The Challenge of Predicting Which Children with Attention Deficit-Hyperactivity Disorder Will Respond Positively to Methylphenidate

Improving Methylphenidate Titration in Children with Attention-Deficit/Hyperactivity Disorder (ADHD): A Randomized Controlled Trial Using Placebo-Controlled Titration Implemented in Clinical Practice

BACKGROUND AND OBJECTIVES

Concerns exist regarding the rising use of methylphenidate. A double-blind, placebo-controlled methylphenidate titration (PCT) for children with attention-deficit/hyperactivity disorder (ADHD) has shown potential to improve titration (i.e., detection of placebo responders and larger ADHD symptom improvement) in experimental settings. This study aims to determine if these advantages can be transferred to clinical settings.

METHOD

Children (aged 5-13 years) with an ADHD diagnosis and an indication to start methylphenidate (MPH) treatment were recruited. Participants were randomized to PCT or care as usual (CAU) in a 1:1 ratio followed by a 7-week randomized controlled trial (T1) and 6-month, naturalistic, open-label follow-up (T2). Parents, teachers, and physicians rated ADHD symptoms, ADHD medication use, MPH dosing, and treatment satisfaction using questionnaires.

RESULTS

A total of 100 children were enrolled and randomized to PCT (n = 49) or CAU (n = 51). In the PCT group, we found 8.2% placebo responders, 16.3% non-responders, and 65.3% responders to MPH. With PCT compared with CAU, a significantly larger number of children discontinued MPH (T1: 24.5 vs 5.9%, p = 0.009; T2: 41.7 vs 10.4%, p < 0.001) and refrained from using other pharmacological treatment (T1: 20.4 vs 3.9%, p = 0.013; T2: 20.83 vs 6.25%, p = 0.002). At both timepoints, there were no significant differences between the groups in the average dose of MPH, ADHD symptoms, or treatment satisfaction.

CONCLUSIONS

PCT can be used to improve detection of children who do not benefit from MPH, and may therefore potentially reduce overtreatment of ADHD with MPH.

Methylphenidate dose-response in children with ADHD: evidence from a double-blind, randomized placebo-controlled titration trial

Methylphenidate (MPH) is highly efficacious in reducing symptoms of attention-deficit/hyperactivity disorder (ADHD) in children. Generally increased doses are found to result in better symptom control; however, it remains unclear whether this pattern can be observed at the individual level, given the large heterogeneity in individual dose-response relationships and observed placebo responses. A double-blind, randomized, placebo-controlled cross-over trial was used to compare weekly treatment with placebo and 5, 10, 15 and 20 mg of MPH twice daily on parent and teacher ratings of child ADHD symptoms and side effects. Participants were 5-13-year-old children with a DSM-5 diagnosis of ADHD (N = 45). MPH response was assessed at group and individual levels and predictors of individual dose-response curves were examined. Mixed model analysis showed positive linear dose-response curves at group level for parent and teacher rated ADHD symptoms and parent rated side effects, but not for teacher rated side effects. Teachers reported all dosages to improve ADHD symptoms compared to placebo, while parents only reported > 5 mg/dose as effective. At the individual level, most (73-88%) children, but not all, showed positive linear dose-response curves. Higher severity of hyperactive-impulsive symptoms and lower internalizing problems, lower weight, younger age and more positive opinions towards diagnosis and medication partly predicted steeper linear individual dose-response curves. Our study confirms that increased doses of MPH yield greater symptom control at a group level. However, large interindividual variation in the dose-response relationship was found and increased doses did not lead to greater symptom improvement for all children. This trial was registered in the Netherlands trial register (# NL8121).

Predicting the Response of Children and Adolescents With ADHD to Methylphenidate: A Systematic Review

OBJECTIVE

To report the characteristics associated with response to methylphenidate (MPH) in children and adolescents with ADHD.

METHODS

Studies reporting potentials predictors of response to MPH were searched in Medline and Embase from January 1998 to March 2022. Narrative synthesis was performed.

RESULTS

Fifty-seven reports of 46 studies totaling 6,656 ADHD patients were included. No association appears between response to MPH and age, gender, MPH dosage, ADHD subtype, comorbidities nor socioeconomic status when considering a specific patient. No conclusion could be drawn about body weight, ADHD severity, intelligence quotient, and parental symptoms of depression or ADHD.

