There is increasing evidence that chronic sleep disorders in children with autism spectrum disorder (ASD), Angelman Syndrome (AS) and Smith-Magenis syndrome (SMS) are associated with disturbed melatonin secretion and melatonin administration has been shown to be effective in these populations. For children who have difficulties swallowing a tablet, Neurim has developed an age-appropriate Melatonin formulation in the form of mini-tablets which have the same dissolution profile as the Circadin® tablets product, thus should produce the same melatonin concentration-time profile with the same effects. This study concerns the pharmacokinetic study.

The purpose of this study is to :

* Establish the 24 hour baseline profile of endogenous saliva melatonin concentrations and urine 6-SMT excretion in children aged 2 up to and including 17 years with neurodevelopmental disorders with sleep disturbances.
* Establish the concentration-time profile of saliva melatonin concentrations and 24 hour 6-SMT urine excretion after 2 and 10 mg Circadin® mini-tablets single dose administration in children aged 2 up to and including 17 years with neurodevelopmental disorders with sleep disturbances.
* Evaluate the adverse event profile after a single dose of 2 or 10 mg Circadin® mini-tablets in children aged 2 up to and including 17 years with neurodevelopmental disorders with sleep disturbances.