New Formulations of Stimulants: An Update for Clinicians

A critical review of the dextroamphetamine transdermal system for the treatment of ADHD in adults and pediatric patients

INTRODUCTION

The dextroamphetamine transdermal system (d-ATS) is a stimulant patch recently approved by the United States (U.S.) Food and Drug Administration for the treatment of attention-deficit/hyperactivity disorder (ADHD).

AREAS COVERED

The composition of the d-ATS, pharmacokinetics, and metabolism are presented along with data from dermal trials evaluating the tolerability of patch application at various skin sites. Efficacy and safety data from a laboratory classroom study in children and adolescents including effect sizes are assessed. Pharmacokinetic-pharmacodynamic modeling of variable wear times is also discussed.

EXPERT OPINION

Although stimulants are recommended as first-line treatment for ADHD in the U.S. some patients may have difficulty swallowing intact tablets and capsules, or dislike the taste or texture of chewable, oral disintegrating, or liquid formulations. The d-ATS fills an unmet need for those with ADHD who are unable or prefer not to take medication orally. Varying wear time of the d-ATS also gives flexibility in length of stimulant effect which may be useful for patients with changing schedules. However, dermal discomfort must be considered in addition to the usual amphetamine side effects when prescribing the d-ATS. Patient and provider experience will determine how frequent the use of d-ATS becomes.

A review of amphetamine extended release once-daily options for the management of attention-deficit hyperactivity disorder

INTRODUCTION

Amphetamine preparations are one of the two categories of stimulant medications approved for the treatment of attention deficit hyperactivity disorder (ADHD). Optimal treatment of ADHD aims to reduce core symptoms for as much of the waking hours as possible, leading to longer-acting delivery formats. In addition, the pediatric population commonly has difficulty swallowing pills and manufacturers have developed a variety of options to facilitate this concern. These include chewable tablets, capsules that may be sprinkled on soft food, liquids and transdermal patches.

AREAS COVERED

This article reviews the once-daily extended-release preparations currently available for amphetamine compounds, their pharmacodynamics, and common adverse effects.

EXPERT OPINION

There is an extensive evidence base supporting use of amphetamine preparations in the treatment of ADHD. Rapid onset of action and a favorable side effect profile make these widely used. The availability of once-daily extended-release chewable tablets, capsules that can be opened and sprinkled, and liquid formulations provides clinicians with multiple options to meet the specific needs of patients with difficulty swallowing whole pills.

Switch to Lisdexamfetamine in the Treatment of Attention-Deficit Disorder at a Psychiatric Outpatient Clinic for School-Aged Children: A Danish Cohort Study

Objectives: This study aimed to examine switch from first-line methylphenidate (MPH) to lisdexamfetamine (LDX) in school-aged children with attention-deficit/hyperactivity disorder (ADHD). Methods: This is a retrospective observational study based on systematic review of patient records of all children (7-13 years) diagnosed with ADHD and referred to a Danish specialized outpatient clinic. The study included 394 children switching from MPH to LDX as either second-line or third-line treatment (atomoxetine [ATX] as second-line treatment) during the study period from April 1, 2013, to November 5, 2019. Results: One in five children switched from MPH to LDX at some point during the study period. The most frequent reasons for switching to LDX were adverse effects (AEs; 70.0% for MPH, 68.3% for ATX) and lack of efficiency (52.0% for MPH, 72.7% for ATX). Top five AEs of LDX were decreased appetite (62.4%), insomnia (28.7%), irritability/aggression (26.1%), weight decrease (21.1%), and mood swings (13.9%). MPH and LDX had similar AE profiles, yet most AEs were less frequent after switching to LDX. At the end of the study period, the majority were prescribed LDX as second-line rather than third-line treatment (86.1% in 2019). However, the likelihood of LDX as second-line treatment decreased with the number of psychiatric comorbidities, ADHD symptom severity as assessed by parents, and if AEs were a reason for MPH discontinuation. Among children observed for at least 1 year after initiation of LDX, 41.3% continued LDX treatment for a year or longer. LDX continuation was less likely if AEs were a reason for MPH discontinuation. Similarly to MPH and ATX, the most frequent reasons for LDX discontinuation were AEs (74.4%) and lack of efficiency (34.7%). Implications: The findings support LDX as an important option in the personalized treatment of children with ADHD and may support prescribers in the clinical decision-making on switching medication.