CONCLUSIONS

None of these potential predictors have proven their usefulness to predict response to MPH on an individual basis in clinical practice. In research, potential predictors should be measured, their association with response to MPH assessed, in order to control for confounding variables when modeling response to MPH.

Meta-analysis: Dose-Dependent Effects of Methylphenidate on Neurocognitive Functioning in Children With Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Neurocognitive deficits are at the heart of explanatory models of attention-deficit/hyperactivity disorder (ADHD), and lead to significant impairments in daily life. Determining the dosing effects of methylphenidate (MPH) on a broad range of neurocognitive functions and investigating possible impairing effects of high doses is therefore important.

METHOD

Placebo-controlled trials were included that investigated MPH dosing effects on neurocognitive functions in children and adolescents (aged 5-18 years) diagnosed with ADHD. Effect sizes (standardized mean differences [SMDs]) were calculated for different neurocognitive functions (baseline speed, variability in responding, nonexecutive memory and executive memory, inhibitory control, and cognitive flexibility) and, if available, for ADHD symptoms. Meta-regression analysis were used to investigate linear effects of dose (mg/kg/dose), and separate meta-analyses compared SMDs for 3 MPH dose ranges: low (0.10-0.30 mg/kg/dose), medium (0.31-0.60 mg/kg/dose), and high (0.61-1.00 mg/kg/dose).

RESULTS

A total of 31 studies fulfilled inclusion criteria, comprising 804 children with ADHD. Methylphenidate had beneficial effects on all neurocognitive functions (d = 0.20-0.73). Significant linear dosing effects were found for ADHD symptoms and lower-order neurocognitive functions (baseline speed, variability in responding, nonexecutive memory), with greater enhancement of functioning with increasing dose. No dosing effects were found for higher-order neurocognitive functions (executive memory, inhibitory control, and cognitive flexibility). No detrimental effects of MPH were found on any of the investigated functions.

CONCLUSION

Methylphenidate was superior to placebo in improving ADHD symptoms and a broad range of neurocognitive functions; however, effects sizes regarding the effects of dose vary substantially between functions. Our data highlight the importance of considering both neurocognitive and symptomatic aspects of ADHD in clinical practice.

Clinical and Neuropsychological Predictors of Methylphenidate Response in Children and Adolescents with ADHD: A Naturalistic Follow-up Study in a Spanish Sample

BACKGROUND

Methylphenidate (MPH) is the most commonly used medication for Attention-Deficit/Hyperactivity Disorder (ADHD), but to date, there are neither consistent nor sufficient findings on conditions differentiating responsiveness to MPH response in ADHD.

OBJECTIVE

To develop a predictive model of MPH response, using a longitudinal and naturalistic follow-up study, in a Spanish sample of children and adolescents with ADHD.

METHODS

We included all children and adolescents with ADHD treated with MPH in our outpatient Clinic (2005 to 2015), evaluated with the K-SADS interview. We collected ADHD-RS-IV.es and CGI-S scores at baseline and at follow up, and neuropsychological testing (WISC-IV, Continuous Performance Test (CPT-II) & Stroop). Clinical response was defined as >30% reduction from baseline of total ADHD-RS-IV.es score and CGI-S final score of 1 or 2 maintained for the previous 3 months.

RESULTS

We included 518 children and adolescents with ADHD, mean (SD) age of patients was 11.4 (3.3) years old; 79% male; 51.7% had no comorbidities; and 75.31% had clinical response to a mean MPH dose of 1.2 mg/kg/day. Lower ADHD-RS-IV.es scores, absence of comorbidities (oppositional-defiant symptoms, depressive symptoms and alcohol/cannabis use), fewer altered neuropsychological tests, higher total IQ and low commission errors in CPT-II, were significantly associated with a complete clinical response to methylphenidate treatment.

CONCLUSION

Oppositional-defiant symptoms, depressive symptoms, and a higher number of impaired neuropsychological tests are associated with worse clinical response to methylphenidate. Other stimulants or non-stimulants treatment may be considered when these clinical and neuropsychological variables converged in the first clinical interview.

