en تخصصي Special مقالات اصيل Original Article <span style="font-family:Times New Roman;"><span style="font-size:11pt"><span style="line-height:150%"><span calibri=""><b><span garamond="">Background</span></b><span garamond="">: We aimed to investigate the effect of preoperative administration of oral tizanidine on postoperative pain intensity after bimaxillary orthognathic surgery.</span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><span calibri=""><b><span garamond="">Methods</span></b><span garamond="">: <span style="color:black">All healthy skeletal class III patients who were candidates </span>for bimaxillary orthognathic surgery were enrolled in this triple-blind randomized clinical trial. The study was carried out in the Maxillofacial Surgery Department of Qaem Hospital, Mashhad, Iran; from January 2021 to November 2021.</span> <span garamond="">The consecutive patients were randomly divided into tizanidine and placebo groups. One hour prior to anesthesia induction, the tizanidine group received 4 mg Tizanidine dissolved in 10 ml apple juice, whereas the placebo group received an identical glass of plain apple juice. All operations were performed by the same surgical team, under the same general anesthesia protocol. Postoperative pain was measured using the Visual Analogue Scale (VAS) at 3, 6, 12, 18, and 24 hours. For statistical analysis; the significance level was set at 0.05 using SPSS 23.</span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><span calibri=""><b><span garamond="">Results</span></b><span garamond="">: A total of 60 consecutive patients, consisting of 36 females (60%) and 24 males (40%) with an average age of 25.4 &plusmn; 6.0 were recruited. An increasing trend was noticed in the amount of perceived postoperative pain from the 3^rd till 12^th hour, and then decreased afterward. Nevertheless, the average amount of pain was significantly lower in the tizanidine compared to the placebo group, in all the evaluated time intervals (<i>P</i><0.001). Moreover, there was a significantly higher requirement for postoperative opioid analgesics in the placebo compared to the tizanidine group (<i>P</i>=0.011). </span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><span calibri=""><b><span garamond="">Conclusion</span></b><span garamond="">: The addition of oral tizanidine was effective in reducing postoperative pain following bimaxillary orthognathic surgery. Further studies are necessary for more relevancy.</span></span></span></span><br> &nbsp;</span> Tizanidine, Postoperative pain, Bimaxillary Orthognathic surgery 37 45 http://wjps.ir/browse.php?a_code=A-10-466-35&slc_lang=en&sid=1 Saleh Dadmehr 100319475328460012873 100319475328460012873 No Department of Oral and Maxillofacial Surgery, Student Research Committee, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Zahra Shooshtari 100319475328460012874 100319475328460012874 No Student Research Committee, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Mohammad Alipour 100319475328460012875 100319475328460012875 No Department of Anesthesiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Majid Eshghpour 100319475328460012876 100319475328460012876 No Department of Oral and Maxillofacial Surgery, Mashhad University of Medical Sciences, Mashhad, Iran. Baratollah Shaban 100319475328460012877 100319475328460012877 No Oral and Maxillofacial Diseases Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. Touraj Vaezi 100319475328460012878 100319475328460012878 No Department of Oral and Maxillofacial Surgery, Mashhad University of Medical Sciences, Mashhad, Iran. Sahand Samieirad 100319475328460012879 100319475328460012879 Yes Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.