Pharmacokinetics of Long-Acting Methylphenidate: Formulation Differences, Bioequivalence, Interchangeability

BACKGROUND AND OBJECTIVE: Attention deficit hyperactivity disorder is one of the most common neuropsychiatric conditions in children, and methylphenidate (MPH) is one of the first-line therapies. MPH is available in a variety of extended-release (ER) formulations worldwide, and most formulations are not considered bioequivalent due to differences in pharmacokinetics. It is hypothesized that the current bioequivalence guidelines from the different regulatory bodies may generate inconsistent findings or recommendations when assessing the bioequivalence of ER MPH formulations. This manuscript aims to conduct a comprehensive and narrative critical literature review to analyze pharmacokinetic data pertaining to ER formulations of MPH in order to assess bioequivalence, differences in regulatory guidelines, and additional pharmacokinetic-pharmacodynamic parameters that may help define interchangeability.

METHODS

A literature search was conducted in EMBASE, Medline, and Cochrane Library with no time limits. Study characteristics, non-compartmental pharmacokinetic parameters, and bioequivalence data were extracted for analysis.

RESULTS

Thirty-three studies were identified with primary pharmacokinetic data after the administration of ER MPH, of which 10 were direct comparative studies (i.e., at least 2 formulations tested within a single setting) and 23 were indirect comparisons (i.e., different experimental settings). Two formulations were consistently reported as bioequivalent across the regulatory bodies using criteria from their guidance documents, although inconsistencies have been observed. However, when additional kinetic criteria (discussed in this manuscript) were imposed, only one study met the more stringent definition of bioequivalence. Various clinical factors also had inconsistent effects on the pharmacokinetics and interchangeability of the different formulations, which were associated with a lack of standardization for assessing covariates across the regulatory agencies.

CONCLUSION

Additional pharmacokinetic parameters and consistency in guidelines across the regulatory bodies may improve bioequivalence assessments. Based on our findings, more research is also required to understand whether bioequivalence is an appropriate measure for determining MPH interchangeability. This critical review is suitable for formulation scientists, clinical pharmacologists, and clinicians.

MicroRNAs as potential biomarkers for diagnosis of attention deficit hyperactivity disorder

Inappropriate levels of hyperactivity, impulsivity, and inattention characterize attention deficit hyperactivity disorder, a common childhood-onset neuropsychiatric disorder. The cognitive function and learning ability of children with attention deficit hyperactivity disorder are affected, and these symptoms may persist to adulthood if they are not treated. The diagnosis of attention deficit hyperactivity disorder is only based on symptoms and objective tests for attention deficit hyperactivity disorder are missing. Treatments for attention deficit hyperactivity disorder in children include medications, behavior therapy, counseling, and education services which can relieve many of the symptoms of attention deficit hyperactivity disorder but cannot cure it. There is a need for a molecular biomarker to distinguish attention deficit hyperactivity disorder from healthy subjects and other neurological conditions, which would allow for an earlier and more accurate diagnosis and appropriate treatment to be initiated. Abnormal expression of microRNAs is connected to brain development and disease and could provide novel biomarkers for the diagnosis and prognosis of attention deficit hyperactivity disorder. The recent studies reviewed had performed microRNA profiling in whole blood, white blood cells, blood plasma, and blood serum of children with attention deficit hyperactivity disorder. A large number of microRNAs were dysregulated when compared to healthy controls and with some overlap between individual studies. From the studies that had included a validation set of patients and controls, potential candidate biomarkers for attention deficit hyperactivity disorder in children could be miR-140-3p, let-7g-5p, -30e-5p, -223-3p, -142-5p, -486-5p, -151a-3p, -151a-5p, and -126-5p in total white blood cells, and miR-4516, -6090, -4763-3p, -4281, -4466, -101-3p, -130a-3p, -138-5p, -195-5p, and -106b-5p in blood serum. Further studies are warranted with children and adults with attention deficit hyperactivity disorder, and consideration should be given to utilizing rat models of attention deficit hyperactivity disorder. Animal studies could be used to confirm microRNA findings in human patients and to test the effects of targeting specific microRNAs on disease progression and behavior.

Pediatric ADHD Medication Errors Reported to United States Poison Centers, 2000 to 2021

OBJECTIVES

To investigate the characteristics and trends of out-of-hospital attention-deficit/hyperactivity disorder (ADHD) medication-related therapeutic errors among youth <20 years old reported to US poison centers.

METHODS

National Poison Data System data from 2000 through 2021 were analyzed. Population-based rates were calculated using US census data.

