Recent advances in pharmacological management of attention-deficit/hyperactivity disorder: moving beyond stimulants

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder characterized by impairing inattention and/or hyperactivity and impulsivity in children and adults. Although medications have been available to treat ADHD symptoms for decades, many are stimulant formulations. Stimulants, such as amphetamine and methylphenidate, are available in more than two dozen formulations, but all have similar adverse effects and carry a risk of misuse and dependence.

AREAS COVERED

In the United States (US), several nonstimulants are available to treat ADHD. Two, including atomoxetine and viloxazine extended-release (ER), are approved by the Food and Drug Administration for the treatment of ADHD in children and adults. Two others, clonidine ER and guanfacine ER, are only approved for children and adolescents in the US. Several other compounds are under investigation. Drugs in Phase 3 trials include centanafadine, solriamfetol, and L-threonic acid magnesium salt. Efficacy and safety data for nonstimulants is presented.

EXPERT OPINION

Although many effective formulations for the treatment of ADHD are available, more than 33% of children and 50% of adults discontinue treatment during the first year. The lack of individual drug response and tolerability are reasons many stop treatment. The development of new nonstimulants may offer hope for patients who need medication alternatives.

Viloxazine extended-release capsules for the treatment of attention-deficit/ hyperactivity disorder in adult patients

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder with symptoms that may persist in up to 90% of adults diagnosed during childhood and continue to cause significant impairment throughout the lifespan. In the United States (US), amphetamine and methylphenidate formulations have been available to treat ADHD for several decades. Only one nonstimulant, atomoxetine, was available for the treatment of ADHD in adults until recently. In April 2022, a second nonstimulant, viloxazine extended-release (VLX-ER), became available in the US for the treatment of adult ADHD. Efficacy was previously established in placebo-controlled trials in children and adolescents.

AREAS COVERED

VLX-ER is a norepinephrine reuptake inhibitor with serotonin activity. The efficacy in adults, adverse event profile, pharmacokinetics, drug-drug interactions, and metabolism of VLX-ER are reviewed.

EXPERT OPINION

Despite the availability of effective pharmacological treatments for ADHD, many patients discontinue treatment in less than 1 year. Stimulants are effective in more than 80% of patients; however, some may have difficulty tolerating them. Although there were no head-to-head studies, the effect size of VLX-ER in an adult efficacy trial was lower than has been shown for stimulants. Nevertheless, the approval of VLX-ER adds another effective ADHD treatment option for adults.

Functional Impairments Associated With ADHD in Adulthood and the Impact of Pharmacological Treatment

OBJECTIVE

Among untreated adults, functional impairments associated with ADHD are widespread and cumulative, and can include social, educational, and professional impairments, increased risk of accidents and mortality, and reduced quality of life. Here, we review the most prominent functional impairments in adults with ADHD and summarize evidence describing the potential role of medication in improving outcomes.

METHOD

Articles related to the search terms "ADHD," "adult," and functional impairments were identified through Google Scholar and PubMed and selected for inclusion based on four criteria: strength of evidence, relevance to current challenges in adult ADHD, impact on the field, and recency of the results.

RESULTS

We identified 179 papers to support the conclusions on the relationship between ADHD and functional impairments, and the impact of pharmacological therapy on functional impairments.

CONCLUSION

This narrative review provides evidence that pharmacological treatment can be effective in minimizing not only the symptoms of ADHD, but its functional consequences as well.

Adverse Effects of α-2 Adrenergic Agonists and Stimulants in Preschool-age Attention-deficit/Hyperactivity Disorder: A Developmental-Behavioral Pediatrics Research Network Study

OBJECTIVES

To characterize and compare the type and frequency of a range of common and uncommon adverse effects (AEs) associated with α-2 adrenergic agonist (A2A) and stimulant treatment of attention-deficit/hyperactivity disorder at preschool-age as well as to evaluate the impact of age on common AEs.

