Guidelines and algorithms for the use of methylphenidate in children with Attention-Deficit/ Hyperactivity Disorder

Paternal exposure to a common pharmaceutical (Ritalin) has transgenerational effects on the behaviour of Trinidadian guppies

Evidence is emerging that paternal effects, the nongenetic influence of fathers on their offspring, can be transgenerational, spanning several generations. Methylphenidate hydrochloride (MPH; e.g. Ritalin) is a dopaminergic drug that is highly prescribed to adolescent males for the treatment of Attention-deficit/hyperactivity disorder. It has been suggested that MPH could cause transgenerational effects because MPH can affect the male germline in rodents and because paternal effects have been observed in individuals taking similar drugs (e.g. cocaine). Despite these concerns, the transgenerational effects of paternal MPH exposure are unknown. Therefore, we exposed male and female Trinidadian guppies (Poecilia reticulata) to a low, chronic dose of MPH and observed that MPH affected the anxiety/exploratory behaviour of males, but not females. Because of this male-specific effect, we investigated the transgenerational effects of MPH through the paternal line. We observed behavioural effects of paternal MPH exposure on offspring and great-grandoffspring that were not directly administered the drug, making this the first study to demonstrate that paternal MPH exposure can affect descendants. These effects were not due to differential mortality or fecundity between control and MPH lines. These results highlight the transgenerational potential of MPH.

Effects of the DRD4 -521 C/T SNP on Local Neural Activity and Functional Connectivity in Children With ADHD

Objective: The present study aimed to investigate the effects of the dopamine receptor D4 (DRD4) -521 C/T single-nucleotide polymorphism on brain function among children with attention deficit hyperactivity disorder (ADHD) and to evaluate whether brain function is associated with behavioral performance among this demographic. Methods: Using regional homogeneity, fractional amplitude low-frequency fluctuation, and functional connectivity as measurement indices, we compared differences in resting-state brain function between 34 boys with ADHD in the TT homozygous group and 37 boys with ADHD in the C-allele carrier group. The Conners' Parent Rating Scale, the SNAP-IV Rating Scale, the Stroop Color Word Test, the go/no-go task, the n-back task, and the working memory index within the Wechsler Intelligence Scale for Children-Fourth Edition were selected as comparative indicators in order to test effects on behavioral performance. Results: We found that TT homozygotes had low behavioral performance as compared with C-allele carriers. The regional homogeneity for TT homozygotes decreased in the right middle occipital gyrus and increased in the right superior frontal gyrus as compared with C-allele carriers. In addition, the right middle occipital gyrus and the right superior frontal gyrus were used as the seeds of functional connectivity, and we found that the functional connectivity between the right middle occipital gyrus and the right cerebellum decreased, as did the functional connectivity between the right superior frontal gyrus and the angular gyrus. No statistically significant differences were observed in the respective brain regions when comparing the fractional amplitudes for low-frequency fluctuation between the two groups. Correlation analyses demonstrated that the fractional amplitude low-frequency fluctuation in the precentral gyrus for TT homozygotes were statistically significantly correlated with working memory. Conclusions: We found differing effects of DRD4 -521 C/T polymorphisms on brain function among boys with ADHD. These findings promote our understanding of the genetic basis for neurobiological differences observed among children with ADHD, but they must be confirmed in larger samples.

Moderator Role of Monitoring in the Inhibitory Control of Adolescents With ADHD

Objective: The aim of this research was to analyze the role of monitoring in the causal relationship between inhibitory control and symptoms of combined ADHD. Method: It has been conducted a quantitative investigation of two phases. Results: In the first study, a moderation model was analyzed (N = 144 adolescents with combined ADHD), where monitoring was considered as a moderating variable in the causal relationship between the inhibitory control and the symptomatology of ADHD F(3, 140) = 28.03, p < .001; R² = .37. In the second study, the model through an experimental study was tested (N = 52 adolescents with and without ADHD) where it was found that adolescents with ADHD improve in their inhibitory control when they receive external support to the monitoring F(1, 50) = 21.38, p < .001, η² = .30. Conclusion: Results suggest that monitoring compensates the poor performance of inhibitory control in adolescents with ADHD, which is a contribution to the theoretical construction of ADHD and to the treatments proposed for this condition because it goes beyond the classic conception of a causality chain among the deficit of inhibitory control and ADHD symptomatology to propose a new explanation about this disorder, where neuropsychology intervention of monitoring would diminish ADHD's symptomatology impact on adolescents.

Experimentally altered male mating behaviour affects offspring exploratory behaviour via nongenetic paternal effects

Evidence is emerging that fathers can have nongenetic effects on the phenotypes of their offspring. Most studies have focused on the role that nongenetic modifications to sperm can have on offspring phenotype; however, fathers can also have nongenetic effects on offspring through their interactions with females, called female-mediated paternal effects. These effects can occur in situations where male phenotype, e.g. behaviour or morphology, affects female stress and/or provisioning of offspring. These effects are potentially widespread, but few studies have explicitly investigated the role of female-mediated paternal effects on offspring phenotype. Here, we asked if male mating interactions can affect offspring via female mediated paternal effects in the Trinidadian guppy, Poecilia reticulata. To do this, we manipulated mating behaviour by: (i) administering a drug known to affect the neurotransmitter dopamine, and (ii) varying the familiarity of potential mates, which affects attractiveness in this species. With these treatments, we successfully manipulated the mating behaviour of male guppies and female preference for those males. Further, we found significant effects of sire mating behaviour, sire drug treatment, and parental familiarity status on behavioural measures of offspring anxiety in response to a novel object. Because Control offspring of 'familiar' and 'unfamiliar' pairs differed in their behaviour, our results cannot be solely attributed to potential nongenetic modifications to sperm caused by the drug. These results emphasize the importance of female-mediated paternal effects, including those caused by altered male mating behaviour, in shaping offspring phenotype.

