Researchers have discovered that N-acetylcysteine (NAC), a drug that has been approved by the FDA for treatment of acetaminophen (Tylenol) overdoses, may reduce irritability in children with autism spectrum disorders (ASD).
Experts say that NAC helps maintain and restore glutathione, which plays a key role in the antioxidant defense system. Additionally, cystine as supplied by NAC treatment stimulates a protein, the cystine-glutamate antiporter, resulting in the decrease of glutamatergic neurotransmission.
NAC has two resulting effects: it may protect brain cells by raising the level of a protective antioxidant metabolite called glutathione, and it may reduce the excitability of the glutamate system by stimulating inhibitory receptors.
These drug actions are important because, although the causes of autism are unknown, it is clear that there are many influencing factors and scientists are pursuing multiple hypotheses.
Two in particular relate to NAC: one theory is that autism may be caused by an imbalance between oxidants and antioxidants in the body; the other is that the glutamate system may be dysfunctional in individuals with autism.
Autism spectrum disorders are characterized by social interaction difficulties, communication challenges and a tendency to engage in repetitive behaviors.
A common symptom of autism is irritability, a behavior that can complicate adjustment at home and other settings, and can manifest itself in aggression, tantrums, and self-injurious behavior.
In the new study, researchers at Stanford University and the Cleveland Clinic conducted a pilot trial of NAC in children with autistic disorder. Children were randomized to receive either NAC or placebo daily for 12 weeks and their symptoms were evaluated four times during that period.
They found that irritability was significantly decreased in the children who received NAC. In addition, NAC was well-tolerated and caused minimal side effects.
Lead author Dr. Antonio Hardan commented, “Data from this preliminary trial suggest that NAC has the potential to be helpful in targeting irritability in children with autism. It is also unclear if NAC improves other symptom domains in autism.”
“At this point it is too early to tell how NAC reduced irritability in autism, but this finding will be an important addition to the field if it can be replicated,” said Dr. John Krystal, Editor of Biological Psychiatry, where the study is being published.
Researchers agree that large randomized controlled trials are needed to attempt to replicate the findings from this pilot trial and to determine whether or not NAC is effective in targeting other symptoms observed in autism such as repetitive and restricted interests.