STUDY DESIGN

This was a retrospective electronic medical record review of children <72 months of age (n = 497) evaluated at outpatient developmental-behavioral pediatric practices at 7 US academic medical centers within the Developmental-Behavioral Pediatrics Research Network. Data on AEs were abstracted for children who had treatment initiated by a developmental-behavioral pediatrician with an A2A or stimulant medication between January 2013 and July 2017; follow-up was complete by February 2019.

RESULTS

A2A and stimulants had distinctive AE profiles. A2A compared with stimulants had a greater proportion with daytime sleepiness and headaches; stimulants had significantly greater proportions for most other AE, including moodiness/irritability, difficulty with sleep, appetite suppression, stomachaches, skin picking/repetitive behaviors, withdrawn behavior, and weight loss. Younger age was associated with disruptive behavior and difficulty with sleep.

CONCLUSIONS

Stimulants had a greater rate of most AEs compared with A2A. AE profiles, together with efficacy, should inform clinical decision-making. Prospective randomized clinical trials are needed to fully compare efficacy and AE profiles of A2A and stimulants.

Viloxazine, a Non-stimulant Norepinephrine Reuptake Inhibitor, for the Treatment of Attention Deficit Hyperactivity Disorder: A 3 Year Update

Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder in childhood. Current treatment options for ADHD include pharmacological treatment (stimulants, non-stimulants, anti-depressants, anti-psychotics), psychological treatment (behavioral therapy with or without parent training, cognitive training, neurofeedback), and complementary and alternative therapies (vitamin supplementation, exercise). Central nervous system (CNS) stimulants are the primary pharmacological therapy used in treatment; however, these stimulant drugs carry a high potential for abuse and severe psychological/physical dependence. Viloxazine, a non-stimulant medication without evidence of drug dependence, is a selective norepinephrine reuptake inhibitor that has historically been prescribed as an anti-depressant medication. The extended-release (ER) form was approved by the US Food and Drug Administration (FDA) in April 2021 for the treatment of ADHD in pediatric patients aged 6-17 years. Phase 2 and 3 randomized control trials have demonstrated significant efficacy of viloxazine in improving ADHD symptoms versus placebo. Related to its long-standing use as an antidepressant, the safety profile and pharmacokinetics of viloxazine are well understood. Viloxazine appears to be a suitable alternative to current standard-of-care pharmacotherapy for ADHD, but the further investigation remains to be done in comparing its efficacy to that of current treatments.

Evaluating the pharmacokinetics of extended release viloxazine in the treatment of children with attention-deficit/hyperactivity disorder

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder of childhood and impacts function negatively in multiple settings. Current treatments include stimulants, which inhibit the reuptake of dopamine and norepinephrine, a nonstimulant norepinephrine reuptake inhibitor (NRI) atomoxetine, and alpha-2 agonists clonidine extended release (ER) and guanfacine ER. Despite the effectiveness of these medications some patients do not respond to available drugs or may experience tolerability issues that hinder their use.

AREAS COVERED

Viloxazine, a serotonin norepinephrine modulating agent, was used outside of the United States (U.S.) as an effective antidepressant for several decades, but its use fell out of favor due to the need for multiple daily dosing. An ER viloxazine formulation was recently approved by the U. S. Food and Drug Administration (FDA) for the treatment of ADHD. The efficacy, pharmacokinetics and metabolism of viloxazine and viloxazine ER are reviewed.

EXPERT OPINION

Viloxazine ER is the first nonstimulant approved to treat ADHD in more than a decade. Although they have not been directly compared, the effect size of viloxazine ER is less than has been observed for stimulants. However, its pharmacokinetic properties and tolerability make viloxazine ER a useful addition to the collection of FDA approved ADHD treatments.