Chronic oral methylphenidate treatment increases microglial activation in rats

Methylphenidate (MP) is a widely prescribed psychostimulant used to treat attention deficit hyperactivity disorder. Previously, we established a drinking paradigm to deliver MP to rats at doses that result in pharmacokinetic profiles similar to treated patients. In the present study, adolescent male rats were assigned to one of three groups: control (water), low-dose MP (LD; 4/10 mg/kg), and high dose MP (HD; 30/60 mg/kg). Following 3 months of treatment, half of the rats in each group were euthanized, and the remaining rats received only water throughout a 1-month-long abstinence phase. In vitro autoradiography using [³H] PK 11195 was performed to measure microglial activation. HD MP rats showed increased [³H] PK 11195 binding compared to control rats in several cerebral cortical areas: primary somatosensory cortex including jaw (68.6%), upper lip (80.1%), barrel field (88.9%), and trunk (78%) regions, forelimb sensorimotor area (87.3%), secondary somatosensory cortex (72.5%), motor cortices 1 (73.2%) and 2 (69.3%), insular cortex (59.9%); as well as subcortical regions including the thalamus (62.9%), globus pallidus (79.4%) and substantia nigra (22.7%). Additionally, HD MP rats showed greater binding compared to LD MP rats in the hippocampus (60.6%), thalamus (59.6%), substantia nigra (38.5%), and motor 2 cortex (55.3%). Following abstinence, HD MP rats showed no significant differences compared to water controls; however, LD MP rats showed increased binding in pre-limbic cortex (78.1%) and ventromedial caudate putamen (113.8%). These findings indicate that chronic MP results in widespread microglial activation immediately after treatment and following the cessation of treatment in some brain regions.

Integrative genomic analysis of methylphenidate response in attention-deficit/hyperactivity disorder

Methylphenidate (MPH) is the most frequently used pharmacological treatment in children with attention-deficit/hyperactivity disorder (ADHD). However, a considerable interindividual variability exists in clinical outcome. Thus, we performed a genome-wide association study of MPH efficacy in 173 ADHD paediatric patients. Although no variant reached genome-wide significance, the set of genes containing single-nucleotide polymorphisms (SNPs) nominally associated with MPH response (P < 0.05) was significantly enriched for candidates previously studied in ADHD or treatment outcome. We prioritised the nominally significant SNPs by functional annotation and expression quantitative trait loci (eQTL) analysis in human brain, and we identified 33 SNPs tagging cis-eQTL in 32 different loci (referred to as eSNPs and eGenes, respectively). Pathway enrichment analyses revealed an over-representation of genes involved in nervous system development and function among the eGenes. Categories related to neurological diseases, psychological disorders and behaviour were also significantly enriched. We subsequently meta-analysed the association with clinical outcome for the 33 eSNPs across the discovery sample and an independent cohort of 189 ADHD adult patients (target sample) and we detected 15 suggestive signals. Following this comprehensive strategy, our results provide a better understanding of the molecular mechanisms implicated in MPH treatment effects and suggest promising candidates that may encourage future studies.

Clinical Implications From the Treatment of Severe Childhood Aggression (TOSCA) Study: A Re-Analysis and Integration of Findings

OBJECTIVE

The Treatment of Severe Childhood Aggression (TOSCA) project examined augmentation of stimulant treatment and parent training (PT) with risperidone for severe physical aggression. This article summarizes the clinical implications; reanalyzes the data to examine the utility of 4 criteria for deciding to augment; and presents a treatment algorithm.

METHOD

The newly analyzed 4 criteria for augmenting after 3 weeks of stimulant and PT treatment consisted of not meeting a Clinical Global Impressions-Improvement (CGI-I) score of 1 and a normal score (≤15) on the Nisonger Child Behavior Rating Form Disruptive-Total (D-Total); a CGI-I score of 1 or 2 plus 25% improvement in D-Total score; a D-Total score no higher than 15; and a CGI-Severity score of 3 (mild) or better. Effect sizes were calculated. Prior TOSCA publications were reviewed for clinically relevant findings.

RESULTS

All 4 criteria resulted in medium or better effect sizes (d = 0.59-0.72) when comparing risperidone with placebo. Providing risperidone to children who did not reach a CGI-I score of 1 plus a D-Total score no higher than 15 resulted in the greatest benefit. In addition, a review of clinically relevant data suggests that stimulant plus PT shows further improvement after 3 weeks even without augmentation.

CONCLUSION

For those children who did not attain a CGI-I score of 1 and a D-total score no higher than 15, adding risperidone maximized the number of children benefitting from treatment and the average amount of benefit. Unless clinical circumstances dictate otherwise, practitioners should delay an antipsychotic drug for at least 1 month after the optimal stimulant dose is achieved and PT has commenced. Clinical trial registration information-Treatment of Severe Childhood Aggression (The TOSCA Study); http://clinicaltrials.gov; NCT00796302.

Pharmacogenetics of methylphenidate in childhood attention-deficit/hyperactivity disorder: long-term effects

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in which a significant proportion of patients do not respond to treatment. The objective of this study was to examine the role of genetic risk variants in the response to treatment with methylphenidate (MPH). The effectiveness of MPH was evaluated based on variations in the CGI-S and CGAS scales over a 12-month treatment period using linear mixed effects models. A total of 208 ADHD patients and 34 polymorphisms were included in the analysis. For both scales, the response was associated with time, extended-release MPH/both formulations, and previous MPH treatment. For the CGI-S scale, response was associated with SLC6A3 rs2550948, DRD4 promoter duplication, SNAP25 rs3746544, and ADGRL3 rs1868790. Interactions between the response over time and SLC6A3 and DRD2 were found in the CGI-S and CGAS scales, respectively. The proportion of the variance explained by the models was 18% for the CGI-S and 22% for the CGAS. In this long-term study, the effects of SLC6A3, DRD4, SNAP25, and ADGRL3 on response to treatment reflect those observed in previous studies. In addition, 2 previously unreported interactions with response to treatment over a 12-month period were found (SLC6A3 and DRD2).

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.

Reduced pain perception in children and adolescents with ADHD is normalized by methylphenidate

BACKGROUND

The present study examined pain perception in children and adolescents with ADHD and the interaction between pain perception and the administration of methylphenidate (MPH) in order to generate hypotheses for further research that will help to clarify the association between ADHD diagnosis, MPH treatment and pain perception.

METHODS

We included 260 children and adolescents of the "German Health Interview and Examination Survey for Children and Adolescents" (KiGGS) and analyzed parent's assessments of children's pain distribution and pain perception, as well as the influence of MPH administration on pain perception in affected children and adolescents.

RESULTS

Pain perception was associated with ADHD and MPH administration, indicating that children and adolescents suffering from ADHD without MPH treatment were reported to have lower pain perception compared to both, healthy controls (HC) and ADHD patients medicated with MPH.