Predictors of Response to Behavioral Treatments Among Children With ADHD-Inattentive Type

The goal of the study was to examine baseline characteristics-child gender, IQ, age, internalizing problems, symptoms of hyperactivity/impulsivity (HI), oppositional defiant disorder, and sluggish cognitive tempo, and parent income, education, attention deficit/hyperactivity disorder (ADHD) severity, and anxiety/depression (A/D)-associated with response to behavioral treatments for ADHD, predominantly inattentive type. We employed data from 148 children (M = 8.7 years), 58% male, and 57% Caucasian in a randomized clinical trial. Positive treatment response was defined as (a) 5 or fewer inattentive symptoms and (b) a decrease of at least 3 inattentive symptoms from baseline to posttreatment. Child HI, parental A/D, and child IQ were associated with positive response, as follows: Child HI had a main effect in which it was negatively associated with treatment response (36% with 2 or more HI symptoms were positive responders vs. 59% of those with 1 or no symptoms) that was qualified by parental A/D and child IQ. When children had 2 or more symptoms of HI and higher parental A/D, positive response rate was low at 25%; when children had 2 or more symptoms of HI, low parental A/D, and an IQ of 105 or higher, positive response rate was 85%. Furthermore, the group with the poorest response rate (25%) had parents who self-reported greater ADHD severity, and the group with a relatively good rate of positive response (59%) had the lowest number of oppositional defiant disorder symptoms. Likelihood of positive response to our behavioral treatment for ADHD-I is dependent on child and parent factors.

Effects of maternal symptom ratings and other clinical features on short-term treatment response to OROS methylphenidate in children and adolescents with ADHD in a naturalistic clinical setting

OBJECTIVE

To investigate the effect of Attention Deficit Hyperactivity Disorder (ADHD), antisocial behavior and anxiety/depression ratings of mothers, and child and adolescents' age, gender, ADHD subtype, and comorbidity on one-month drug treatment response to OROS methylphenidate in ADHD in a naturalistic setting.

METHODS

The analyses included 223 subjects (191 boys, 32 girls; age 6-15 years, mean: 9.4) treated with OROS methylphenidate (18-72 mg/day, mean: 31 mg/d; 0.4-1.4 mg/kg/d) for one-month. Treatment response was defined as larger than 25% or more decrease in pre-treatment the Conners Parent Rating Scale (CPRS) or the Conners Teacher Rating Scale (CTRS) total scores and the Clinical Global Impression improvement with drug treatment 3 (minimally improved) or higher. Maternal ADHD, antisocial behavior and anxiety/depression ratings were obtained by the Adult Self Rating (ASR). Logistic regression analyses were computed in order to calculate the effects of gender; age; ADHD subtype; comorbid anxiety disorder, learning disorder, oppositional defiant/conduct disorder; maternal ASR Anxiety/Depression, ADHD and Antisocial scores.

RESULTS

35.2% of subjects had statistically significant 25% or more decrease in pretreatment CPRS total scores and 38.6% of subjects had statistically significant 25% or more decrease in pretreatment CTRS total scores. The subjects with comorbid anxiety disorder had the poorest drug response. Maternal self-reported antisocial and anxiety/depressive symptomatology were statistically significantly associated with worse response to treatment in terms of CPRS (respectively, OR=0.83, 95% CI: 0.75-0.92, p<0.01; OR=0.95, 95% CI: 0.9-0.99, p<0.05) and CTRS total scores (OR=0.9, 95% CI: 0.82-0.99, OR=0.95, 95% CI: 0.91-1, p<0.05). Baseline rating scores were also important predictors of drug treatment response. Effects of age, gender and maternal ADHD were not statistically significant.

CONCLUSION

ADHD children and adolescents with comorbid anxiety disorders and those whose mothers have more self-reports of antisocial and depressive symptoms showed less favorable short-term response to OROS-MPH. These subjects may require further attention and additional interventions to augment treatment with OROS methylphenidate.

Single-dose effects on the P3no-go ERP component predict clinical response to stimulants in pediatric ADHD

OBJECTIVE

Approximately 30% of children and adolescents diagnosed with attention-deficit/hyperactivity disorder (ADHD) and treated with stimulants are considered non-responders (non-REs). Reliable predictors of response are missing. We examined changes in Event-Related Potentials (ERPs) induced by a single dose of stimulant medication in order to predict later clinical response.