Evaluating Guanfacine Hydrochloride in the Treatment of Attention Deficit Hyperactivity Disorder (ADHD) in Adult Patients: Design, Development and Place in Therapy

Attention-deficit/hyperactivity disorder (ADHD) is characterized by age-inappropriate and impairing levels of inattention, hyperactivity, or impulsivity, or a combination of these characteristics. It is estimated to affect around 4% of adults worldwide. In the past few decades, prescriptions for ADHD drugs (psychostimulants and non-psychostimulants) have increased significantly. However, the efficacy and safety of adult ADHD medications remains controversial. Guanfacine extended-release (GXR) is a non-psychostimulant ADHD drug that is a selective α2A-adrenergic receptor agonist, first approved for treatment of adult ADHD in Japan in June 2019. Our aim was to provide an overview of GXR pharmacology and review the studies on efficacy and safety that have been conducted in adults with ADHD. The beneficial actions of guanfacine are thought to be attributed to the strengthening of prefrontal cortical network connections, which regulate attention, emotion, and behavior via the activity at post-synaptic α2A receptors. Current evidence of GXR efficacy and safety suggests that GXR is an effective monotherapy treatment option for adults with ADHD.

Once-Daily SPN-812 200 and 400 mg in the treatment of ADHD in School-aged Children: A Phase III Randomized, Controlled Trial

PURPOSE

SPN-812 (viloxazine extended-release) is under investigation for the treatment of attention-deficit/hyperactivity disorder (ADHD) in children and adolescents. This Phase III study evaluated the efficacy and tolerability of SPN-812 200 and 400 mg once daily in children 6-11 years of age with ADHD.

METHODS

Patients were randomly assigned to receive SPN-812 200 mg, SPN-812 400 mg, or placebo, once daily for 8 weeks (including ≤3 weeks titration period). The primary efficacy endpoint was the change from baseline (CFB) in ADHD Rating Scale (RS)-5 Total score at end of study (EOS). Key secondary endpoints included Clinical Global Impression-Improvement (CGI-I) score at EOS, CFB in Conners 3-Parent Short Form (PS) composite T-score at EOS, and CFB in Weiss Functional Impairment Rating Scale-Parent (WFIRS-P) Total average score at EOS.

FINDINGS

A total of 313 patients were enrolled, with 301 in the intent-to-treat population (194 boys, 107 girls; mean age [SD], 8.4 [1.7] years). At EOS, the CFBs in ADHD-RS-5 Total score and CGI-I score were significantly improved with both 200- and 400-mg/d SPN-812 versus placebo (ADHD-RS-5, P = 0.0038 and 0.0063, respectively; CGI-I, P = 0.0028 and 0.0099). At EOS, the CFB in Conners 3-PS composite T-score was significantly improved with 200- (P = 0.0064), but not 400-mg/d (P = 0.0917), SPN-812 compared to placebo. No significant difference between the groups was found in WFIRS-P Total average score. The rate of discontinuations due to adverse events in both SPN-812 treatment groups combined was <5%.

IMPLICATIONS

SPN-812 200 and 400 mg once daily was associated with improvements in ADHD symptoms in school-aged children and was generally well tolerated. ClinicalTrials.gov identifier: NCT03247543.

Frontal Cortical Monoamine Release, Attention, and Working Memory in a Perinatal Nicotine Exposure Mouse Model Following Kappa Opioid Receptor Antagonism

Perinatal nicotine exposure (PNE) produces frontal cortical hypo-dopaminergic state and attention and working memory deficits consistent with neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD). Methylphenidate alleviates ADHD symptoms by increasing extracellular dopamine and noradrenaline. Kappa opioid receptor (KOR) antagonism may be another mechanism to achieve the same results because KOR activation inhibits frontal cortical dopamine release. We administered the selective KOR antagonist norbinaltorphimine (norBNI) (20 mg/kg; intraperitoneal) or methylphenidate (0.75 mg/kg; intraperitoneal) to PNE mouse model and examined frontal cortical monoamine release, attention, and working memory. Both compounds increased dopamine and noradrenaline release but neither influenced serotonin release. Both compounds improved object-based attention and working memory in the PNE group, with norBNI's effects evident at 2.5 h and 5.5 h but absent at 24 h. Methylphenidate's effects were evident at 0.5 h but not at 2.5 h. norBNI's effects temporally coincided with frontal cortical c-Jun N-terminal kinase phosphorylation. norBNI did not alter tissue dopamine content in the nucleus accumbens, offering preliminary support for lack of reinforcement.