CONCLUSION

We suggest that reduced pain perception in children and adolescents with ADHD not medicated with MPH may lead to higher risk tolerance by misjudgments of dangerous situations, expanding the importance of MPH administration in affected children and adolescents.

The Association of SNAP25 Gene Polymorphisms in Attention Deficit/Hyperactivity Disorder: a Systematic Review and Meta-Analysis

Attention deficit/hyperactivity disorder (ADHD) is one of the most highly heritable psychiatric disorders in childhood. The risk gene mutation accounts for about 60 to 90 % cases. Synaptosomal-associated protein of 25 kDa (SNAP-25) is a presynaptic plasma membrane protein which is expressed highly and specifically in the neuronal cells. A number of evidences have suggested the role of SNAP-25 in the etiology of ADHD. Notably, the animal model of coloboma mouse mutant bears a ∼2-cM deletion encompassing genes including SNAP25 and displays spontaneous hyperkinetic behavior. Previous investigators have reported association between SNPs in SNAP25 and ADHD, and controversial results were observed. In this study, we analyzed the possible association between six polymorphisms (rs3746544, rs363006, rs1051312, rs8636, rs362549, and rs362998) of SNAP25 and ADHD in a pooled sample of ten family-based studies and four case-control studies by using meta-analysis. The combined analysis results were significant only for rs3746544 (P = 0.010) with mild association (odds ratio (OR) = 1.14). And, the meta-analysis data for rs8636, rs362549, and rs362998 are the first time to be reported; however, no positive association was detected. In conclusion, we report some evidence supporting the association of SNAP25 to ADHD. Future research should emphasize genome-wide association studies in more specific subgroups and larger independent samples.

Pharmacological Management of Pediatric Patients with Comorbid Attention-Deficit Hyperactivity Disorder Oppositional Defiant Disorder

Attention-deficit hyperactivity disorder (ADHD) is a common developmental neurobiological condition of childhood characterized by age-inappropriate degrees of hyperactivity/impulsivity and inattention to tasks requiring sustained vigilance. Oppositional defiant disorder (ODD) is an externalizing behavior disorder characterized by difficulties with emotional and behavioral regulation that frequently brings the child into conflict with authority figures. In the clinical setting, ODD is the most common ADHD comorbidity. The combination portends more severe symptom severity, daily impairment, and a more at-risk prognosis than either disorder alone. We briefly review the literature on the characteristics and treatment of the ADHD and ODD child. A clinical approach to evaluation and treatment of ADHD and ODD is then presented. This approach emphasizes the importance of child and parent psychoeducation about the two disorders alone and in combination, the importance of behavioral management therapy approaches, the possible need for school and academic supports, and the decision to use evidence-based stimulant or non-stimulant ADHD medications depending on symptom severity combined with child and parental wishes and choice.

Pharmacologic treatments for the behavioral symptoms associated with autism spectrum disorders across the lifespan

This review outlines pharmacologic treatments for the behavioral symptoms associated with autism spectrum disorders (ASDs) in children, adolescents, and adults. Symptom domains include repetitive and stereotyped behaviors, irritability and aggression, hyperactivity and inattention, and social impairment. Medications covered include serotonin reuptake inhibitors (SRIs), mirtazapine, antipsychotics, psychostimulants, atomoxetine, α-2 agonists, D-cycloserine, and memantine. Overall, SRIs are less efficacious and more poorly tolerated in children with ASDs than in adults. Antipsychotics are the most efficacious drugs for the treatment of irritability in ASDs, and may be useful in the treatment of other symptoms. Psychostimulants demonstrate some benefit for the treatment of hyperactivity and inattention in individuals with ASDs, but are less efficacious and associated with more adverse effects compared with individuals with ADHD. D-cycloserine and memantine appear helpful in the treatment of social impairment, although further research is needed.

Improving working memory in children with attention-deficit/hyperactivity disorder: the separate and combined effects of incentives and stimulant medication

Working memory (WM) is considered a core deficit in Attention-Deficit/ Hyperactivity Disorder (ADHD), with numerous studies demonstrating impaired WM among children with ADHD. We tested the degree to which WM in children with ADHD was improved by performance-based incentives, an analog of behavioral intervention. In two studies, WM performance was assessed using a visuo-spatial n-back task. Study 1 compared children (ages 9-12 years) with ADHD-Combined type (n = 24) to a group of typically developing (TD) children (n = 32). Study 1 replicated WM deficits among children with ADHD. Incentives improved WM, particularly among children with ADHD. The provision of incentives reduced the ADHD-control group difference by approximately half but did not normalize WM. Study 2 examined the separate and combined effects of incentives and stimulant medication among 17 children with ADHD-Combined type. Both incentives and a moderate dose of long-acting methylphenidate (MPH; ~0.3 mg/kg t.i.d. equivalent) robustly improved WM relative to the no-incentive, placebo condition. The combination of incentives and medication improved WM significantly more than either incentives or MPH alone. These studies indicate that contingencies markedly improve WM among children with ADHD-Combined type, with effect sizes comparable to a moderate dose of stimulant medication. More broadly, this work calls attention to the role of motivation in studying cognitive deficits in ADHD and in testing multifactorial models of ADHD.

Drug therapy of attention deficit hyperactivity disorder: current trends

Attention deficit hyperactivity disorder is a developmental disorder with an age onset prior to 7 years. Children with ADHD have significantly lower ability to focus and sustain attention and also score higher on impulsivity and hyperactivity. Stimulants, such as methylphenidate, have remained the mainstay of ADHD treatment for decades with evidence supporting their use. However, recent years have seen emergence of newer drugs and drug delivery systems, like osmotic release oral systems and transdermal patches, to mention a few. The use of nonstimulant drugs like atomoxetine and various other drugs, such as α-agonists, and a few antidepressants, being used in an off-label manner, have added to the pharmacotherapy of ADHD. This review discusses current trends in drug therapy of ADHD and highlights the promise pharmacogenomics may hold in the future.

