Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 10 Supp. 2 2024 10 06 535 540 Azim Honarmand Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Mohammadreza Safavi Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Nasim Cheshmaviz School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran 2024 04 24 2024 05 15 Background: Reflex cough is a common complication after fentanyl injection during anesthesia. Several studies have tried different medications to control fentanyl-induced cough (FIC). Aim: Our study evaluated the effect of different ketamine dosage on preventing fentanyl induced cough. Methods: We randomly assigned 80 participants into four groups. Group 1 was administered 0.15 mg/kg, Group 2 received 0.2 mg/kg, Group 3 was given 0.25 mg/kg of intravenous ketamine one minute prior to fentanyl injections, while Group 4 received an equivalent volume of 0.9% normal saline. Results: The incidence and severity of cough was evaluated by FIC score. The incident of cough was significantly lower in Groups 3, 2 and 1 in comparison to Group 4 (0, 5, 30 respectively vs 85, p<0.001). The cough severity was significantly lower in Groups 3, 2 and 1 in comparison to Group 4 (p<0.001). Conclusion: Intravenous ketamine 0.25 mg/kg, significantly decreased the severity and frequency of cough compared with 0.20 and 0.15 mg/kg IV ketamine. https://aacc.tums.ac.ir/index.php/aacc/article/view/994