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In the last 15 years, there has been a marked increase in the number of available stimulant formulations with the emphasis on long-acting formulations, and the introduction of several novel delivery systems such as orally dissolving tablets, chewable tablets, extended-release liquid formulations, transdermal patches, and novel "beaded" technology. All of these formulations involve changes to the pharmaceutical delivery systems of the two existing compounds most commonly employed to treat attention-deficit/hyperactivity disorder (ADHD), amphetamine (AMP) and methylphenidate (MPH). In addition to these new formulations, our knowledge about the individual differences in response has advanced and contributes to a more nuanced approach to treatment. The clinician can now make increasingly informed choices about these formulations and more effectively individualize treatment in a way that had not been possible before. In the absence of reliable biomarkers that can predict individualized response to ADHD treatment, clinical knowledge about differences in MPH and AMP pharmacodynamics, pharmacokinetics, and metabolism can be utilized to personalize treatment and optimize response. Different properties of these new formulations (delivery modality, onset of action, duration of response, safety, and tolerability) will most likely weigh heavily into the clinician's choice of formulation. To manage the broad range of options that are now available, clinicians should familiarize themselves in each of these categories for both stimulant compounds. This review is meant to serve as an update and a guide to newer stimulant formulations and includes a brief review of ADHD and stimulant properties.

Attention deficit/hyperactivity disorder (ADHD) symptoms are common in youth with autism spectrum disorders (ASD) and are frequently treated with stimulant medications. Twenty-seven children were randomized to different dose titration schedules, and ADHD symptoms, tolerability, and aberrant behaviors were assessed weekly during a 6-week trial with long-acting liquid methylphenidate (MPH). MPH at low to moderate doses was effective in reducing ADHD symptoms and was well tolerated in young children with ASD and ADHD. Future studies are needed to assess generalization and maintenance of efficacy.

Objective: Methylphenidate has prominent effects in the dopamine-rich striatum that are absent for the selective norepinephrine transporter inhibitor atomoxetine. This study tested whether baseline striatal activation would predict differential response to the two medications in youth with attention-deficit/hyperactivity disorder (ADHD)., Method: A total of 36 youth with ADHD performed a Go/No-Go test during functional magnetic resonance imaging at baseline and were treated with methylphenidate and atomoxetine using a randomized cross-over design. Whole-brain task-related activation was regressed on clinical response., Results: Task-related activation in right caudate nucleus was predicted by an interaction of clinical responses to methylphenidate and atomoxetine (F 1,30  = 17.00; p < .001). Elevated caudate activation was associated with robust improvement for methylphenidate and little improvement for atomoxetine. The rate of robust response was higher for methylphenidate than for atomoxetine in youth with high (94.4% vs. 38.8%; p = .003; number needed to treat = 2, 95% CI = 1.31-3.73) but not low (33.3% vs. 50.0%; p = .375) caudate activation. Furthermore, response to atomoxetine predicted motor cortex activation (F 1,30  = 14.99; p < .001)., Conclusion: Enhanced caudate activation for response inhibition may be a candidate biomarker of superior response to methylphenidate over atomoxetine in youth with ADHD, purportedly reflecting the dopaminergic effects of methylphenidate but not atomoxetine in the striatum, whereas motor cortex activation may predict response to atomoxetine. These data do not yet translate directly to the clinical setting, but the approach is potentially important for informing future research and illustrates that it may be possible to predict differential treatment response using a biomarker-driven approach., Clinical Trial Registration Information: Stimulant Versus Nonstimulant Medication for Attention Deficit Hyperactivity Disorder in Children; https://clinicaltrials.gov/; NCT00183391., (Copyright © 2017 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.)