A Phase II Double-Blind, Placebo-Controlled, Efficacy and Safety Study of SPN-812 (Extended-Release Viloxazine) in Children With ADHD

Objective: The objective of this study is to evaluate efficacy and safety of SPN-812 (extended-release viloxazine) for ADHD in children aged 6 to 12 years. Method: In an 8-week study, 222 participants were randomized to placebo or SPN-812 100, 200, 300, or 400 mg/day. Measurements included ADHD Rating Scale (RS)-IV total score and Clinical Global Impression-Severity (CGI-S) and Clinical Global Impression-Improvement (CGI-I) scores. Safety assessments included laboratory and electrocardiogram (ECG) measurements, suicidality monitoring (Columbia-Suicide Severity Rating Scale), and adverse event (AE) reporting. Results: Significant improvements in ADHD-RS-IV total score were observed for 200, 300, and 400 mg dose groups versus placebo (p < .05; effect size [ES] = 0.547, 0.596, and 0.623). CGI-I score for the 300 mg group and CGI-S score for all SPN-812 groups except for 100 mg improved significantly (p < .05) versus placebo. The most frequent AEs (≥15%) were somnolence, headache, and decreased appetite. Conclusion: SPN-812 significantly reduced the severity of ADHD symptoms and was well tolerated. The efficacy and safety of SPN-812 are being investigated in Phase III trials.

Duloxetine in adults with ADHD: a randomized, placebo-controlled pilot study

OBJECTIVE

To assess the effect of duloxetine on ADHD in adults.

METHOD

In a 6-week double-blind trial, 30 adults with ADHD received placebo or duloxetine 60 mg daily. The Conners' Adult ADHD Rating Scale (CAARS) and the Clinical Global Impression Scales (CGI) were used to assess symptom severity and clinical improvement. The Hamilton Anxiety Rating Scale (HARS) and the Hamilton Depression Rating Scale (HDRS) were used to measure the effect on anxiety and depressive symptoms.

RESULTS

The Duloxetine group showed lower score on CGI-Severity at Week 6 (3.00 vs. 4.07 for placebo, p < .001), greater improvement on CGI-Improvement (2.89 vs. 4.00 at Week 6, p < .001), and greater decreases on five of eight subscales of the CAARS. There was no treatment group effect on HDRS or HARS scores.

CONCLUSION

Duloxetine may be a therapeutic option for adults with ADHD, but further studies are required to replicate these findings in larger samples.

Randomized, double-blind trial of guanfacine extended release in children with attention-deficit/hyperactivity disorder: morning or evening administration

OBJECTIVE

To examine the efficacy and tolerability of guanfacine extended release (GXR) administered in the morning or evening in children with attention-deficit/hyperactivity disorder (ADHD).

METHOD

In this multicenter, double-blind, placebo-controlled, dose-optimization study, children 6 to 12 years of age with ADHD were randomized to receive GXR (1-4 mg/d) in the morning and placebo in the evening (GXR am), placebo in the morning and GXR in the evening (GXR pm), or twice-daily placebo. The primary efficacy measure was the ADHD Rating Scale-IV (ADHD-RS-IV).

RESULTS

A total of 333 child participants received study drug in the following cohorts: GXR am (n = 107), GXR pm (n = 114), or placebo (n = 112). Mean (standard deviation) changes from baseline to week 8 (visit 10 or last observation carried forward) in ADHD-RS-IV total scores were significant for both GXR treatment groups combined (GXR all-active: -20.0 [12.97]) and separately (GXR am: -19.8 [12.95]; GXR pm: -20.1 [13.04]) compared with placebo (-11.0 [12.93]; p < .001 for all). Most spontaneously-elicited treatment-emergent adverse events were mild or moderate in severity; the most common was somnolence (GXR all-active: 44.3%; GXR am: 46.7%; GXR pm: 42.1%; placebo: 12.5%).

