BackgroundDirect laryngoscopy and tracheal intubation can result in blood pressure and heart rate increase which in turn may lead to myocardial ischemia, cerebral hemorrhage, and even death in susceptible patients. Tizanidine is α2-receptor agonists that suppresses central sympathetic system.ObjectivesThis study evaluates the effects of oral Tizanidine on hemodynamic responses during operations and aims to determine the appropriate Propofol dosage to maintain anesthesia under BIS monitoring.Materials and MethodsA double-blind clinical trial has been performed on 70 candidates for elective abdominal surgery undergoing general anesthesia in Educational Hospital of Ghaem, Mashhad, Iran. 35 randomly selected patients (the case group) were given 4 mg of oral Tizanidine 90 minutes before the induction of anesthesia whereas the remaining subjects (the control group) were given placebo. Blood pressure and heart rate before and after induction of anesthesia, and after intubation and extubation, existence of postoperative shivering, and the needed Propofol dosage were measured and recorded. Data analysis was done with T-test and Chi-squared test, using SPSS software version 16.ResultsVariations of blood pressure and heart rate after anesthesia induction, intubation and extubation were less in Tizanidine group generally. Postoperative shivering was reported in 28.6% and 11.4% of patients in control and case group respectively. Average propofol needed dose for anesthesia maintenance in case group was 25% less than the needed amount in the control group.ConclusionsUsing oral Tizanidine as a premedication, yielded stability in blood pressure and heart rate during surgery and decreased required Propofol. Considering its short duration of action, Tizanidine use as a premedication is recommended for sedation and stabilization of hemodynamic responses during the operations.