Long-term effects of chronic oral Ritalin administration on cognitive and neural development in adolescent wistar kyoto rats

The diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) often results in chronic treatment with psychostimulants such as methylphenidate (MPH, Ritalin^®). With increases in misdiagnosis of ADHD, children may be inappropriately exposed to chronic psychostimulant treatment during development. The aim of this study was to assess the effect of chronic Ritalin treatment on cognitive and neural development in misdiagnosed “normal” (Wistar Kyoto, WKY) rats and in Spontaneously Hypertensive Rats (SHR), a model of ADHD. Adolescent male animals were treated for four weeks with oral Ritalin^® (2 × 2 mg/kg/day) or distilled water (dH₂O). The effect of chronic treatment on delayed reinforcement tasks (DRT) and tyrosine hydroxylase immunoreactivity (TH-ir) in the prefrontal cortex was assessed. Two weeks following chronic treatment, WKY rats previously exposed to MPH chose the delayed reinforcer significantly less than the dH₂O treated controls in both the DRT and extinction task. MPH treatment did not significantly alter cognitive performance in the SHR. TH-ir in the infralimbic cortex was significantly altered by age and behavioural experience in WKY and SHR, however this effect was not evident in WKY rats treated with MPH. These results suggest that chronic treatment with MPH throughout adolescence in “normal” WKY rats increased impulsive choice and altered catecholamine development when compared to vehicle controls.

When does it end? Attention-deficit/hyperactivity disorder in the middle aged and older populations

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is estimated to affect 4% to 6% of the adult population. In recent years, more and more middle-aged and older adults (>55 years) turn to the ADHD unit at Geha Mental Health Center suspecting ADHD. Yet, a literature search resulted in very few relevant studies.

METHODS AND RESULTS

This study, approved by the Geha Mental Health Center ethics committee, presents 11 patients, 55 years or older, diagnosed and treated by the unit. The patients underwent complete clinical evaluation for ADHD according to Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition. The data-collection phase included demographic and clinical data; Test of Variables of Attention scores used as indicators of methylphenidate (MPH) response; Clinical Global Impression scores of both severity and improvement were used. Because the sample is very small, allowing only limited statistical analyses, nonparametric statistics were used. Eleven patients, aged 61.64 ± 3.87 years (male-female ratio, 9:2), were assessed. The follow-up was conducted for more than 2 months. Fifty-five percent had ADHD, predominantly inattentive, and 45% had ADHD combined type. All patients indicated suffering (Clinical Global Impression-Severity score range: mild = 27.3%, moderate = 45.4%, severe = 27.3%). Fifty-four percent showed at least 1 psychiatric comorbidity. Test of Variables of Attention scores showed significant improvement in 90% (8/9 patients) with MPH dosages similar to those used in younger adults. All patients attended the follow-up visits. Ninety-one percent (10/11) continued with the medication. Clinical Global Impression-Improvement scores showed significant improvement in 73%. No adverse effects were reported.

CONCLUSIONS

This pilot study described 11 adults 55 years or older, diagnosed with ADHD for the first time. Attention-deficit/hyperactivity disorder characteristics seemed to persevere; middle aged or older ADHD patients had similar clinical-demographic characteristics and a similar response to MPH as younger adults. No significant adverse effects were noted.

Antidepressants and psychostimulants in pediatric populations: is there an association with mania?

This article reviews the literature that examines whether exposure to psychostimulants or antidepressants precipitates or exacerbates manic symptoms, or decreases the age at onset of mania in pediatric populations. A PubMed search using relevant key words identified studies targeting five distinct clinical groups: (i) youth without a diagnosis of bipolar disorder (BD) at the time of exposure to psychostimulants; (ii) youth with a diagnosis of BD at the time of exposure to psychostimulants; (iii) youth without a diagnosis of BD at the time of exposure to antidepressants; (iv) youth with a diagnosis of BD at the time of exposure to antidepressants; and (v) youth who develop BD after exposure to these medications. In patients with attention-deficit hyperactivity disorder (ADHD), the risk for mania was found to be relatively low with the use of psychostimulants. For patients with BD and ADHD, effective mood stabilization is important prior to adding a stimulant. For children with depression and/or anxiety, the risk of antidepressant-induced mania (AIM) was generally low (<2%), but the risk of general 'activation' secondary to a selective serotonin reuptake inhibitor (SSRI) may be greater (2-10%). However, rates of AIM in specialty clinics appear to be much higher. SSRIs may be particularly problematic in specific populations, such as those with some symptoms of mania or a family history of BD, but the precise risk is unknown. There is no clear evidence that stimulants or SSRIs accelerate the natural course of BD development in overall samples, but in individual cases prescribers should proceed cautiously when using these agents in youth already at risk for developing BD, such as those with ADHD and mood dysregulation, a history of prior AIM, a history of psychosis, or a family history of BD.

A randomized, single-blind, substitution study of OROS methylphenidate (Concerta) in ADHD adults receiving immediate release methylphenidate

OBJECTIVE

The main aim of this study was to examine the efficacy, tolerability, and compliance of an extended-release formulation of methylphenidate (OROS-MPH) in adults with ADHD receiving immediate-release methylphenidate (IR-MPH).

METHOD

Participants were outpatient adults with ADHD who were stable on IR-MPH-administered TID. Participants were randomized (4:1) to equipotent doses of OROS-MPH or to continue IR-MPH and were assessed weekly for 6 weeks with the Adult ADHD Investigator System Symptom Report Scale (AISRS).

RESULTS

Randomization of 53 IR-MPH responders to IR- or OROS-MPH had no effect on AISRS score at endpoint (11.2 ± 6.9 vs. 10.7 ± 5.1, p = .8). Participants stabilized on IR-MPH and switched to OROS-MPH remained satisfied over 71% of the time. However, the IR-MPH group missed more doses (7.3 ± 6.8 vs. 3.3 ± 4.2, p = .02) than the OROS-MPH group.

CONCLUSION

Findings showed that adults with ADHD can be successfully switched from an effective regimen of IR-MPH TID to once-daily OROS-MPH. Results also demonstrated better compliance with OROS-MPH than with IR-MPH treatment.

