Magnetic Resonance Imaging (MRI) in children requires complete immobility in a noisy and confined environment, which is often not achievable without sedation. Intranasal dexmedetomidine is an effective, non-invasive sedative agent that provides deep sedation while preserving spontaneous respiration, yet higher doses may prolong recovery or cause haemodynamic effects. However, intravenous rescue sedation may be required in some children. Oral melatonin, a natural hormone regulating circadian rhythm, has also been used safely in paediatric practice as a premedication and in combination with other sedatives, where it has caused anxiolysis, smoother recovery, and reduced emergence agitation. Previous attempts to combine dexmedetomidine with agents like midazolam, ketamine or propofol have been constrained by adverse effects, but combining it with melatonin offers a more promising and complementary approach. However, the role of melatonin as a premedication with intranasal dexmedetomidine in paediatric MRI has been evaluated sparingly. Whether melatonin enhances sedation success, reduces the requirement of rescue intravenous sedation, shortens onset time, and improves recovery when combined with intranasal dexmedetomidine remains unknown. This knowledge gap forms the basis of the present study. We hypothesize that oral melatonin given as a premedication to intranasal dexmedetomidine will increase the rate of successful MRI sedation (completion without IV rescue and with UMSS of more than or equal to 3), shorten the onset time to adequate sedation, and improve recovery characteristics, compared with intranasal dexmedetomidine alone.