A new study suggests that by testing genetic differences, measuring the effectiveness of ADHD medications might soon be
possible. ADHD refers to Attention Deficit – Hyperactivity Disorder, one of the most common neuropsychiatric disorders in
children and adolescents. According to Dr. Mark Stein, principal investigator of the study and director of the
Hyperactivity, Attention, and Learning Problems Clinic at the University of Illinois at Chicago, this is an exciting finding
since ADHD is such a common disorder and it is often difficult to know how patients will respond to ADHD medications. Their
hope is to take a lot of the guesswork out of why some people respond to these medications and others do not. The study found
that children with a variant form of a dopamine transporter gene, a variant known to be associated with ADHD, responded
poorly to one of the most common stimulant found in ADHD medications called methylphenidate. The transporter gene encodes a
protein on the nerve cell membrane that helps to clear the neurotransmitter dopamine from the nerve junction.
The researchers of this study tested 47 children with ADHD between 5 and 16 years old in order to determine which variant of
the dopamine transporter gene they carried. They focused on two specific variants called 9R and 10R. Researchers tested
these transporter genes to assess how varying doses of methylphenidate would affect ADHD symptoms and how the said gene is
linked to cases of impairment and the presence of side effects. Majority of the patients had one or two copies of the 10R
variant. Of these children, nearly 60 percent had excellent response to the highest dosage (54 milligrams). On the contrary,
of the patients with two copies of the 9R variant, none displayed any improvement.
According to Stein, it is not known exactly how the genetic variations prevent the patients from responding to stimulant
treatment. The next step, he says, will be to determine whether these patients respond to an alternative drug. He will then
begin recruiting subjects for a larger study to evaluate children with ADHD on two other medications to see if their genes
predict who will respond to either or both drugs. Stein also says that pharmacogenetics gives high hopes in finding an
effective and permanent treatment for ADHD. Since ADHD often runs in families, it seems likely that genetics may play a
large role in predicting medication response. But Stein and the others are not yet at the point where they can use these
findings in clinical practice. In time, it is hoped that researchers would be able to identify steps to finally develop a new
treatment with little or no risk of side effects.
Many different medications are available for the treatment of ADHD yet the room for improving these drugs and methods is
still so large. Stein says that when a patient does not respond to an ADHD medication,the patient may resort to alternative
therapies that are ineffective or even dangerous or can abandon the treatment entirely. The goal of current research is to
make a breakthrough and finally produce a treatment for ADHD that is safe, effective, and inexpensive for the thousands who
suffer from the said disease.
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