RESULTS

There were 124 383 ADHD medication-related therapeutic errors reported to US poison centers from 2000 through 2021, with the annual frequency increasing by 299.0% during that period. Two-thirds (66.6%) of the 87 691 first-ranked exposures involved children 6 to 12 years old, three-fourths (76.4%) were among males, and half (50.5%) involved amphetamines and related compounds. Most (79.7%) therapeutic errors were single-substance exposures. Although most (82.7%) individuals did not receive treatment in a health care facility (HCF), 2.3% were admitted to a HCF and 4.2% had a serious medical outcome. Children <6 years old were more likely to experience a serious medical outcome (odds ratio = 2.1; 95% confidence interval: 1.9-2.3) or be admitted to a HCF (odds ratio = 3.4; 95% confidence interval: 3.0-3.7) than 6 to 19-year-olds. The most common scenarios were "inadvertently taken or given medication twice" (53.9%), followed by "inadvertently taken or given someone else's medication" (13.4%), and "wrong medication taken or given" (12.9%).

CONCLUSIONS

The frequency of cases reported to poison centers of pediatric out-of-hospital therapeutic errors related to ADHD medications increased by almost 300% during the 22-year study period and is likely attributable to increased prescribing of these medications. Because therapeutic errors are preventable, more attention should be given to patient and caregiver education and development of improved child-resistant medication dispensing and tracking systems.

An updated safety review of the current drugs for managing ADHD in children

INTRODUCTION

Attention-Deficit/Hyperactivity Disorder (ADHD) is a highly prevalent condition that causes persistent problems with attention and/or hyperactivity-impulsivity and often results in significant impairment when left untreated. Medications for this disorder continue to evolve and provide new treatment options. Ongoing review of related medication safety and tolerability remains an important task for prescribers.

AREAS COVERED

This manuscript provides an updated safety review of medications used to treat ADHD in children and adolescents. PubMed and OneSearch online databases were utilized to search for literature relevant to the topic of ADHD medications and safety. Clinical trials of medications used to treat ADHD, systematic reviews and meta-analyses, and articles covering specific safety issues (adverse or unfavorable events) such as cardiovascular effects, seizures, impact on growth, depression, suicidal ideation, substance use disorders, psychosis, and tics are described.

EXPERT OPINION

Available pharmacologic treatments for ADHD have favorable efficacy, safety and tolerability and allow many patients to achieve significant improvement of their symptoms. Despite the availability of multiple stimulant and non-stimulant formulations, some individuals with ADHD may not tolerate available medications or attain satisfactory improvement. To satisfy unmet clinical needs, ADHD pharmaceutical research with stimulant and nonstimulant formulations targeting dopamine, norepinephrine, and novel receptors is ongoing.

Methylphenidate Multiphasic Release Tablet: Bioequivalence Assessment between Two Formulations Administered under Fasting and Fed Conditions

Methylphenidate hydrochloride is used to treat children, adolescents, and adults with attention deficit/hyperactivity disorder (ADHD). Multiphasic release formulation has been used to control drug levels, mainly during children's school period. This study aimed to evaluate the bioequivalence between two methylphenidate hydrochloride extended-release tablets to meet regulatory requirements for registration in Brazil. Two independent studies (under fasting and fed conditions) designed as open-label, randomized, single-dose, two-period, two-way crossover trials were conducted in healthy subjects of both genders. Subjects were enrolled and randomly received a single dose of the test formulation methylphenidate hydrochloride 54 mg extended-release tablet (Consiv^®, Adium S.A., São Paulo, Brazil) or the reference formulation (Concerta^®, Janssen-Cilag Farmacêutica Ltd., São Paulo, Brazil), in each period, with a 7-day washout interval. Serial blood samples were collected up to 24 h post dose and methylphenidate plasma concentrations were obtained using a validated LC-MS/MS method. A total of 96 healthy subjects were enrolled in the fasting study, of which 80 completed the study. For the fed study, 52 healthy subjects were enrolled, and 46 subjects completed it. In both studies, 90% confidence intervals for Cmax, AUC_0-t, AUC_0-inf, and partial AUCs were within the acceptable limits of 80.00 to 125.00%. Thus, according to regulatory requirements, the test formulation (Consiv^®) was considered to be bioequivalent to the reference formulation (Concerta^®) in both conditions (fasting and fed) and, therefore, it can be considered interchangeable in clinical practice. Both formulations were safe and well tolerated in single-dose administration.

Evaluating serdexmethylphenidate and dexmethylphenidate capsules as a once-daily treatment option for ADHD

INTRODUCTION

Attention deficit/hyperactivity disorder (ADHD) is a common behavioral disorder which is best treated through a combination of medication and behavioral therapy, with stimulant medications serving as a first-line treatment approach. Serdexmethylphenidate (SDX), a prodrug of dexmethylphenidate (d-MPH), a commonly utilized stimulant medication, has recently received approval and is marketed in the U.S.A.