Adrenergic α2A receptor gene is not associated with methylphenidate response in adults with ADHD

Adrenergic α2A receptor gene (ADRA2A) is one of the most promising candidate genes for ADHD pharmacogenetics. Thus far, three studies have investigated the association between the ADRA2A -1291 C>G polymorphism and the therapeutic response to methylphenidate (MPH) in children with ADHD, all of them with positive results. The aim of this study is to investigate, for the first time, the association between three ADRA2A polymorphisms (-1291 C>G, -262 G>A, and 1780 C>T) and the response to MPH in adults with ADHD. The sample comprises 165 Brazilians of European descent evaluated in the adult ADHD outpatient clinic of the Hospital de Clínicas de Porto Alegre. The diagnostic procedures followed the DSM-IV criteria. Drug response was assessed by both categorical and dimensional approaches, through the scales Swanson, Nolan, and Pelham Rating scale version IV and the Clinical Global Impression-Severity Scale, applied at the beginning and after the 30th day of treatment. We found no evidence of association between the three ADRA2A polymorphisms and the therapeutic response to MPH treatment. Our findings do not support a significant role for the ADRA2A gene in ADHD pharmacogenetics, at least among adult patients.

Binding of [123I]iodobenzamide to the rat D2 receptor after challenge with various doses of methylphenidate: an in vivo imaging study with dedicated small animal SPECT

PURPOSE

The effect of various doses of methylphenidate on the binding of [(123)I]iodobenzamide ([(123)I]IBZM) to the rat D(2) receptor was assessed using small animal SPECT.

METHODS

D(2) receptor binding was measured at baseline and after pretreatment with various doses of methylphenidate. For baseline and methylphenidate challenge, striatal equilibrium ratios (V(3)″) were computed as an estimation of the binding potential.

RESULTS

After methylphenidate, striatal V(3)″ was 1.61 ± 0.61 (mean ± SD; 0.3 mg/kg), 0.91 ± 0.44 (3 mg/kg), 1.01 ± 0.44 (10 mg/kg), 0.91 ± 0.34 (30 mg/kg) and 0.99 ± 0.51 (60 mg/kg). Baseline values amounted to 1.73 ± 0.48, 1.32 ± 0.35, 1.50 ± 0.27, 1.82 ± 0.55 and 1.66 ± 0.41, respectively. Differences between baseline and methylphenidate were significant for the doses 3, 10, 30 and 60 mg/kg, whereas no significant difference was obtained for 0.3 mg/kg methylphenidate. Between-group differences of percentage reduction of D(2) receptor binding were only significant for the groups pretreated with 0.3 and 30 mg/kg methylphenidate, respectively.

CONCLUSION

Methylphenidate between 0.3 and 60 mg/kg decreased D(2) receptor binding with a maximum reduction after 30 mg/kg. As no between-group differences were evident between the groups pretreated with 3, 10, 30 and 60 mg/kg, it may be inferred that doses ≥ 3 mg/kg were sufficient to induce maximum dopamine concentration in the synaptic cleft. Further investigations are needed in order to clarify whether the variation between subjects can be accounted for by different synaptic mechanisms at the presynaptic binding site.

Dopaminergic and noradrenergic contributions to functionality in ADHD: the role of methylphenidate

Attention Deficit Hyperactivity Disorder (ADHD) is a childhood psychiatric condition characterized by severe impulsiveness, inattention and overactivity. Methylphenidate (MPH), a psychostimulant affecting both the dopaminergic and the noradrenergic systems, is one of the most frequently prescribed treatments for ADHD. Despite the widespread use of MPH and its proven effectiveness, its precise neurochemical mechanisms of action are under debate. For the most part, MPH’s influence on subcortical dopamine neurotransmission is thought to play a crucial role in its behavioral and cognitive effects. In their hypothesis of biphasic MPH action, Seeman and Madras [42, 43] suggest that therapeutic doses of MPH elevate tonic dopamine while inhibiting phasic transmitter release in subcortical structures, leading to reduced postsynaptic receptor stimulation and psychomotor activation in response to salient stimuli. Volkow and colleagues [56] suggest that by amplifying a weak striatal dopamine signal, MPH increases the perception of a stimulus or task as salient. The enhanced interest for the task is thought to increase attention and improve performance. Recent animal studies have however shown that when administered at doses producing clinically relevant drug plasma levels and enhancing cognitive function, MPH preferentially activates dopamine and noradrenaline efflux within the prefrontal cortex relative to the subcortical structures [5]. Overall, we suggest that the delineated theories of MPH therapeutic action should not be discussed as exclusive. Studies are outlined that allow integrating the different findings and models.

Dose-response characteristics in adolescents with attention-deficit/hyperactivity disorder treated with OROS methylphenidate in a 4-week, open-label, dose-titration study

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.

Are attention lapses related to d-amphetamine liking?

RATIONALE

A rich literature suggests that both impulsiveness and drug-induced euphoria are risk factors for drug abuse. However, few studies have examined whether sensitivity to the euphoric effects of stimulants is related to attention lapses, a behavioral measure of inattention sometimes associated with impulsivity.

OBJECTIVE

The aim of the study was to examine ratings of d-amphetamine drug liking among individuals with high, moderate, and low attention lapses.

METHODS

Ninety-nine healthy volunteers were divided into three equal-sized groups based on their performance on a measure of lapses of attention. The groups, who exhibited low, medium, and high attention lapses (i.e., long reaction times) on a simple reaction time task, were compared on their subjective responses (i.e., ratings of liking and wanting more drug) after acute doses of d-amphetamine (0, 5, 10, and 20 mg).

RESULTS

Subjects who exhibited high lapses liked 20 mg d-amphetamine less than subjects who exhibited low lapses. These subjects also tended to report smaller increases in "wanting more drug" after d-amphetamine.

CONCLUSION

The findings suggest that participants who exhibit impaired attention may be less sensitive to stimulant-induced euphoria.

Stimulant medication and prefrontal functional connectivity during working memory in ADHD: a preliminary report

OBJECTIVE

Recent theoretical and empirical work suggests that while unmedicated, children with ADHD have a deficit in subcortical processing that leads to greater and more varied prefrontal cortical (PFC) activation, compared to (a) age-matched control participants and (b) their own brain activity while on stimulant medication. This pattern has been described elsewhere as inefficient.

METHOD

Functional magnetic resonance imaging (fMRI) and functional connectivity analyses were used during a working memory task for five female adolescents with ADHD, aged 11 to 17 years, both on and off their usual dose of stimulant medication.

RESULTS

On medication, adolescents with ADHD demonstrated less PFC activation and less functional connectivity between frontal and subcortical regions compared to off medication.

CONCLUSIONS

Because of the small sample size, results are presented as preliminary findings which await replication in a larger sample. However, these findings lend support to the idea that remediation of inefficiencies in PFC function for individuals with ADHD by stimulant medication may be related, in part, to frontal-subcortical connectivity.

