Background and Objective: We evaluated the effects of dexmedetomidine pretreatment on bupivacaine cardiotoxicity in anesthetized rats.,Methods: Sixteen Wistar-Albino male rats (300-400 g) were anesthetized with ketamine. Electrocardiographic and invasive blood pressure monitoring were performed, and the results were continuously recorded. The rats were randomized into 2 groups. In group D, rats were pretreated with intravenous dexmedetomidine at a dose of 10 mu g/kg (n = 8), whereas in group S, rats were pretreated with intravenous saline (n = 8). Fifteen minutes later, bupivacaine was infused at a rate of 3 mg/kg per minute until cardiac asystole Occurred. The timing of specific cardiotoxic events (a 25%, 50%, and 75% reductions of mean arterial pressure and heart rate as well as occurrence of the first arrhythmia and asystole) was recorded.,Results: Dexmedetomidine pretreatment reduced the heart rates and mean arterial pressures of the rats who received it (P < 0.05). Dexmedetomidine pretreatment before bupivacaine administration also significantly increased the time to the 25%, 50%, and 75% reductions in mean arterial pressure and the time to the 25% and 50% reductions in heart rate (P < 0.05). In addition, dexmedetomidine significantly increased the time to first arrhythmia and time to asystole (P < 0.05) in the rats who received it before receiving bupivacaine.,Conclusions: Dexmedetomidine pretreatment delays the effects of bupivacaine cardiotoxicity.