AREAS COVERED

This review summarizes peer-reviewed literature on SDX published between 2021-2023 and a review of data available from ClinicalTrials.gov.

EXPERT OPINION

SDX represents a new option for treatment for ADHD. It is unique in its prodrug design and achieves a relatively extended duration of action in comparison to other stimulant formulations. Although the research is relatively limited thus far, early data suggests it to be a safe medication to consider with side effects being similar to other stimulant medications. Its prodrug design is useful in potentially serving as a deterrent to intentional parenteral abuse and its ability to be opened and sprinkled makes it an option for those individuals with ADHD who might be unable to swallow pills.

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.

Prediction of Carboxylesterase 1-mediated In Vivo Drug Interaction between Methylphenidate and Cannabinoids using Static and Physiologically Based Pharmacokinetic Models

The use of cannabis products has increased substantially. Cannabis products have been perceived and investigated as potential treatments for attention-deficit/hyperactivity disorder (ADHD). Accordingly, co-administration of cannabis products and methylphenidate (MPH), a first-line medication for ADHD, is possible. Oral MPH undergoes extensive presystemic metabolism by carboxylesterase 1 (CES1), a hepatic enzyme which can be inhibited by two prominent cannabinoids, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). This prompts further investigation into the likelihood of clinical interactions between MPH and these two cannabinoids through CES1 inhibition. In the present study, inhibition parameters were obtained from a human liver S9 system and then incorporated into static and physiologically-based pharmacokinetic (PBPK) models for prediction of potential clinical significance. The inhibition of MPH hydrolysis by THC and CBD was reversible, with estimated unbound inhibition constants (Ki,u) of 0.031 and 0.091 µM, respectively. The static model predicted a mild increase in MPH exposure by concurrent THC (34%) and CBD (94%) from smoking a cannabis cigarette and ingestion of prescriptive CBD, respectively. PBPK models suggested no significant interactions between single doses of MPH and CBD (2.5 - 10 mg/kg) when administered simultaneously, while a mild interaction (area under drug concentration-time curve increased by up to 55% and maximum concentration by up to 45%) is likely if multiple doses of CBD (10 mg/kg twice daily) are administered. In conclusion, the pharmacokinetic disposition of MPH can be potentially influenced by THC and CBD under certain clinical scenarios. Whether the magnitude of predicted interactions translates into clinically relevant outcomes requires verification in an appropriately designed clinical study. SIGNIFICANCE STATEMENT: This work demonstrated a potential mechanism of drug-drug interactions between methylphenidate (MPH) and two major cannabinoids (Δ9-tetrahydrocannabinol [THC] and cannabidiol [CBD]) not previously reported. We predicted a mild interaction between MPH and THC when the cannabinoid exposure occurred via cannabis smoking. Mild interactions between MPH and CBD were predicted with multiple oral administrations of CBD.

Beyond pain control: Outcome and treatment preferences in pediatric migraine

OBJECTIVE

The objective of this study was to describe treatment preferences and perceived quality of existing outcome measures among children and adolescents with migraine and their caregivers.

BACKGROUND

Across disciplines, there is increasing recognition of the value of direct input from stakeholders. Little empirical work has been done to determine what outcomes matter most to pediatric patients with migraine and their caregivers.

METHODS

In this qualitative study, we recruited participants from the multicenter, prospective Pediatric Migraine Registry. We used stratified purposive sampling to recruit children and adolescents of varied ages and headache frequency. Patients with migraine and their caregivers completed semistructured interviews targeting treatment preferences and perceived quality of existing outcome measures. Emergent themes and subthemes were identified using conventional content analysis.

RESULTS

Thirty dyads of children/adolescents and their caregivers were enrolled and completed 59 interviews (n = 29 children/adolescent interviews and n = 30 caregiver interviews). Three themes emerged. (1) Symptom relief: Looking beyond headache resolution: Participants described the value of outcomes in addition to pain relief, including a reduction in migraine intensity and improvement in non-pain symptoms. (2) Trade-offs between side effects and relief: Participants described cost-benefit analyses that can occur with headache treatment and acknowledged the impact of drug side effects on daily life and medication adherence. (3) Child-centered treatment: Participants described medication attributes salient to the pediatric context, including age-appropriate routes of administration and adequate safety data.

CONCLUSIONS

Children, adolescents, and caregivers impacted by migraine value outcomes in addition to traditionally studied migraine endpoints. Participants valued decreased pain severity, even in the absence of pain resolution. Participants also prioritized the absence of side effects and key medication attributes, including fast onset and age-appropriate routes of administration. These results highlight an opportunity to design patient-centered clinical trials, develop drugs, and support product labeling that align with the outcomes valued most by children and adolescents with migraine and their caregivers.

