Adult attention deficit hyperactivity disorder: a comprehensive review

Attention deficit hyperactivity disorder (ADHD) is a common childhood disorder, with only 2-3% prevalence into adulthood. The epidemiology and proposed causes of ADHD are multifactorial, including genetic, prenatal and environmental influences. The diagnosis of ADHD is often complicated by masking coping mechanisms, an overlap of symptoms with other, more commonly diagnosed disorders. Traditionally, it has been treated with stimulant medications. Non-stimulant options often target norepinephrine and dopamine regulation and are preferred in cases of comorbid substance use disorder, anxiety and other complicating factors, due to an improved side-effect profile and patient preference. They include atomoxetine and viloxazine. The latter, Viloxazine, in the form of extended-release capsules, is the first novel, non-stimulant option approved for adults with ADHD, in the past two decades. Its therapeutic effects are predominantly produced by its action as a norepinephrine reuptake inhibitor and may also modulate the serotonergic system. Viloxazine is relatively safe and effective in treating other disorders such as depression, anxiety, epilepsy and substance use disorder. Its pharmacokinetics includes metabolization by CYP enzymes. As antiepileptics inhibit CYP1A2, therefore, a special consideration would be needed, when co-administering with anti-epileptic drugs. Similarly, individuals with liver or cardiovascular disease and a personal or family history of bipolar disorder require close monitoring, while on this medication. A thorough review of the history, mechanism of action, pharmacokinetics and drug-drug interactions has been presented here, with special attention on treatment in adults with comorbid conditions. This study conducted an all-language literature search on Medline, Cochrane, Embase, and Google Scholar until December 2022. The following search strings and Medical Subject Headings (MeSH) terms were used: "Viloxazine," "ADHD," "Stimulants," and "adult ADHD." We explored the literature on the growing knowledge of Viloxazine. A thorough review of the history, mechanism of action, pharmacokinetics, and drug-drug interactions are reviewed here with special attention on treatment in adults with comorbid conditions.