Objective: The purpose of this study was to compare the short-term efficacy, tolerability, and 1-year adherence in Chinese children and adolescents with attention-deficit/hyperactivity disorder (ADHD) treated with either osmotic release oral system methylphenidate (OROS MPH) or atomoxetine (ATX)., Methods: Children and adolescents meeting Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV) criteria for ADHD were randomly assigned to receive either OROS MPH (n = 119) or ATX (n = 118). Participants underwent a 1-4 week dose titration period to determine optimal dose, and then were maintained on that dose for 4 weeks (maintenance period). Assessment for efficacy was conducted every week over the titration period and at the end of the maintenance period. The primary efficacy measure was the investigator-rated total ADHD Rating Scale-IV (ADHD-RS-IV) score. Response was further classified as remission (ADHD-RS-IV [18 or 9 items] average score ≤1), robust improvement (ADHD-RS-IV ≥40% decrease in total score), or improvement (≥ 25% decrease in total score) at the end of maintenance period. Medication adherence (taking medication at least 5 days in 1 week) and reasons for nonadherence were evaluated every week over the titration period, at the end of maintenance period, and then at 3, 6, and 12 months., Results: At the end of maintenance period, both OROS MPH and ATX were associated with significant and similar reductions from baseline in ADHD symptoms. Percentages achieving remission, robust improvement, and improvement were comparable for OROS MPH and ATX treatment (35.3% vs. 37.1%, 45.4% vs. 44.8%, 65.5% vs. 66.4%). Medication use decreased over time for both treatments; however, at end of maintenance period, 3 month, 6 month, and 1 year follow-ups, subjects in the OROS MPH group were more likely to be compliant with treatment (74.8%, 50.4%, 38.7%, and 21.8% for OROS MPH vs. 52.5%, 33.9%, 12.7%, and 3.4% for ATX) ( p < 0.05). The most common reasons for nonadherence were adverse events and lack of efficacy., Conclusions: Both OROS MPH and ATX resulted in similar reductions in ADHD symptoms in Chinese children and adolescents with ADHD. Long-term adherence with medication was poor in general, although somewhat better with OROS MPH than with ATX., Clinical Trial Registration: ClinicalTrials.gov , Identifier: NCT01065259.

Background: This study examined the effects of atomoxetine (ATX) and OROS methylphenidate (MPH) on laboratory measures of inhibitory control and attention in youth with attention-deficit/hyperactivity disorder (ADHD). It was hypothesized that performance would be improved by both treatments, but response profiles would differ because the medications work via different mechanisms., Methods: One hundred and two youth (77 male; mean age = 10.5 ± 2.7 years) with ADHD received ATX (1.4 ± 0.5 mg/kg) and MPH (52.4 ± 16.6 mg) in a randomized, double-blind, crossover design. Medication was titrated in 4-6-week blocks separated by a 2-week placebo washout. Inhibitory control and attention measures were obtained at baseline, following washout, and at the end of each treatment using Conners' Continuous Performance Test II (CPT-II), which provided age-adjusted T-scores for reaction time (RT), reaction time variability (RT variability), and errors. Repeated-measures analyses of variance were performed, with Time (premedication, postmedication) and Treatment type (ATX, MPH) entered as within-subject factors. Data from the two treatment blocks were checked for order effects and combined if order effects were not present., Clinical Trial Registration: Clinicaltrials.gov: NCT00183391., Results: Main effects for Time on RT (p = .03), RTSD (p = .001), and omission errors (p = .01) were significant. A significant Drug × Time interaction indicated that MPH improved RT, RTSD, and omission errors more than ATX (p < .05). Changes in performance with treatment did not correlate with changes in ADHD symptoms., Conclusions: MPH has greater effects than ATX on CPT measures of sustained attention in youth with ADHD. However, the dissociation of cognitive and behavioral change with treatment indicates that CPT measures cannot be considered proxies for symptomatic improvement. Further research on the dissociation of cognitive and behavioral endpoints for ADHD is indicated., (© 2014 The Authors. Journal of Child Psychology and Psychiatry. © 2014 Association for Child and Adolescent Mental Health.)

Objective: To compare the dose effects of long-acting extended-release dexmethylphenidate (ER d-MPH) and ER mixed amphetamine salts (ER MAS) on attention-deficit/hyperactivity disorder (ADHD) symptom dimensions, global and specific impairments, and common adverse events associated with stimulants., Methods: Fifty-six children and adolescents with ADHD participated in an 8-week, double-blind, crossover study comparing ER d-MPH (10, 20, 25-30 mg) and ER MAS (10, 20, 25-30) with a week of randomized placebo within each drug period. Efficacy was assessed with the ADHD Rating Scale-IV (ADHD-RS-IV), whereas global and specific domains of impairment were assessed with the Clinical Global Impressions Severity and Improvement Scales and the parent-completed Weiss Functional Impairment Scale, respectively. Insomnia and decreased appetite, common stimulant-related adverse events, were measured with the parent-completed Stimulant Side Effects Rating Scale., Results: Both ER d-MPH and ER MAS were associated with significant reductions in ADHD symptoms. Improvement in Total ADHD and Hyperactivity/Impulsivity symptoms were strongly associated with increasing dose, whereas improvements in Inattentive symptoms were only moderately associated with dose. About 80% demonstrated reliable change on ADHD-RS-IV at the highest dose level of ER MAS compared with 79% when receiving ER d-MPH. Decreased appetite and insomnia were more common at higher dose levels for both stimulants. Approximately 43% of the responders were preferential responders to only one of the stimulant formulations., Conclusions: Dose level, rather than stimulant class, was strongly related to medication response.