METHODS

ERPs were registered twice during performance of a visual cued go/no-go task in 87 ADHD patients (27 girls) aged 8-18years; the second recording on a single dose of stimulant medication, followed by a systematic medication trial lasting 4weeks. Based on the four-week trial, participants were categorized as responders (REs, N=62) or non-REs (N=25). Changes among REs and non-REs in ERP components (cueP3, CNV, P3go, N2no-go, P3no-go) and behavioral-test variables were then compared.

RESULTS

REs and non-REs differed significantly in medication-induced changes in P3no-go, cue-P3, CNV, omission errors, reaction time, and reaction-time variability. The largest effect size was found for P3no-go amplitude (p<.001; d=1.76). Changes in P3no-go and omission errors correctly classified 90% of the REs and 76% of the non-REs, when controlling for the age of the participants.

CONCLUSION

Clinical response to stimulants can be predicted by assessing single-dose changes in the P3no-go ERP component amplitude.

SIGNIFICANCE

Changes in P3no-go may be a clinically useful marker of response to stimulants.

Reconsidering the concept of behavioral mechanisms of drug action

A half-century of research in behavioral pharmacology leaves little doubt that behavior-environment contingencies can determine the behavioral effects of drugs. Unfortunately, a coherent behavior-analytic framework within which to characterize the myriad ways in which contingencies interact with drugs, and to predict effects of a given drug under a given set of conditions, still has not developed. Some behavioral pharmacologists have suggested the concept of behavioral mechanisms of drug action as a foundation for such a framework. The notion of behavioral mechanisms, however, does not seem to have been fully embraced by behavioral pharmacologists. It is suggested here that one reason for this is that the concept itself has not been sufficiently clarified (i.e., stimulus control over use of the phrase is not sufficiently precise). Furthermore, early behavioral pharmacologists may not have possessed an adequate set of analytic tools to develop a viable framework based upon behavior mechanisms. In the first part of this paper, the notion of behavioral mechanisms of drug action is explored, and the sort of data that might provide evidence of a behavioral mechanism is considered. In the second part, it is suggested that the increased availability of quantitative models in behavior analysis may help provide the tools needed for elucidating behavioral mechanisms of drug action. Some examples of how these models have been, and could be used are provided.

Neuroimaging markers for the prediction of treatment response to Methylphenidate in ADHD

BACKGROUND

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent mental disorders of childhood, which often continues into adulthood. Methylphenidate is one the most commonly used medication to treat ADHD, however up to 30% of patients do not respond to it.

AIMS

This paper aims to review studies, which employed neuroimaging to predict treatment response to Methylphenidate in ADHD.

METHODS

Systematic literature searches were performed using several databases. Selected articles had to describe an original study that identified neuroimaging markers for the prediction of treatment response to Methylphenidate in ADHD.

RESULTS

Eighty-three articles were found, of which twelve were selected for the present review. Several neuroimaging markers to predict response to MPH were suggested including DAT status, size of medial prefrontal cortex and corpus callosum.

CONCLUSION

Some promising findings have been identified and they should motivate additional work to establish more reliable neuroimaging markers of treatment response to MPH in ADHD.

Methylphenidate effects on neural activity during response inhibition in healthy humans

Methylphenidate (MPH) is a catecholamine transporter blocker, with dopamine agonistic effects in the basal ganglia. Response inhibition, error detection, and its mediating frontostriatal brain activation are improved by MPH in patients with attention-deficit/hyperactivity disorder. However, little is known about the effects of MPH on response inhibition and error processing or its underlying brain function in healthy individuals. Therefore, this study employed functional magnetic resonance imaging (fMRI) and 2 response inhibition tasks in 52 healthy males. Subjects underwent fMRI during a go/no-go task and a tracking stop-signal task after administration of 40 mg MPH and placebo in a double-blind, placebo-controlled, repeated-measures design. Results revealed task- and condition-specific neural effects of MPH: it increased activation in the putamen only during inhibition errors but not during successful inhibition and only in the go/no-go task. We speculate that task specificity of the effect might be due to differences in the degree of error saliency in the 2 task designs, whereas errors were few in the go/no-go task and thus had high saliency and the stop-signal task was designed to elicit 50% of errors in all subjects, diminishing the error saliency effect. The findings suggest that neural MPH effects interact with the saliency of the behavior under investigation.