InforMatrix for attention deficit hyperactivity disorder

The purpose of this review is to facilitate discussion on drug selection for the treatment of ADHD by using only clinically relevant selection criteria and providing an up-to-date overview. The InforMatrix method was used to select drugs to treat attention deficit hyperactivity disorder (ADHD). The following selection criteria were applied: clinical efficacy, safety, tolerability, ease of use, applicability, and cost. The drugs approved for ADHD in the Netherlands were included in the analysis, namely: atomoxetine, immediate-release methylphenidate, and various formulations of slow-release methylphenidate (Concerta, Equasym and Medikinet). Most studies are of limited quality, duration, and size. In one study, Concerta was more effective than atomoxetine. Although no relevant differences were seen in other comparative studies, the clinical experience with atomoxetine is still limited and unexpected toxicity cannot be excluded; few studies have been published with Equasym and Medikinet. No major differences were seen in general tolerability between the drugs. The ease of use of immediate-release methylphenidate is less than for the other drugs. The acquisition cost of immediate-release methylphenidate is considerably lower than that of the slow-release formulations. Atomoxetine is the most expensive drug. The InforMatrix program is available in an interactive format. It enables the user to judge both the importance of the selection criteria and the properties of each therapeutic option per criterion on the basis of his or her own personal expertise and/or the present document.

Prefrontal cortex Homer expression in an animal model of attention-deficit/hyperactivity disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a pervasive neurobehavioral disorder affecting approximately 5% of children and adolescents and 3% of adults, and the prefrontal cortex (PFC) may play the most critical role in the expression of ADHD. Converging previous studies indicate a potential role of Homer--a scaffolding protein family localized at the postsynaptic density (PSD) of glutamatergic excitatory synapses--in behavioral pathologies associated with neuropsychiatric disorders. Accordingly, we speculate that these Homer isoforms might contribute to the etiology and development of ADHD.

METHOD

We investigated the differential mRNA and protein expressions of several Homer isoforms in the PFC of the spontaneous hypertensive rat/Wistar-Kyoto rats (SHR/WKY), the most frequently used animal model of ADHD, using RT-PCR and western blotting. Furthermore, we examined the effects of methylphenidate (MPH) exposure on the behaviors and the expression of different Homer isoforms in the PFC of SHR, using Làt maze, RT-PCR and western blotting, respectively.

RESULTS

Homer 1a and Homer 2a/b, but not Homer 1b/c, were expressed at a significantly lower levels in the PFC of SHR compared with WKY. MPH exposure decreased the locomotor activity and non-selective attention of SHR, and it up regulated the expression of Homer 1a and Homer 2a/b, but not Homer 1b/c, in the PFC of SHR.

CONCLUSION

It is plausible that Homer 1a and Homer 2a/b may be involved in the etiology and pathogenesis of ADHD. Future work will focus on elucidating the specific mechanisms of Homer 1a and Homer 2a/b in ADHD.

Better efficacy for the osmotic release oral system methylphenidate among poor adherents to immediate-release methylphenidate in the three ADHD subtypes

AIMS

To determine factors for switching to osmotic release oral system methylphenidate (OROS-MPH) among poor adherents to immediate-release methylphenidate (IR-MPH); and to compare the efficacy of OROS-MPH on the three attention-deficit/hyperactivity disorder (ADHD) subtypes in a multi-site prospective observational study in Taiwan.

METHODS

The sample included 240 children with ADHD, aged 6-16 years, who were poor adherents to IR-MPH, 137 of whom were switched to OROS-MPH. The child psychiatrists diagnosed the Diagnostic Statistical Manual of Mental Disorders (4th edition) ADHD subtypes and assessed the medical history, adherence, side-effects, global ADHD severity, and family/school effectiveness. Parents reported their child's behavioral symptoms.

RESULTS

The determinants for an OROS-MPH switch were higher dosage, shorter treatment and thrice-daily administration of IR-MPH, and more severe inattention symptoms. Hyperactivity and oppositional symptoms were greater in the ADHD combined and hyperactive-impulsive subtypes than the inattentive subtype. Switching to OROS-MPH significantly improved behavioral symptoms and family/school measures, and this was most evident in the ADHD-combined group, followed by the ADHD-inattentive group. Inattention influenced not only academic performance, but also overall classroom behaviors and the parent-child relationship, with the latter two also influenced by oppositional symptoms.

CONCLUSIONS

This study suggests better efficacy for the OROS-MPH among poor adherents to IR-MPH; however, its effectiveness varied across the three ADHD subtypes (ClinicalTrials.gov number NCT00460720).

Dopamine-related genotypes and the dose-response effect of methylphenidate on eating in attention-deficit/hyperactivity disorder youths

OBJECTIVE

There are individual differences in the effects of methylphenidate (MPH), a dopamine (DA) transport inhibitor, on appetite in children with attention-deficit/hyperactivity disorder (ADHD). One potential moderating factor is variation in brain DA activity, which is influenced by dopamine-related genes: the DA transporter (DAT) (SLC6A3), the DA D2 receptor (DRD2), and the DA D4 receptor (DRD4) genes. The purpose of this study was to explore the relationship between dopamine-related gene polymorphisms and food consumption in ADHD children receiving varying doses of MPH.

METHODS

In a randomized, within-subject, double-blind design, 58 ADHD children (ages 6-12 years) received placebo, 0.15, 0.3, or 0.6 mg/kg of MPH three times daily over 9 weeks. Observations of percent lunch consumed as a function of dopamine-related genotypes and MPH dose were analyzed using mixed effects regression models.

RESULTS

A significant dose-response reduction in eating was observed across all genotypes (p < 0.001). There was an interaction of DAT SLC6A3 and DRD2 genotypes and dose, because 9/9 DAT children showed a stronger effect of dose when compared with the 9/10 and 10/10 children (p < 0.001) and DRD2 A2/A2 children showed a stronger effect of dose when compared with A1/A1 and A1/A2 children combined (p = 0.007). There was no significant interaction of dose by DRD4 genotype.

CONCLUSIONS

Lunch consumption decreased as a function of MPH dose. DA-related genotypes associated with greater brain DA signaling moderated the influence of drug on consumption. These results provide information relevant to predicting which children are likely to experience the greatest appetite suppression when taking MPH.