Objective: Because of significant individual variability in attention-deficit/hyperactivity disorder (ADHD) medication response, there is increasing interest in identifying genetic predictors of treatment effects. This study examined the role of four catecholamine-related candidate genes in moderating methylphenidate (MPH) dose-response., Method: Eighty-nine stimulant-naive children with ADHD 7 to 11 years old participated in a randomized, double-blind, crossover trial of long-acting MPH. Parents and teachers assessed each child's response on placebo and three MPH dosage levels using the Vanderbilt ADHD rating scales. Children were genotyped for polymorphisms in the 3' untranslated region of dopamine transporter (DAT), exon 3 on dopamine receptor D(4) (DRD4), codon 158 on catechol-O-methyltransferase, and the adrenergic α(2A)-receptor promoter. Linear mixed models evaluated gene, dose (milligrams per kilogram per day), and gene-by-dose effects on inattentive and hyperactive-impulsive domain outcomes., Results: The most statistically significant gene-by-dose interactions were observed on hyperactive-impulsive symptoms for DRD4 and DAT polymorphisms, with participants lacking the DAT 10-repeat allele showing greater improvements in symptoms with increasing dose compared with 10-repeat carriers (p = .008) and those lacking the DRD4 4-repeat allele showing less improvement across MPH doses compared with 4-repeat carriers (p = 0.02)., Conclusions: This study suggests that DAT and DRD4 polymorphisms may be associated with individual variability in MPH dose-response, although further research in larger samples is required to confirm these findings and their clinical utility., Clinical Trial Registration Information: Response Variability in Children with Attention-Deficit/Hyperactivity Disorder (ADHD); http://www.clinicaltrials.gov; NCT01238822., (Copyright © 2011 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.)

Objective: The aim of this study was to evaluate dose-response characteristics in adolescents with attention-deficit/hyperactivity disorder (ADHD) treated with once-daily OROS methylphenidate (OROS MPH) during the 4-week, open-label, escalating dose-titration phase of a larger multisite, placebo-controlled trial. Patient factors such as age, height, weight, and baseline symptom severity were evaluated as predictors of selected dose, as was the degree of incremental response with each successive dose escalation., Methods: Adolescents 13-18 years of age with ADHD underwent a 4-week, open-label, escalating dose-titration trial to determine the minimal effective dose (18, 36, 54, or 72 mg once daily) of OROS to be used in a multiphase, placebo-controlled study (NCT00249353). Both final absolute dose and mean weight-adjusted dose were used to assess predictors of response, using a one-way analysis of variance and regression analyses., Results: The majority of subjects who did not respond at lower doses achieved response at each escalating dose level. Approximately two-thirds of subjects required a dose of 54 mg or greater to achieve improvement criteria. Minimal effective dose correlated modestly with baseline symptom severity. Age, height, and weight did not correlate with absolute dose and accounted for only a small percentage of variance in weight-based dose. Weight was not a major factor in predicting effective dose; however, using weight-adjusted rather than absolute dose proved slightly superior for modeling of adverse effects., Conclusions: Adolescents required, on average, a higher absolute dose but a lower weight-adjusted dose (mg/kg) of OROS) than was previously reported in children. There were few predictors of optimal dose of OROS other than baseline symptom severity. The increased percentage of adolescent responders at each dose level using this clinically driven approach to titration differs from recent findings from randomized forced dose titration studies in adults with ADHD.

