from the mean of group-1 d ogs before receiving medication or from the reference range used at our fac ility. Duration of the P wave had a significant positive correlation with s erum concentrations of clomipramine but significant negative correlation wi th serum concentrations of amitriptyline. The QT interval corrected for hea rt rate had a significant negative correlation with serum concentrations of amitriptyline. Conclusions and Clinical Relevance-Amitriptyline and clomipramine administe red at standard dosages apparently do not cause ECG abnormalities in health y dogs with behavioral problems. These medications should be used cautiousl y in dogs with conduction abnormalities, and clinicians should periodically monitor ECG and use good clinical judgment to weigh risks and benefits of medications for the safety of each dog.