Do phenotypic characteristics, parental psychopathology, family functioning, and environmental stressors have a role in the response to methylphenidate in children with attention-deficit/hyperactivity disorder? A naturalistic study from a developing country

Little is known about the effect of clinical characteristics, parental psychopathology, family functioning, and environmental stressors in the response to methylphenidate in children with attention-deficit/hyperactivity disorder (ADHD) followed up in a naturalistic setting. Data from cultures outside the United States are extremely scarce. This is a longitudinal study using a nonrandom assignment, quasi-experimental design. One hundred twenty-five children with ADHD were treated with methylphenidate according to standard clinical procedures, and followed up for 6 months. The severity of ADHD symptoms was assessed by the Swanson, Nolan, and Pelham rating scale. In the final multivariate model, ADHD combined subtype (P < 0.001) and comorbidity with oppositional defiant disorder (P = 0.03) were both predictors of a worse clinical response. In addition, the levels of maternal ADHD symptoms were also associated with worse prognosis (P < 0.001). In the context of several adverse psychosocial factors assessed, only undesired pregnancy was associated with poorer response to methylphenidate in the final comprehensive model (P = 0.02). Our study provides evidence for the involvement of clinical characteristics, maternal psychopathology, and environmental stressors in the response to methylphenidate. Clinicians may consider adjuvant strategies when negative predictors are present to increase the chances of success with methylphenidate treatment.

Efficacy and tolerability of lisdexamfetamine dimesylate in children with attention-deficit/hyperactivity disorder: sex and age effects and effect size across the day

BACKGROUND

Efficacy and safety profiles by sex and age (6-9 vs 10-12 years) and magnitude and duration of effect by effect size overall and across the day of lisdexamfetamine dimesylate (LDX) vs placebo were assessed.

METHODS

This study enrolled children (6-12 years) with attention-deficit/hyperactivity disorder (ADHD) in an open-label dose optimization with LDX (30-70 mg/d) followed by a randomized, double-blind, placebo-controlled, 2-way crossover phase. Post hoc analyses assessed interaction between sex or age and treatment and assessed effect sizes for Swanson, Kotkin, Agler, M-Flynn, and Pelham (SKAMP) and Permanent Product Measure of Performance (PERMP) scales and ADHD Rating Scale IV measures. No corrections for multiple testing were applied on time points and subgroup statistical comparisons.

RESULTS

129 participants enrolled; 117 randomized. Both sexes showed improvement on all assessments at postdose time points; females showed less impairment than males for SKAMP and PERMP scores in treatment and placebo groups at nearly all times. Both age groups improved on all assessments at postdose time points. Children 10-12 years had less impairment in SKAMP ratings than those 6-9 years. Treatment-by-sex interactions were observed at time points for SKAMP-D, SKAMP total, and PERMP scores; no consistent pattern across scales or time points was observed. LDX demonstrated significant improvement vs placebo, by effect size, on SKAMP-D from 1.5-13 hours postdose. The overall LS mean (SE) SKAMP-D effect size was -1.73 (0.18). In the dose-optimization phase, common (≥2%) treatment-emergent adverse events (TEAEs) in males were upper abdominal pain, headache, affect lability, initial insomnia, and insomnia; in females were nausea and decreased weight. During the crossover phase for those taking LDX, higher incidence (≥2% greater) was observed in males for upper abdominal pain and insomnia and in females for nausea and headache. Overall incidence of TEAEs in age groups was similar.

CONCLUSION

Apparent differences in impairment level between sex and age groups were noted. However, these results support the efficacy of LDX from 1.5 hours to 13 hours postdose in boys and girls with medium to large effect sizes across the day with some variability in TEAE incidence by sex.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT00500149.

The multifaceted effects of oral administration of methylphenidate in juvenile rats: anxiety, activity, and attention

In previous studies, acutely administered oral methylphenidate (MPD, 3mg/kg) prior to testing improved performance on the radial arm maze in juvenile rats. In order to examine the mechanisms producing this improvement we administered MPD once prior to each test of anxiety, locomotor activity and attention. On postnatal day (PND) 22 on an elevated plus maze, rats spent more time beyond the rails on the open arms and showed altered risk-assessment behaviors suggesting an anxiolytic-like effect of MPD. Grid crossings on the plus maze indicated that MPD increased locomotor activity, as did activity recording on PND 23. In another group of juveniles, MPD improved performance in a multi-trial attention task in an age-dependent fashion. These data suggest that oral MPD has multifaceted effects on juvenile rats that together improve performance on cognitive tests such as the radial arm maze. In addition, our data support human studies finding multifaceted effects of MPD.