The effects of stimulant dose and dosing strategy on treatment outcomes in attention-deficit/hyperactivity disorder in children and adolescents: a meta-analysis

Clinical guidelines currently recommend practitioners titrate stimulant medications, i.e., methylphenidate (MPH) and amphetamines (AMP), to the dose that maximizes symptom control without eliciting intolerable adverse events (AEs) when treating attention-deficit/hyperactivity disorder (ADHD) in school-aged children/adolescents. However, robust evidence-base regarding the effects of doses and dosing strategies of stimulants on clinical outcomes in the treatment of children/adolescents with ADHD is currently lacking and stimulants are often underdosed in clinical practice. To address this gap and provide rigorous evidence-base in relation to the dose and dosing strategy of stimulants, we conducted the largest systematic review and dose-response meta-analysis examining change in ADHD symptoms (efficacy), and treatment discontinuations due to AEs (tolerability) and any reason (acceptability). We conducted one-stage random-effects dose-response meta-analyses examining MPH and AMP separately, stratifying trials based on fixed-dose and flexible-dose design. Daily doses of stimulants were converted to MPH- and AMP-equivalent doses by adjusting for different pharmacokinetics across formulations. We also conducted pairwise meta-analyses to provide indirect comparisons between flexible-dose versus fixed-dose trials. Our study included 65 RCTs involving 7 877 children/adolescents. Meta-analyses of fixed-dose trials for both MPH and AMP demonstrated increased efficacy and increased likelihood of discontinuation due to AEs with increasing doses of stimulants. The incremental benefits of stimulants in terms of efficacy decreased beyond 30 mg of MPH or 20 mg of AMP in fixed-dosed trials. In contrast, meta-analyses of flexible-dose trials for both MPH and AMP demonstrated increased efficacy and reduced likelihood of discontinuations for any reason with increasing stimulant doses. The incremental benefits of stimulants in terms of efficacy remained constant across the FDA-licensed dose range for MPH and AMP in flexible-dose trials. Our results suggest that flexible titration as needed, i.e., considering the presence of ADHD symptoms, and tolerated, i.e., considering the presence of dose-limiting AEs, to higher doses of stimulants is associated with both improved efficacy and acceptability because practitioners can increase/reduce doses based on control of ADHD symptoms/dose-limiting AEs. Although fixed-dose trials that are required by the FDA are valuable to characterize dose-dependency, they may underestimate the true potential benefit of trialing dose-increases of stimulants in clinical practice by not allowing dose adjustment based on response and tolerability. Additional research is required to investigate potential long-term effects of using high doses of stimulants in clinical practice.

MicroRNAs serve as prediction and treatment-response biomarkers of attention-deficit/hyperactivity disorder and promote the differentiation of neuronal cells by repressing the apoptosis pathway

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder. This study aimed to examine whether miRNA expression abundance in total white blood cells (WBCs) facilitated the identification of ADHD and reflected its response to treatment. Furthermore, whether miRNA markers facilitated the growth of the human cortical neuronal (HCN-2) cells was also investigated. Total WBC samples were collected from 145 patients and 83 controls, followed by RNA extraction and qPCR assays. Subsequently, WBC samples were also collected at the endpoint from ADHD patients who had undergone 12 months of methylphenidate treatment. The determined ΔCt values of 12 miRNAs were applied to develop an ADHD prediction model and to estimate the correlation with treatment response. The prediction model applying the ΔCt values of 12 examined miRNAs (using machine learning algorithm) demonstrated good validity in discriminating ADHD patients from controls (sensitivity: 96%; specificity: 94.2%). Among the 92 ADHD patients completing the 12-month follow-up, miR-140-3p, miR-27a-3p, miR-486-5p, and miR-151-5p showed differential trends of ΔCt values between treatment responders and non-responders. In addition, the in vitro cell model revealed that miR-140-3p and miR-126-5p promoted the differentiation of HCN-2 cells by enhancing the length of neurons and the number of junctions. Microarray and flow cytometry assays confirmed that this promotion was achieved by repressing apoptosis and/or necrosis. The findings of this study suggest that the expression levels of miRNAs have the potential to serve as both diagnostic and therapeutic biomarkers for ADHD. The possible biological mechanisms of these biomarker miRNAs in ADHD pathophysiology were also clarified.

Predictors of Changes in Height, Weight, and Body Mass Index After Initiation of Central Nervous System Stimulants in Children with Attention Deficit Hyperactivity Disorder

OBJECTIVE

To identify predictors of changes in height, weight, and body mass index (BMI) in children with attention deficit hyperactivity disorder (ADHD) starting central nervous system (CNS) stimulants.