The dopamine transporter locus (DAT1) has been studied as a risk factor for attention-deficit/hyperactivity disorder (ADHD) and in pharmacogenetic studies of stimulant response. Several prospective studies have reported an association between the homozygous 9 repeat allele of the DAT1 3' untranslated region (UTR) variable number tandem repeat (VNTR) (DAT1 3') and decreased efficacy of methylphenidate (MPH). We hypothesized that children with the 9/9 genotype would display higher rates of specific stimulant side effects. Data on adverse events and DAT1 3' genotypes were combined from two, double-blind, placebo-controlled, crossover studies of MPH conducted in child psychiatric outpatient clinics in Montreal and Washington, D.C. There were 177 participants, 5-16 years old (mean age = 8.99, standard deviation [SD] = 2), with ADHD. Parents completed the Stimulant Side Effect Scale (SERS) after a week of placebo and a week of MPH treatment. Principal components analysis of the SERS resulted in three factors: Emotionality, Somatic Complaints, and Over-focused. Children with the 9/9 genotype displayed higher scores on the Emotionality factor during placebo than children with the 9/10 and the 10/10 genotype, and their Emotionality scores increased further during MPH treatment (F[2,151] = 3.24, p < 0.05). Children with the 10/10 genotype displayed a significant increase in Somatic Complaint factor scores during MPH treatment relative to the other genotype groups (F[2,150] = 3.4, p < 0.05). These data provide suggestive evidence that DAT1 variants are differentially associated with specific stimulant side effects. Children with the 9/10 genotype displayed less severe stimulant side-effect ratings than either of the homozygous groups, who each displayed increased susceptibility to different types of adverse events. Preliminary evidence suggests that pharmacogenetic analysis using DAT1 variants shows promise for identifying individuals at increased or decreased risk for poor tolerability.

Several studies have evaluated the association between individual polymorphisms and response to methylphenidate (MPH) in subjects with attention-deficit/hyperactivity disorder (ADHD). There are few replication studies for each polymorphism of interest and results are sometimes inconsistent in this field. Although data collection from multiple international sites would allow large sample sizes, this approach has been criticized for introducing sampling variability due to differences in ethnicity and methodology between studies. To examine these issues, we aggregated nine pharmacogenetic studies from four different continents and conducted a two stage analysis: (a) we evaluated the role of methodological aspects in the variability of ADHD symptom improvement between studies using meta-regression analysis; (b) we assessed the role of individual characteristics of the subjects in the variability of ADHD symptoms improvement using multivariate regression analysis in the same data sets. At the study level, from five evaluated factors, only the design of the study (open studies vs. randomized controlled trials) was significantly associated with heterogeneity of results (P = 0.001). At the individual level, age (P < 0.001), comorbid oppositional defiant disorder (P < 0.001), and pre-treatment scores (P < 0.001) were associated with change of ADHD scores with treatment in the final multivariate model. Our results suggest that joint analyses of pharmacogenetic studies are feasible and promising, since fixed variables, such as the site where the study was conducted, were not related to results. Nevertheless, stratified analyses according to the design of the study must be preferentially conducted and the role of individual factors such as demographic data and comorbid profile as confounders should be assessed., (Copyright 2008 Wiley-Liss, Inc.)

Objective: A preliminary study to examine the efficacy of osmotic-release oral system (OROS) methylphenidate for attention-deficit/hyperactivity disorder (ADHD) symptoms and parenting behaviors in mothers with ADHD who had children with ADHD., Method: Participants included 23 mother-child dyads in which both were diagnosed with DSM-IV ADHD. Mothers underwent a 5-week, double-blind titration (placebo, 36 mg/day, 54 mg/day, 72 mg/day, 90 mg/day) to an optimal dose of OROS methylphenidate, followed by random assignment to 2 weeks of placebo or their maximally effective dose. Primary outcome measures included maternal ADHD symptoms (Conners' Adult ADHD Rating Scale) and parenting (Alabama Parenting Questionnaire). Secondary outcomes included side effects ratings. Data were collected from December 2004 until August 2006., Results: During Phase 1, mothers reported significant decreases in inattention (p < .001) and hyperactivity/impulsivity (p < .01) with increases in OROS methylphenidate dose. As dose increased, significant reductions in inconsistent discipline (p < .01) and corporal punishment use (p < .005) were also demonstrated. During Phase 2, small effects on inattention (d = 0.46) and hyperactivity/impulsivity (d = 0.38) were found for those randomly assigned to medication versus placebo. In addition, medium to large medication effects were found on maternal involvement (d = 0.52), poor monitoring/supervision (d = 0.70), and inconsistent discipline (d = 0.71), with small effects on corporal punishment (d = 0.42). During both phases, few adverse effects were noted., Conclusions: OROS methylphenidate was well tolerated and was associated with significant improvement in maternal ADHD symptoms and parenting. Variable effects on parenting suggest that behavioral interventions may be necessary to address impairments in parenting among adults with ADHD., Trial Registration: clinicaltrials.gov Identifier: NCT00318981., (Copyright 2008 Physicians Postgraduate Press, Inc.)

