Targeting the Neurobiology of RRB in Autism Using N-acetylcysteine: Single-dose

Inclusion Criteria:

   - children between 3 years and 12 years 11 months at the time of consent

   - diagnosis of Autism Spectrum Disorder confirmed with the Autism Diagnostic
   Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule-2 (ADOS-2),
   or Brief Observation of Symptoms of Autism (BOSA), or Childhood Autism Rating Scale-
   Second Edition (CARS-2).

   - at least moderate Restricted and Repetitive Behaviors severity defined by a Children's
   Yale-Brown Obsessive Compulsive Scale for children with autism spectrum disorder score
   ≥ 11,

   - physical development indicative of prepubescence as defined by the criteria for Tanner
   Stage 1,

   - medically stable,

   - passes MR safety screening (e.g., no metal in the body).

Exclusion Criteria:

   - presence of known genetic abnormalities associated with Autism Spectrum Disorder (e.g.
   Fragile X),

   - current or life-time diagnosis of severe psychiatric disorder (e.g., schizophrenia),

   - presence of significant medical problems that would interfere with participation,

   - the inability of at least one caregiver to speak/read English to a sufficient level to
   complete study requirements and materials,

   - individuals taking antioxidant agents and glutathione prodrugs, or

   - the inability/unwillingness to swallow an agent during the screening visit.