STUDY DESIGN

There were 230 medication-naïve children aged 5-12 years with ADHD who participated in a randomized trial evaluating the impact of CNS stimulants on growth over 30 months. This observational analysis focused on the 141 participants using study medication for 65 or more days in the first 6-months after starting medication. Biometric variables, ADHD, and oppositional defiant disorder symptom scores at medication initiation, and medication use over the study were examined as predictors of changes in standardized (z) height, weight, and BMI.

RESULTS

Mean changes in z-BMI, z-weight. and z-height were negative throughout the study. The most consistent predictors of change in z-BMI, z-weight, and z-height were percent days medicated and total medication exposure. Children with lower z-height and z-weight at medication initiation experienced greater z-BMI and z-weight decreases over the first 6 months on medication. Greater appetite suppression during dose optimization predicted greater decreases in z-weight over the entire study and a greater decrease in z-height over the first 6 months on medication. z-weight change correlated with z-height change. Behavioral symptoms did not predict changes in z-BMI, z-weight, or z-height.

CONCLUSIONS

How much and how often CNS stimulants are used predicts changes in z-BMI, z-weight, and z-height in children. Even smaller and lighter children may be at risk for decreases in z-weight and z-BMI. Parent ratings of appetite during dose titration may serve as feasible indicators of future weight and height change in children using CNS stimulants.

TRIAL REGISTRATION

Clinicialtrials.gov: NCT01109849.

Neural Markers of Methylphenidate Response in Children With Attention Deficit Hyperactivity Disorder

Background

Despite widespread use of stimulants to treat ADHD, individual responses vary considerably and few predictors of response have been identified. The identification of reliable and clinically feasible biomarkers would facilitate a precision medicine approach to pharmacological treatment of ADHD. We test the hypothesis that two electroencephalography (EEG) based neural signatures of ADHD, resting aperiodic slope exponent and novelty P3 amplitude, are markers of methylphenidate response in children. We hypothesize that positive response to methylphenidate treatment will be associated with greater abnormality of both neural markers.

Methods

Twenty-nine 7-11 year-old children with ADHD and a history of methylphenidate treatment, and 30 controls completed resting EEG and visual oddball event related potential (ERP) paradigms. ADHD participants were characterized as methylphenidate responders (n = 16) or non-responders (n = 13) using the clinical global improvement (CGI-I) scale during blinded retrospective interview. All participants abstained from prescribed medications for at least 48 hours prior to the EEG.

Results

As expected, methylphenidate responders (CGI-I rating < 3) demonstrated attenuated P3 amplitude relative to controls. Unexpectedly, methylphenidate non-responders showed atypically flat aperiodic spectral slope relative to controls, while responders did not differ on this measure.

Conclusion

ADHD symptoms associated with atypical patterns of intrinsic neural activity may be less responsive to methylphenidate. In contrast, ADHD symptoms associated with abnormal frontal-striatal neural network excitation may be correctable with methylphenidate. Altogether, EEG is a feasible and promising candidate methodology for identifying biomarkers of stimulant response.

Evidence-based pharmacological treatment options for ADHD in children and adolescents

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity, causing functional impairment. Its prevalence lies at approximately 5% in children and adolescents and at approximately 2.5% in adults. The disorder follows a multifactorial etiology and shows a high heritability. Patients show a high interindividual and intraindividual variability of symptoms, with executive deficits in several cognitive domains. Overall, ADHD is associated with high rates of psychiatric comorbidities, and insufficient treatment is linked to adverse long-term outcomes. Current clinical guidelines recommend an individualized multimodal treatment approach including psychoeducation, pharmacological interventions, and non-pharmacological interventions. Available medications include stimulants (methylphenidate, amphetamines) and non-stimulants (atomoxetine, guanfacine, clonidine). While available pharmacological treatment options for ADHD show relatively large effect sizes (in short-term trials) and overall good tolerability, there is still a need for improvement of current pharmacotherapeutic strategies and for the development of novel medications. This review summarizes available pharmacological treatment options for ADHD in children and adolescents, identifies current issues in research and evidence gaps, and provides an overview of ongoing efforts to develop new medications for the treatment of ADHD in children and adolescents by means of a systematic cross-sectional analysis of the clinical trials registry www.clinicaltrials.gov.

Effectiveness and safety of dexamphetamine sulfate (Attentin®) in the routine treatment of children and adolescents with ADHD: results from a 12-month non-interventional study

Background

Randomized controlled trials have shown that dexamphetamine sulfate (DEX) is efficacious in the treatment of attention-deficit/hyperactivity disorder (ADHD) in children and adolescents; however, data on the effectiveness and safety of DEX in routine practice are scarce.

