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 Kg/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 G 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 G 0.05). In addition, dexmedetomidine significantly increased the time to first arrhythmia and time to asystole (P G 0.05) in the rats who received it before receiving bupivacaine. CONCLUSIONS Dexmedetomidine pretreatment delays the effects of bupivacaine cardiotoxicity.