Background: Despite the persistence of attention-deficit/hyperactivity disorder (ADHD) into adolescence, little is known about the efficacy and tolerability of stimulant medications in this age group., Objective: To report the results of a multisite controlled study among adolescents with ADHD evaluating the efficacy and tolerability of osmotic-release oral system (OROS) methylphenidate., Design: Adolescents (N = 220) having a confirmed Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnosis of ADHD underwent dose titration to identify dosages of OROS methylphenidate that improved symptoms to predefined criteria. Subjects successfully completing the dose titration phase (n = 177) (ie, tolerated and responded to treatment and adhered to the protocol) were randomized to receive 2 weeks' treatment with their individualized dosage of OROS methylphenidate (18, 36, 54, or 72 mg once daily) or placebo. Treatment effectiveness was measured using investigator, parent, and adolescent assessments of ADHD., Results: A significant reduction from baseline in the investigator-rated ADHD Rating Scale, the primary efficacy measure, was found with OROS methylphenidate treatment compared with placebo. Similar findings were noted with parent- and adolescent-report measures. Based on a Clinical Global Impression improvement subscale score of much or very much improved, 52% of subjects in the OROS methylphenidate group improved compared with 31% receiving placebo. Thirty-seven percent of subjects required the maximum dosage of 72 mg/d. The incidence of drug-related adverse events was similar between the 2 study groups., Conclusion: In adolescents, once-daily OROS methylphenidate significantly reduced ADHD symptoms and was well tolerated using dosages up to 72 mg/d.

Stimulant medications, such as methylphenidate (MPH), are the most commonly used, effective treatment for ADHD. MPH acts primarily by inhibiting the dopamine transporter (DAT), a protein responsible for the reuptake of dopamine from the synapse into presynaptic terminals. We sought to evaluate the relationship between DAT1 3'-untranslated region (3'-UTR) variable number tandem repeats (VNTR) genotypes and dose response to MPH. Children with ADHD (n=47), ages 5-16 years (mean=9.02 years), underwent a 4-week, double-blinded, crossover trial with forced weekly dosage changes. Children were genotyped for the DAT1 VNTR and evaluated on placebo and three dosage levels of OROS MPH. Parents and clinicians who were blind to genotype and medication status rated ADHD symptoms, impairment, and stimulant side effects each week. Children who were homozygous for the less common, 9-repeat DAT1 3'-UTR genotype displayed a distinct dose-response curve from that of the other genotype groups, with an absence of typical linear improvement when the dose was increased from 18 mg to 36 and 54 mg. Further research is needed to determine the mechanisms related to poor response in patients with the 9/9-repeat genotype, and to determine if this group responds differentially to alternative treatments.

Objective: OROS methylphenidate HCL (MPH) is a recently developed long-acting stimulant medication used to treat attention-deficit/hyperactivity disorder (ADHD). This study was conducted to examine dosage effects on ADHD symptoms and stimulant side effects and to explore potential moderating effects of ADHD subtype., Methods: Children with ADHD combined type (ADHD-CT) or predominantly inattentive type (ADHD-PI; n = 47), ages 5 to 16 years, underwent a placebo-controlled, crossover trial using forced titration with weekly switches at 3 dosage levels. Parent and teacher ratings of ADHD symptoms were used to evaluate efficacy. In addition, vital signs and standardized measures of stimulant side effects were obtained weekly., Results: Parent ratings were more sensitive to treatment effects than teacher ratings. ADHD symptoms and Clinical Global Impressions Severity Index ratings at each dose condition differed significantly from placebo and baseline ratings, which did not differ from one another. For those with ADHD-CT, there was a clear linear dose-response relationship, with clinically significant reductions in ADHD Rating Scale-IV scores occurring in two thirds to three fourths of the subjects during either 36- or 54-mg dose conditions. Children with ADHD-PI, conversely, were more likely to respond optimally to lower doses and derived less benefit from higher doses, with 60% displaying significant improvement on the ADHD Rating Scale-IV at 36 mg or lower. Mild stimulant side effects were reported during placebo and at all dosage levels. With the exception of insomnia and decreased appetite, which were more common at higher doses, parent report of side effects was not related to dose. In addition, younger and smaller children were more likely to display sleep difficulties and decreased appetite at the higher dose levels Although pulse rate increased slightly with increasing dose, there were no dose effects on blood pressure., Conclusions: In children with ADHD-CT, the most common subtype of ADHD, increasing doses of stimulant medication were associated with increased improvement of inattention and hyperactivity symptoms. In children with ADHD-PI, symptom improvement occurred at lower doses and less benefit was derived from higher doses. In both ADHD subtypes, higher doses were associated with parent ratings of increased insomnia and decreased appetite.