A review of the pharmacotherapy of adults with attention-deficit/hyperactivity disorder

Cognition as a therapeutic target in late-life depression: potential for nicotinic therapeutics

Depression is associated with impairments to cognition and brain function at any age, but such impairments in the elderly are particularly problematic because of the additional burden of normal cognitive aging and in some cases, structural brain pathology. Individuals with late-life depression exhibit impairments in cognition and brain structural integrity, alongside mood dysfunction. Antidepressant treatment improves symptoms in some but not all patients, and those who benefit may not return to the cognitive and functional level of nondepressed elderly. Thus, for comprehensive treatment of late-life depression, it may be necessary to address both the affective and cognitive deficits. In this review, we propose a model for the treatment of late-life depression in which nicotinic stimulation is used to improve cognitive performance and improve the efficacy of an antidepressant treatment of the syndrome of late-life depression. The cholinergic system is well-established as important to cognition. Although muscarinic stimulation may exacerbate depressive symptoms, nicotinic stimulation may improve cognition and neural functioning without a detriment to mood. While some studies of nicotinic subtype specific receptor agonists have shown promise in improving cognitive performance, less is known regarding how nicotinic receptor stimulation affects cognition in depressed elderly patients. Late-life depression thus represents a new therapeutic target for the development of nicotinic agonist drugs. Parallel treatment of cognitive dysfunction along with medical and psychological approaches to treating mood dysfunction may be necessary to ensure full resolution of depressive illness in aging.

Treating nicotine dependence by targeting attention-deficit/ hyperactivity disorder (ADHD) with OROS methylphenidate: the role of baseline ADHD severity and treatment response

OBJECTIVE

To determine whether treatment of attention-deficit/hyperactivity disorder (ADHD) with osmotic-release oral system (OROS) methylphenidate promotes abstinence from smoking among smokers with ADHD who have greater severity of ADHD symptoms at baseline or greater improvement in ADHD during treatment.

METHOD

This is a secondary analysis of data from a randomized, double-blind, 11-week trial conducted between December 2005 and January 2008 at 6 clinical sites; the original trial was sponsored by the National Drug Abuse Clinical Trials Network. Adult cigarette smokers (aged 18-55 years) who met DSM-IV criteria for ADHD were randomly assigned to OROS methylphenidate (72 mg/d) (n = 127) or matching placebo (n = 128). All participants received nicotine patches (21 mg/d) and weekly individual smoking cessation counseling. Logistic regression was used to model prolonged abstinence from smoking (ascertained by self-report and breath carbon monoxide testing) as a function of treatment, baseline ADHD Rating Scale-IV (ADHD-RS) score, change in ADHD-RS score during treatment, and their interactions.

RESULTS

Treatment interacted with both ADHD-RS score at baseline (P = .01) and change in ADHD-RS score during treatment (P = .008). Among patients with higher ADHD-RS scores (> 36) at baseline and the most improvement in ADHD during treatment (ADHD-RS change score ≥ 24), 70.0% of those who took OROS methylphenidate achieved abstinence from smoking compared to 36.8% of those who took placebo (P = .02). In contrast, among patients with the lowest ADHD-RS baseline scores (≤ 30), 30.3% of those who took OROS methylphenidate achieved abstinence from smoking compared to 60.7% of those who took placebo (P = .02).

CONCLUSIONS

OROS methylphenidate, in combination with nicotine patch, may be an effective treatment for nicotine dependence among smokers with more severe ADHD and more robust response of ADHD symptoms to medication. OROS methylphenidate may be counterproductive among smokers with lower severity of ADHD.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00253747.

Psychoeducation for adults with attention deficit hyperactivity disorder vs. cognitive behavioral group therapy: a randomized controlled pilot study

The aim of the present study was to assess the efficacy of psychoeducation as compared with cognitive behavioral group therapy in adults with attention deficit hyperactivity disorder (ADHD) who still had significant symptoms and were in pharmacological treatment. This is the first study on psychoeducation in adults with ADHD. Thirty-two individuals were randomized to two treatment conditions: 15 were in the psychoeducation group and 11 were in the cognitive behavioral group therapy. A total of 30 completed treatment, and 26 completed the follow-up assessments. The results indicated that both treatments were associated with statistically significant improvements on inattention, hyperactivity, impulsivity, and self-esteem. The patients in both groups showed a decrease in anxiety symptoms and obtained significantly lower scores in depression. Measures on functional impairment showed statistically significant differences on improved quality of life and on lower global severity as perceived in self-report and assessed by clinician report. Psychoeducation demonstrated to be an effective treatment in reducing ADHD core symptoms.

