Study of Droxidopa Treatment in Adults With Attention Deficit Hyperactivity Disorder With Co-administration of Carbidopa

Attention Deficit Hyperactivity Disorder (ADHD) is a neurobiological disorder characterized
by lifelong issues of inattention, distraction, organizational difficulties, forgetfulness,
restlessness, talking out of turn, difficulty waiting and interrupting others. ADHD is the
second most common neuropsychiatric disorder affecting 4.4% of the US adult population, or
between 8-9 million individuals (Kessler et al., 2006).

Droxidopa (L-dihydroxyphenylserine (L-DOPS)) is a synthetic catecholamine which is converted
to norepinephrine (NE) via decarboxylation, resulting in increased levels of NE centrally in
the CNS and peripherally. Co-treatment with carboxylase inhibitors, such as carbidoba, given
with droxidopa, can increase the CNS levels of NE with greater crossing of the blood-brain
barrier. Droxidopa has received orphan drug approval by the FDA for the treatment of
symptomatic neurogenic orthostatic hypotension in individuals with primary autonomic
failure. The half-life of droxidopa is approximately 2-3 hours, resulting in administration
thee times daily.

As adult ADHD is characterized as a disorder of decreased NE activity in the pre-frontal
cortex, it is hypothesized that treating patients with droxidopa (in co-administration of
carbidopa) will have a positive effect on adult ADHD.