Stimulant dosing for children with ADHD: a medical claims analysis

OBJECTIVE

To evaluate stimulant dosing patterns in the community treatment of children with attention-deficit/hyperactivity disorder (ADHD).

METHOD

Claims data from U.S. managed care organizations (2000-2004) were analyzed for patients ages 6 to 12 years treated for ADHD with osmotically released oral system (OROS) methylphenidate (MPH; n = 3,815), immediate-release (IR) MPH (n = 1,960), mixed amphetamine salts extended-release (MAS XR; n = 1,847), or IR MAS (n = 1,937), and who filled prescriptions covering at least 72 of the first 90 days of treatment.

RESULTS

The mean initial and maximum dosages were 23.8 and 33.4 mg/day for OROS MPH, 14.8 and 21.8 mg/day for IR MPH, 12.7 and 17.4 mg/day for MAS XR, and 11.2 and 16.5 mg/day for IR MAS. Dose titration occurred in 51.8% (MAS XR) to 61.6% (IR MPH) of patients. Lower initial dose and three or more visits for the treatment of ADHD during the first 90 days of treatment were associated with dose titration. Maximum dose was significantly related to higher initial dose and titration for all four stimulants. For children treated with OROS MPH or IR MAS, treatment by a psychiatrist was significantly related to higher maximum dose.

CONCLUSIONS

Among children with ADHD who continue stimulants through the first 3 months of treatment, dosing in the community treatment of ADHD tends to be lower than doses used in clinical trials. When titration does occur, it is linked to lower initial dosing, clinical monitoring, higher final stimulant doses, and treatment by a psychiatrist.

Objective versus subjective assessment of methylphenidate response

Subjective improvement-assessment in attention deficit/hyperactivity disorder (ADHD), following a single dose of methylphenidate (MPH) was compared to performance on the Test-of-Variables-of-Attention (TOVA). Self-perception was assessed with the clinical-global-impression-of-change (CGI-C). Participants included 165 ADHD subjects (M:F ratio 67%:33%) aged 5-18 (11.09 +/- 3.43) years. TOVA was administered before and after MPH challenge (0.3 mg/kg). Self-perception CGI-C scores were compared to the TOVA scores. An inverse correlation was found only between CGI-C and the TOVA-Commission-scores (r = -0.326, p < 0.001). We thus conclude that subjective reports are too unreliable to be used in order to assess MPH benefit in ADHD pediatric populations.

Venlafaxine in the treatment of children and adolescents with attention-deficit/hyperactivity disorder

OBJECTIVE

The objectives of this pilot study were to explore the changes in symptom severity, tolerability, and the pharmacodynamics of venlafaxine treatment in youths with attention-deficit/hyperactivity disorder (ADHD).

METHODS

This was a 2-week, open-label, outpatient trial of venlafaxine in children and adolescents, ages 5-17 years, with ADHD. Three dosing strata, 0.5, 1.0, and 2.0 mg/kg per day, were examined. ADHD symptom severity and improvement assessments included the ADHD Rating Scale (ARS-IV) and the Clinical Global Impressions Scale (CGI). During this study, venlafaxine, O-desmethylvenlafaxine (ODV), norepinephrine, and serotonin concentrations were obtained.

RESULTS

Thirty-eight participants (33 males) were treated in this trial. Overall, parent-completed and teacher-completed ARS-IV total scores showed a statistically significant positive change at the end of the study when compared to baseline (p < 0.05). Significant increases in plasma venlafaxine concentrations were observed at day 15 when compared to day 8 (p = 0.04). In addition, plasma norepinephrine and serotonin concentrations were found to be significantly decreased from baseline at end of study (p < 0.05). Four patients ended participation in the study prematurely: lost to follow up (n = 2), withdrawal of consent (n = 1), and worsening of ADHD symptoms after 8 days of treatment (n = 1). There were no discontinuations due to other adverse events.

CONCLUSIONS

Venlafaxine appeared to offer some benefit and appears to be relatively safe for the short-term treatment of ADHD in this open-label trial. The pharmacodynamics of venlafaxine in youths are consistent with serotonergic and neuradrenergic modulation.

A randomized, double-blind, placebo-controlled clinical trial on once-daily atomoxetine in Taiwanese children and adolescents with attention-deficit/hyperactivity disorder

OBJECTIVE

The aim of this study was to assess the efficacy and safety of the once-daily atomoxetine compared with placebo in pediatric patients with attention-deficit/hyperactivity disorder (ADHD) in Taiwan.

METHOD

The study sample included 106 patients aged 6-16 years who met the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria of ADHD randomly assigned to atomoxetine once daily (n = 72) and placebo once daily (n = 34) in a double-blind, 6-week treatment study. The primary efficacy measure was the total score of the ADHD Rating Scale-IV Parents Version: Investigator Administered and Scored. The secondary efficacy measures included the Clinical Global Impressions--ADHD--Severity and Chinese Conner's Parent and Teacher Rating Scale--Revised: Short Form. Data were analyzed on an intent-to-treat basis and a last-observation-carried-forward approach.

RESULTS

The two treatment groups did not differ in demographics and baseline measures. Compared to the placebo group, the atomoxetine group showed significantly greater reductions in ADHD-related symptoms according to the ratings of investigators, parents, and teachers. The treatment effect size of the primary efficacy measure was 0.70 at the end of study. Adverse events reported significantly more frequently with atomoxetine were decreased appetite (36.1%) and nausea (16.6%). No drug-related serious adverse event was observed.

CONCLUSIONS

Once-daily atomoxetine is an effective, well-tolerable, and safe treatment for children and adolescents with ADHD in Taiwan.

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.

Age and medication effects on rhythmic responses in ADHD: Possible oscillatory mechanisms?

