Effects of clomipramine hydrochloride on heart rate and rhythm in healthy dogs

Objective-To determine the effects of clomipramine hydrochloride on heart r ate and rhythm in dogs. Animals--17 healthy Beagles. Procedures--in experiment 1, 8 dogs received placebo or clomipramine (20 mg /kg of body weight, q 24 h, PO) for 7 days in a 2-way crossover design. In experiment 2, 9 dogs were evaluated for 48 hours before and 24 hours after oral administration of clomipramine (4 or 12 mg/kg) in a 2-way crossover de sign. Electrocardiogram and heart rate were monitored continuously by use o f telemetry. Results--A significant diurnal rhythm in heart rate was detected; minimum v alues were recorded at night. Administration of 20 mg of clomipramine/kg in duced a significant reduction in heart rate, with peak effect achieved appr oximately 12 hours after dosing. Administration of 4 or 12 mg of clomiprami ne/kg did not result in significant changes in heart rate. Sinoatrial and s econd-degree atrioventricular block and ventricular escape beats were obser ved during periods of slow heart rate in more dogs that received clomiprami ne (3 to 4 of 8 dogs), compared with dogs that received placebo (1 to 2 of 8 dogs), but this difference was not significant. Conclusions and Clinical Relevance--Short-term administration of clomiprami ne induced benign cardiovascular effects in dogs rather than the potentiall y dangerous arrhythmias or tachycardia reported following administration of tricyclic antidepressants to humans, Precautions regarding cardiovascular effects may not be needed for the use of clomipramine in healthy dogs.