Behavioral parent training as an adjunct to routine care in children with attention-deficit/hyperactivity disorder: moderators of treatment response

OBJECTIVE

To investigate predictors and moderators of outcome of behavioral parent training (BPT) as adjunct to ongoing routine clinical care (RCC), versus RCC alone.

METHODS

We randomly assigned 94 referred children (4-12 years) with attention-deficit/hyperactivity disorder (ADHD) to BPT plus RCC or RCC alone. Outcome was based on parent-reported behavioral problems and ADHD symptoms. Predictor/moderator variables included children's IQ, age, and comorbidity profile, and maternal ADHD, depression, and parenting self-efficacy.

RESULTS

Superior BPT treatment effects on behavioral problems and ADHD symptoms were present in children with no or single-type comorbidity-anxiety/depression or oppositional defiant disorder (ODD)/conduct disorder (CD)-and when mothers had high parenting self-efficacy, but absent in children with broad comorbidity (anxiety/depression and ODD/CD) and when mothers had low parenting self-efficacy. In older children ADHD symptoms tended to decrease more through BPT than in younger children.

CONCLUSIONS

Adjunctive BPT is most useful when mothers have high parenting self-efficacy and in children with no or single-type comorbidity.

Treatment of attention deficit hyperactivity disorder in children. Predictors of treatment outcome

OBJECTIVE

The present study investigated the predictive power of anxiety, IQ, severity of ADHD and parental depression on the outcome of treatment in children with ADHD.

METHOD

Fifty children with ADHD (ages 8-12) were randomized to a 10-week treatment of methylphenidate or to a treatment of methylphenidate combined with multimodal behavior therapy. Prior to treatment predictors were assessed. Outcome was assessed separately for parents and teachers on a composite measure of inattentive, hyperactive, oppositional- and conduct disorder symptoms.

RESULTS

There was neither a significant difference between the two treatments at baseline nor did treatment condition predict outcome. Therefore the data were collapsed across the two treatments. A combination of anxiety and IQ predicted teacher-rated outcome, explaining 18% of the variance. Higher anxiety and higher IQ's indicated better treatment outcome. There were no significant predictors of the parent-rated outcome.

CONCLUSION

This study showed a small but significant predictive effect of IQ and anxiety on treatment outcome in children with ADHD.

CLINICAL IMPLICATIONS

This study supports the idea that for the treatment of ADHD children with comorbid anxiety and higher IQ respond better to the two most used treatments for ADHD.

The relationship between regional cerebral blood flow and response to methylphenidate in children with attention-deficit hyperactivity disorder: comparison between non-responders to methylphenidate and responders

In a sample of children with attention-deficit hyperactivity disorder (ADHD), a voxel based investigation of regional cerebral blood flow (rCBF) during resting state was conducted to identify functional differences between non-responders to methylphenidate (MPH) and responders. Thirty-four children with ADHD were examined by technetium-99m-hexamethylporphylenamine oxime (HMPAO) SPECT. According to clinical response after 8 weeks of treatment with MPH, they were classified as non-responders to MPH and responders. Using SPM analysis, we compared the SPECT images of non-responders to MPH with those of responders. Non-responders to MPH had higher rCBF in the left anterior cingulate cortex, the left claustrum, the right anterior cingulate cortex, and the right putamen relative to responders. In addition, lower rCBF was found in the right superior parietal lobule in non-responders to MPH relative to responders. Further stepwise discriminant analysis revealed that 88.2% could be correctly classified as either non-responders to MPH or responders when considering the extracted rCBF values in the left anterior cingulate cortex, the left claustrum, and the right superior parietal lobule. The current findings suggest that non-responders to MPH may have different patterns of rCBF in brain regions, which have been known as a part of frontal-striatal circuitry and posterior attentional system, respectively.

