A clinical trial to study the effect of drug on IQ and behavioral problem in Children with Fragile X Syndrome

INTERVENTION: Intervention1: Donepezil: 2.5mg od for the first 4 weeks than 5 mg od for the next 8 weeks Control Intervention1: Placebo: 2.5mg od for the first 4 weeks than 5 mg od for the next 8 weeks CONDITION: Fragile X syndrome PRIMARY OUTCOME: Intelligence Quotient by Kulshreshta adaptation of the Stanford ‐ Binet Test‐‐‐‐‐‐Timepoint: Baseline & 12 week SECONDARY OUTCOME: Childhood Autism Rating Scale‐‐‐‐‐‐Timepoint: Baseline, 12 Week INCLUSION CRITERIA: 1.Confirmed genetic diagnosis of fragile X syndrome by PCR & Southern blot; 2. Age 6‐15 yrs; 3.Regardless of their IQ level if they were able to complete the required neuropsychological testing