Randomized Controlled Study of Donepezil in Fragile X Syndrome

Inclusion Criteria:

   1. confirmed genetic diagnosis of fragile X syndrome

   2. age >=12, <=29

   3. Verbal IQ >= 50, <=75

   4. Tanner pubertal stage >= 3

Exclusion Criteria:

   1. Current or lifetime DSM-IV diagnosis of bipolar disorder, schizophrenia,
   schizoaffective disorder, or psychotic disorder, NOS based upon reported history

   2. Poorly controlled seizure disorder or taking more than one anticonvulsant (subjects
   cannot be prescribed carbamazepine, phenytoin, or phenobarbital due to potential
   interaction effects with donepezil). The investigators will permit one anticonvulsant
   as monotherapy for seizures if the seizure disorder is well controlled with no
   evidence of break through seizures within the past year

   3. Concomitant or anticipated use of other medications having prominent effects on the
   cholinergic system (e.g., bethanechol, benztropine, atropine, succinylcholine)

   4. Medications or nutritional supplements that have the potential to significantly alter
   donepezil levels, clinical effects or adverse reactions (antifungal agents,
   corticosteroids, erythromycin, beta-blockers, calcium channel blockers, NSAIDs, gingko
   biloba, St. John's wort)

   5. Medical illnesses where donepezil could worsen the condition such as asthma, cardiac
   conduction abnormalities, urinary obstruction or gastrointestinal disease with gastric
   bleeding

   6. Pregnancy or sexually active females not using a reliable method of contraception

   7. If considering participation in brain MRI part of the study, then any
   contraindications for MRI (e.g., orthodontia, metal in or on the body, etc.)