Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 57 5 2019 09 30 316 319 EN Pejman Pourfakhr Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Seyed Hashem Ziaei Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Farhad Etezadi Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Mohammad Reza Khajavi Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Mohamad Reza Sharifnia Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran 2019 02 27 2019 06 17 Fentanyl-induced cough (FIC) is a known complication, and many studies have been conducted to prevent it. The aim of this study was to evaluate the effectiveness of Diphenhydramine as an antihistamine in suppressing of FIC during induction of anesthesia. In a prospective, double-blind, randomized controlled trial, a total of 100 patients, ASA Class I and II, scheduled for elective laparoscopy surgery were randomly assigned into two equally sized groups (n=50). Diphenhydramine diluted with distilled water as 10 mg/ml. Then, patients in Group D, received diphenhydramine 30 mg (3 ml) through peripheral IV line within 1 min and Group C received the same volume normal saline 0.9% as placebo. Two min later, fentanyl 2 µg/kg was administered through the peripheral IV line within 5 sec in all patients. The occurrence and intensity of cough within 2 min after the fentanyl injection were observed and recorded by a resident who was blinded to the study groups. The frequency of PONV, analgesic requirement in the recovery room and as a secondary outcome were recorded. The incidences of FIC were 47% in the control group, and there is no cough in the diphenhydramine group (P=0.02). The frequency of PONV was also reduced in diphenhydramine group (16% vs. 40%) and less number of patients in diphenhydramine group was needed to analgesia in the recovery room (60% vs. 82%). Our study determines that diphenhydramine (30 mg, IV) bolus injection 2 min before fentanyl injection can prevent FIC and PONV and also reduce analgesic requirement inthe recovery room.     https://acta.tums.ac.ir/index.php/acta/article/view/7735 https://acta.tums.ac.ir/index.php/acta/article/download/7735/5260