In this randomized controlled trial children will be assigned to one of the three following groups (no intervention, placebo and active drug). The investigators will collect salivary samples to measure the levels of sCortisol and investigate their variation between three timepoint ( at arrival at the hospital, right before the procedure and right after the procedure). sCortisol levels will be correlated to a questionnaire evaluating the anxiety level in the patient. The research team will also evaluate the pain experienced during the procedure using the Nurse-Assessed Patient Comfort Score (NAPCOMS): a validated tool for the evaluation of pain in subjects undergoing endoscopies).