Objective

This study investigated the long-term effectiveness and safety of Attentin^® (immediate-release DEX) in children and adolescents with ADHD in routine practice.

Methods

ATTENTION was a multicenter, prospective, observational, non-interventional study that enrolled pediatric patients with ADHD (aged 6-17 years) with a clinically inadequate response to previous methylphenidate (MPH) treatment. Patients were assessed at baseline and two follow-up visits after approx. 6 and 12 months of DEX treatment. The primary endpoint was the investigator-rated ADHD rating scale IV (ADHD-RS-IV) total score change from baseline to the first follow-up visit.

Results

The study enrolled 140 patients (mean age: 11.2 years). Significant reductions in ADHD-RS-IV total scores were observed in the titration phase and were maintained up to the second follow-up visit. The mean ADHD-RS-IV total score change from baseline to the first follow-up visit was -11.9 (27.1 vs. 13.4, p < .001). Beneficial effects of DEX were observed on both ADHD-RS-IV subscales ('hyperactivity/impulsivity' and 'inattention') and in both children and adolescents. Clinical response, defined as a reduction in the ADHD-RS-IV total score of at least 30% at the first follow-up visit, was observed in 78.1% of patients. Patients reported an average onset of action of 36.2 minutes and an average duration of action of 6.5 hours after intake of the first dose of DEX in the morning. DEX was well tolerated. Small significant increases in mean systolic and diastolic blood pressure compared to baseline were observed.

Conclusions

Attentin^® is an effective and well-tolerated long-term treatment for pediatric ADHD patients with a clinically inadequate response to previous MPH treatment.

Update on methylphenidate and dexmethylphenidate formulations for children with attention-deficit/hyperactivity disorder

PURPOSE

Current literature on the safety and efficacy of intermediate- and long-acting formulations of methylphenidate and dexmethylphenidate for attention-deficit/hyperactivity disorder (ADHD) is evaluated.

SUMMARY

Methylphenidate has been an established treatment for ADHD, but due to its relatively short half-life, numerous intermediate- and long-acting products have been developed. While these extended-release products provide efficacy similar to that of immediate-acting products, the pharmacokinetics and adverse effects can vary. Intermediate-acting methylphenidate products have effects that can last as long as 8 hours, but clinically patients have still required twice-daily dosing. Long-acting products have helped to address these challenges, with recently developed products including controlled-release and bimodal-delivery systems and a patch formulation. Many of these products can be opened and sprinkled on applesauce for ease of administration.

CONCLUSION

Knowledge of the various formulations of methylphenidate and dexmethylphenidate is crucial for appropriate medication selection for control of ADHD symptoms. Knowledge of differences between release mechanisms and the pharmacokinetic properties are essential for appropriate use of these products.

Reviewing the role of emerging therapies in the ADHD armamentarium

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder that can be treated with both pharmacologic and nonpharmacologic modalities. Effective drug treatments for ADHD have been available for more than six decades. However, initial treatments had limitations in duration of effect, need for multiple daily doses, requirement for patients to swallow intact tablets, adverse effects and risk for abuse and diversion. During the past 20 years, more than two dozen stimulant and nonstimulant drugs have been developed. Nonetheless, there remain unmet needs in the treatment of ADHD.Areas covered: New stimulant and nonstimulant formulations in development are reviewed with emphasis on drugs in phase II and III trials. Efficacy, mechanism of action and adverse effect data are described where available. Abuse liability studies are described for abuse-deterrent formulations in development.Expert opinion: The review found a robust pipeline of stimulants and nonstimulants. Medications in development are formulated to optimize onset and duration of effect, alter the time of administration, obviate the need to swallow whole capsules or tablets and to deter abuse. While each of these formulations may fill a unique niche, these incremental improvements based on new drug delivery technologies may lead to very significant clinical effects.

Genetic Influence on Efficacy of Pharmacotherapy for Pediatric Attention-Deficit/Hyperactivity Disorder: Overview and Current Status of Research

Multiple stimulant and non-stimulant medications are approved for the treatment of attention-deficit/hyperactivity disorder (ADHD), one of the most prevalent childhood neurodevelopmental disorders. Choosing among the available agents and determining the most effective ADHD medication for a given child can be a time-consuming process due to the high inter-individual variability in treatment efficacy. As a result, there is growing interest in identifying predictors of ADHD medication response in children through the burgeoning field of pharmacogenomics. This article reviews childhood ADHD pharmacogenomics efficacy studies published during the last decade (2009-2019), which have largely focused on pharmacodynamic candidate gene investigations of methylphenidate and atomoxetine response, with a smaller number investigating pharmacokinetic candidate genes and genome-wide approaches. Findings from studies which have advanced the field of ADHD pharmacogenomics through investigation of meta-analytic approaches and gene-gene interactions are also overviewed. Despite recent progress, no one genetic variant or currently available pharmacogenomics test has demonstrated clinical utility in pinpointing the optimal ADHD medication for a given individual patient, highlighting the need for further investigation.