Sex differences in the response of children with ADHD to once-daily formulations of methylphenidate

OBJECTIVES

Studies of sex differences in methylphenidate response by children with attention-deficit/hyperactivity disorder have lacked methodological rigor and statistical power. This paper reports an examination of sex differences based on further analysis of data from a comparison of two once-daily methylphenidate formulations (the COMACS study), which addresses these shortcomings.

METHOD

Children (184: 48 females; mean [SD] age, 9.58 [1.83] years) entered a double-blind, crossover trial of Concerta, MetadateCD/Equasym XL, or placebo. Attention-deficit/hyperactivity disorder symptoms were recorded at seven time points across the school day on the seventh day of treatment, using a laboratory classroom setting.

RESULTS

More females had comorbid anxiety disorder. Males and females did not differ with regard to other characteristics. Observed sex differences in pharmacodynamic symptom profiles persisted after controlling for placebo and time 0 hours attention-deficit/hyperactivity disorder scores and the presence of an anxiety disorder. Females had a statistically superior response at 1.5 hours post-dosing and an inferior response at the 12-hour time point relative to their male counterparts, no matter which methylphenidate formulation was being assessed.

CONCLUSIONS

Dose titration of once-daily formulations of methylphenidate should ideally be based on systematic evidence of response at different periods across the day. The responses of female patients may require additional assessments later in the day to determine the optimal dose.

Integrative neuroscience approach to predict ADHD stimulant response

Despite high rates of prescription, little is known about the long-term consequences of stimulant medication therapy for attention-deficit hyperactivity disorder (ADHD) sufferers. Historically, the clinical use of stimulants for ADHD has been based on trial and error before optimal therapy is reached. Concurrently, scientific research on the mechanism of action of stimulants has influenced neurobiological models of ADHD, but has not always informed their prescription. Whilst the two main stimulant types (methylphenidate and dexamphetamine) have numerous similarities, they also differ (slightly) in mechanism and possibly individual response. A further issue relates to differences in cost and availability compounded by the expectation for stimulants to be effective in ameliorating a broad spectrum of ADHD-related symptoms. Thus, there is an increasing need for treating clinicians to prescribe not only the most effective drug, but also the most appropriate dose with the associated release mechanism and schedule for each ADHD patient presented. In this regard, the field is witnessing an emergence of the personalized medicine approach to ADHD, in which treatment decisions are tailored to each individual. This shift requires a new approach to research into treatment response prediction. Given the heterogeneity of ADHD, a profile of information may be required to capture the most sensitive predictors of treatment response in individuals. These profiles will also benefit from the integration of data from clinical rating scales with more direct measures of cognition and brain function. In conclusion, there is a need to establish a more robust normative framework as the baseline for treatment, as well as diagnostic decisions, and as discussed, the growth of integrated neuroscience databases will be important in this regard.

A positron emission tomography study of methylphenidate in adults with ADHD: alterations in resting blood flow and predicting treatment response

A hallmark symptom of attention-deficit hyperactivity disorder (ADHD) is an excess of motoric behavior or hyperactivity. Methylphenidate (MPH) is known to reduce hyperactivity in individuals with ADHD. Yet little is known about how it alters neural activity and how this relates to its clinical effects. The goal of this study is to examine MPH-induced changes during resting brain metabolism, and to examine how these changes correlate with measures of behavioral response to the drug. Measures of regional cerebral blood flow (rCBF) using positron emission tomography (PET) were acquired at rest for ten adult subjects with ADHD during both an unmedicated state and after a 3-week period of chronic dosing with a clinically optimal dose of MPH. Compared with the on-MPH condition, the off-MPH condition was associated with relative increases in rCBF bilaterally in the precentral gyri, left caudate nucleus, and right claustrum. The on-MPH condition was associated with relative increases in rCBF in the cerebellar vermis. A correlational analysis measured the relation between rCBF in the off-medication condition to change in ADHD ratings between the off- and on-MPH condition to identify brain regions associated with treatment response. The degree of change in the ratings was negatively correlated with rCBF increases in the midbrain, cerebellar vermis, and the precentral and middle frontal gyri in the off-MPH condition. The majority of these brain regions are involved in the planning and execution of motor behavior. These data suggest that MPH modulates brain regions associated with motor function to achieve a reduction in ADHD symptoms.