CONCLUSIONS

GXR administered either in the morning or evening was associated with significant and clinically meaningful improvements in ADHD symptoms. The levels of response and tolerability observed with GXR were similar regardless of time of dosing (morning versus evening), indicating that once-daily GXR monotherapy is effective whether administered in the morning or evening. Clinical trial registration information-Tolerability and Efficacy of AM and PM Once Daily Dosing With Extended-release Guanfacine Hydrochloride in Children 6-12 With Attention-Deficit/Hyperactivity Disorder (ADHD) (The ADHD Tempo Study.

Sustained treatment effect in attention-deficit/hyperactivity disorder: focus on long-term placebo-controlled randomized maintenance withdrawal and open-label studies

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that often persists throughout life. Approximately two-thirds of patients with a childhood diagnosis of ADHD continue to experience clinically significant symptoms into adulthood. Nevertheless, most of these individuals consider themselves “well,” and a vast majority discontinue medication treatment during adolescence. As evidence concerning the adult presentation of ADHD becomes more widely accepted, increasing numbers of physicians and patients will face decisions about the benefits and risks of continuing ADHD treatment. The risks associated with psychostimulant pharmacotherapy, including abuse, dependence, and cardiovascular events, are well understood. Multiple clinical trials demonstrate the efficacy of psychostimulants in controlling ADHD symptoms in the short term. Recent investigations using randomized withdrawal designs now provide evidence of a clinically significant benefit with continued long-term ADHD pharmacotherapy and provide insight into the negative consequences associated with discontinuation. Because many patients lack insight regarding their ADHD symptoms and impairments, they may place a low value on maintaining treatment. Nevertheless, for patients who choose to discontinue treatment, physicians can remain a source of support and schedule follow-up appointments to reassess patient status. Medication discontinuation can be used as an opportunity to help patients recognize their most impairing symptoms, learn and implement behavioral strategies to cope with ADHD symptoms, and understand when additional supportive resources and the resumption of medication management may be necessary.

A review of the abuse potential assessment of atomoxetine: a nonstimulant medication for attention-deficit/hyperactivity disorder

RATIONALE

Treatment of attention-deficit/hyperactivity disorder (ADHD) has for many years relied on psychostimulants, particularly various formulations of amphetamines and methylphenidate. These are central nervous system stimulants and are scheduled because of their abuse potential. Atomoxetine (atomoxetine hydrochloride; Strattera®) was approved in 2002 for treatment of ADHD, and was the first nonstimulant medication approved for this disorder. It was classified as an unscheduled medication indicating a low potential for abuse. However, the abuse potential of atomoxetine has not been reviewed.

OBJECTIVES

In this article, we review the evidence regarding abuse potential of atomoxetine, a selective inhibitor of the presynaptic norepinephrine transporter, which is unscheduled/unrestricted in all countries where it is approved.

METHODS

Results from receptor binding, in vitro electrophysiology, in vivo microdialysis, preclinical behavioral, and human laboratory studies have been reviewed.

RESULTS

Atomoxetine has no appreciable affinity for, or action at, central receptors through which drugs of abuse typically act, i.e., dopamine transporters, GABA(A) receptors, and opioid μ receptors. In behavioral experiments in rodents, atomoxetine does not increase locomotor activity, and in drug discrimination studies, its profile is similar to that of drugs without abuse potential. Atomoxetine does not serve as a reinforcer in monkey self-administration studies, and human laboratory studies suggest that atomoxetine does not induce subjective effects indicative of abuse.

CONCLUSION

Neurochemical, preclinical, and early clinical studies predicted and supported a lack of abuse potential of atomoxetine, which is consistent with the clinical trial and postmarketing spontaneous event data in the past 10 years.