A Pharmacokinetic Study of Methylphenidate Hydrochloride Multilayer Extended-Release Capsules (Aptensio XR®) in Preschool-Aged Children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

This was a single-dose, one-period, multicenter, pharmacokinetic (PK) study to evaluate the PK of methylphenidate (MPH) hydrochloride multilayer extended-release capsules (MPH-MLR) in preschool children aged 4 to < 6 years, previously diagnosed with attention-deficit/hyperactivity disorder (ADHD), and on a stable dose of MPH.

METHODS

Preschool-aged children (N = 10) received a single oral dose of MPH-MLR (10, 15, or 20 mg) sprinkled over applesauce; a dose equivalent to their pre-enrollment daily dose of MPH. Blood samples for the measurement of MPH concentrations were obtained pre-dose and at 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 24 h post-dose. No structural model was assumed in the derivation of PK values for analysis. Maximum plasma concentration (C_max), area under the concentration-time curve (AUC), elimination half-life, clearance (CL), and volume of distribution (V_d) data were compared with a historical group of older children aged 6-11 years (N = 11) and analyzed by bodyweight. Safety (adverse event monitoring, vital signs, electrocardiogram, clinical laboratory testing, physical examination) was assessed.

RESULTS

Mean dose-normalized C_max and area under the curve to the last measurable observation (AUC_0-t) values were similar across dose groups, ranging from 0.67 ng/mL/mg (MPH 15 mg) to 0.81 ng/mL/mg (MPH 10 mg) for C_max/dose, and from 7.80 h × ng/mL/mg (MPH 20 mg) to 8.92 h × ng/mL/mg (MPH 10 mg) for AUC_0-t/dose. PK results were integrated into a previously described pharmacostatistical population PK model. Visual predictive check plots showed greater variability in the 6- to 11-year-old group than the 4- to < 6-year-old group, and CL increased with increasing body weight in a greater than dose-proportional manner. Mean CL, normalized for body weight, was constant for all dose groups, ranging from 4.88 L/h/kg to 5.80 L/h/kg. Median time to C_max ranged from 2.00 to 3.00 h post-dose, and overall, dose-normalized C_max concentrations indicated greater systemic exposures of MPH-MLR in preschool children aged 4 to < 6 years compared with children aged 6-11 years. Children aged 4 to < 6 years had a lower V_d than children aged 6-11 years. There were no unexpected safety signals.

CONCLUSION

The PK of MPH-MLR in preschool children demonstrated the biphasic absorption profile described earlier in older children, and the PK profile in children with ADHD aged 4 to < 6 years was similar to the profile in those aged 6-11 years, apart from a lower V_d and relatively higher systemic MPH levels for children in the preschool group.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT02470234.

An update on the pharmacokinetic considerations in the treatment of ADHD with long-acting methylphenidate and amphetamine formulations

Introduction: Long-acting stimulant formulations are recommended as first-line pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD). Over the past 20 years, extended-release (ER) methylphenidate (MPH) and amphetamine (AMP) formulations have evolved to include varying drug delivery technologies, enantiomers/salts, and dosage forms. All formulations are characterized by a unique pharmacokinetic profile that is closely mirrored by pharmacodynamic response allowing clinicians to individualize therapy based on their patient's clinical needs and dosing preferences.Areas covered: This review provides an update on the pharmacokinetic properties of approved and investigational ER MPH and AMP formulations and highlights pharmacokinetic features that clinicians should consider when selecting a long-acting stimulant.Expert opinion: Since there are no reliable biomarkers that can predict individualized response to long-acting stimulants, clinicians need to consider their distinctive pharmacokinetic properties, including the pharmacokinetic profile, rate and extent of absorption, variability, dose proportionality, bioequivalence, and potential for accumulation. Clinicians also need to understand that certain factors can contribute to increased variability in pharmacokinetics and potentially affect outcomes. Less invasive, high-throughput techniques and novel time-based scales are being developed to advance research on the pharmacokinetic-pharmacodynamic relationships of stimulants. Model-based pharmacokinetic-pharmacodynamic approaches can be applied to aid the development of novel formulations and individualize therapy with existing drugs.