Voluntary motor responses in children with attention-deficit hyperactivity disorder (ADHD) may reflect underlying neuronal oscillatory mechanisms. The aims of this study were: (1) to corroborate the presence of rhythmic motor abnormalities on tapping test in children with attention-deficit hyperactivity disorder, shown in previous studies; (2) to delineate the characteristics of ADHD children demonstrating these rhythmic abnormalities; (3) to assess the impact of methylphenidate (Ritalin) on this abnormal motor phenomenon. The study was designed in a double blind manner. Sixty-four ADHD children aged 6-12 years and 60 matched controls underwent a finger tapping test (1-5 Hz). We measured the abnormal rhythmic tapping with and without methylphenidate treatment in a double blind design. Conventional statistical analysis was used to assess the correlation of the presence of motor abnormality with various clinical characteristics (such as degree of hyperactivity/impulsivity). Fifty-six percent of children with ADHD compared to 8% of controls demonstrated abnormal rhythmic responses at a mean frequency of 3.1+/-0.9 Hz. These erroneous voluntary movements were more common in children with a greater degree of hyperactivity, in younger children but not significantly altered by methylphenidate treatment. Surprisingly, abnormal rhythmic responses showed less variability than found for responses for which the tapping was adequately paced, suggesting different motor control processes for normal and abnormal paced tapping. We speculate that rhythmic tapping responses reflect abnormal oscillatory mechanisms involved in ADHD, exacerbated in younger children with ADHD and in those in whom the hyperactivity/impulsivity is more pronounced.

Dopamine transporter in attention-deficit hyperactivity disorder normalizes after cessation of methylphenidate

Attention-deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder of childhood, which is frequently treated with methylphenidate. The short-term response to treatment with methylphenidate is a substantial decrease in dopamine transporter density, with improvement in neuropsychological tests. In this study, single-photon emission computed tomography was used to investigate possible long-term alterations in the cerebral dopamine system after cessation of treatment with methylphenidate in five children with ADHD. Three months after initiation of treatment with methylphenidate, a reduction of the dopamine transporter in the striatal system was observed. Methylphenidate was administered for a period of 9 to 20 months. Follow-up with single-photon emission computed tomography after withdrawal of methylphenidate medication disclosed an increase of dopamine transporter activity comparable with pretreatment values. The observed upregulation of dopamine transporter activity might support the assumption that methylphenidate does not lead to permanent damage of the nigrostriatal dopaminergic pathways.

Plasma level-dependent effects of methylphenidate on task-related functional magnetic resonance imaging signal changes

RATIONALE

Methylphenidate (MPH) is a dopamine and noradrenaline enhancing drug used to treat attentional deficits. Understanding of its cognition-enhancing effects and the neurobiological mechanisms involved, especially in elderly people, is currently incomplete.

OBJECTIVES

The aim of this study was to investigate the relationship between MPH plasma levels and brain activation during visuospatial attention and movement preparation.

METHODS

Twelve healthy elderly volunteers were scanned twice using functional magnetic resonance imaging (fMRI) after oral administration of MPH 20 mg or placebo in a within-subject design. The cognitive paradigm was a four-choice reaction time task presented at two levels of difficulty (with and without spatial cue). Plasma MPH levels were measured at six time points between 30 and 205 min after dosing. FMRI data were analysed using a linear model to estimate physiological response to the task and nonparametric permutation tests for inference.

RESULTS

Lateral premotor and medial posterior parietal cortical activation was increased by MPH, on average, over both levels of task difficulty. There was considerable intersubject variability in the pharmacokinetics of MPH. Greater area under the plasma concentration-time curve was positively correlated with strength of activation in motor and premotor cortex, temporoparietal cortex and caudate nucleus during the difficult version of the task.

CONCLUSION

This is the first pharmacokinetic/pharmacodynamic study to find an association between plasma levels of MPH and its modulatory effects on brain activation measured using fMRI. The results suggest that catecholaminergic mechanisms may be important in brain adaptivity to task difficulty and in task-specific recruitment of spatial attention systems.

An intermittent, controlled-rate, slow progressive degeneration model of Parkinson's disease: antiparkinson effects of Sinemet and protective effects of methylphenidate

The causes of nigrostriatal neuron degeneration in Parkinson's disease (PD) are not known, but it has been suggested that exogenous or endogenous factors or neurotoxins may play a role. The degree of vulnerability to neurotoxins or other potential mediators of nigral dopamine cell death is thought to be important in understanding Parkinson's disease. In most animal models, the rate of terminal degeneration and corresponding functional impairment is too rapid to investigate effectively either cell vulnerability or the potential benefits of some neuroprotective treatments. In the present study, a new model of Parkinson's disease is described that might help in addressing the issue of nigral cell vulnerability and to evaluate interventions with clinical potential. 6-Hydroxydopamine (6-OHDA) was infused in escalating, intrastriatal doses over several weeks. Control animals received multiple infusions of vehicle at the same volume. Behavioral testing was carried out between each infusion, including forelimb-use and somatosensory function. A symptomatic threshold was established for each animal, indicating the amount of neurotoxin required to induce a stable deficit. Oral administration of L-DOPA (Sinemet) ameliorated limb-use asymmetries acutely. An immunocytochemical assay for tyrosine hydroxylase, a dopamine cell marker, revealed a partial loss of immunoreactive cells in the substantia nigra. Animals that were co-administered methylphenidate (MPH), a dopamine transport inhibitor, along with the 6-OHDA were spared from the behavioral and neurochemical effects of 6-OHDA, despite receiving more than twice as much neurotoxin as controls. These data suggest that establishing a symptomatic threshold preclinically may help researchers evaluate potential treatments and model individual and group resistance to nigrostriatal insults.

Use and persistence of pharmacotherapy for elementary school students with attention-deficit/hyperactivity disorder

OBJECTIVE

The aim of this study was to describe rates of attention-deficit/hyperactivity disorder (ADHD) medication treatment and relevant school services use during a 2-year period, and to examine independent predictors of these interventions.

METHOD

Parent and child interviews (n = 266) and follow-up 12-month telephone surveys (n = 220) were conducted among a high-risk sample, selected from a districtwide, stratified, random sample of elementary-school students screened for ADHD risk. Medication treatment status and school services use were assessed from multiple sources, and their predictors were identified by logistic regression modeling, adjusting for sociodemographic and parental characteristics, as well as clinical-need variables.

RESULTS

Approximately one third (35%) of the children received ADHD medications during a 2-year period, and of those treated at Time 2, approximately one third (36%) were no longer on medications at Time 3. Boys were more than twice as likely to receive ADHD medication as girls. Approximately one quarter (28%) of the children accessed school services and continued their use over 2 years. African-American youths were more likely to receive school services than were Caucasian children.

CONCLUSIONS

In this elementary school-district high-risk sample, care for ADHD was remarkable for underuse and attrition of medication treatment, as well as poor linkage to relevant school services. Interventions to improve ADHD care should include supports to access and sustain medication treatment, as well as link with school services, especially for girls.