Placebo effects in children: a review

Of more than 155,000 PubMed citations found with the search term "placebo," only ~9,000 (5.8%) included the terms "children" or "adolescents." When all these papers were screened, only ~2,000 of them investigated the placebo effect per se, and of those, only ~50 (2.5%) discussed the placebo effect in children and adolescents. In this narrative review, we explore four aspects of the placebo response in children and adolescents: (i) the legal and ethical limitations and restrictions for the inclusion of children in clinical trials as well as in experimental (placebo) research that may explain the poor knowledge base; (ii) the question of whether or not the placebo effect is larger in children and adolescents as compared with adults; (iii) whether the mechanisms underlying the placebo effect are similar between children and adults; and (iv) whether mediators and moderators of the placebo effect are comparable between children and adults. We finally discuss some of the consequences from the current placebo research in adults that may affect both experimental and clinical research in children and adolescents.

The relationship between attention deficit hyperactivity disorder and premature infants in Taiwanese: a case control study

BACKGROUND

Preterm survivors from the neonatal intensive care unit (NICU) are considered to be at risk for some neurobehavioral disorders such as attention-deficit/hyperactivity disorder (ADHD). The current study aimed to explore the relationship between ADHD and premature infants in Taiwan.

METHODS

A total of 195 children (157 males and 38 females) diagnosed with ADHD based on DSM-IV and aged between 6 to 12 years and a control group of 212 (164 males, 48 females) age- and sex-matched healthy children were enrolled. The ADHD-Rating scale and CGI severity were performed by child psychiatrists. Demographic data of the children, including birth history, perinatal neurological and respiratory problems were collected to facilitate the investigation of whether a correlation exists between ADHD and prematurity.

RESULTS

The ADHD group had a significantly higher rate of prematurity and significantly higher rate of low birth body weight (defined as <2500 g) than the control group (both P=0.003). Pearson correlation showed a significantly negative correlation between gestational age and ADHD-RS score, inattentive score, hyperactivity and CGI-S score (P=0.004, 0.013, 0.015 and 0.002, respectively). However, only a CGI-S score (P=0.018) showed a significantly correlation between low birth weight and ADHD.

CONCLUSIONS

Premature infants have significantly more severe symptoms of ADHD at school age and they were highly correlated. Further study is necessary to determine the main effect and pathogenesis of moderate as well as extreme preterm birth on the development of ADHD.

Distinguishing comorbidity and successful management of adult ADHD

OBJECTIVE

Given high rates of comorbidity, lack of awareness and global acceptance, and varying guidelines for its management, adult ADHD may be an especially difficult condition to diagnose and treat. The objective of this review was to explore and characterize similarities and differences among comorbidities associated with adult ADHD.

METHOD

A review of the literature over the past 10 years was performed using Ovid.

RESULTS

A myriad of comorbid conditions such as impulse-control/personality, anxiety, mood, substance use, learning, and sleep disorders overlap with adult ADHD. Furthermore, a number of such conditions have symptoms that can mimic those of ADHD, including hyperactivity, impulsivity, inattention, and disruption of circadian rhythms, adding to the complexity of recognition and diagnosis of ADHD in adults. Extensive research shows that adults with ADHD appear to benefit from treatment with stimulant medications in similar ways as children, including significant improvements on driving performance. However, fear surrounding the abuse of stimulants is an important issue. Nevertheless, evidence suggests that children with ADHD who are treated with stimulant medication are less likely to develop a substance use disorder in adolescence and adulthood.

CONCLUSION

There are a wide range of comorbidities with adult ADHD with many having overlapping symptoms. The benefits observed with ADHD treatment, however, emphasize the importance of recognition and treatment of adult ADHD.

An update on the pharmacotherapy of attention-deficit/hyperactivity disorder in adults

Adults with attention-deficit/hyperactivity disorder (ADHD) are more frequently presenting for diagnosis and treatment. Medication is considered to be appropriate among available treatments for ADHD; however, the evidence supporting the use of pharmacotherapeutics for adults with ADHD remains less established. In this article, the effectiveness and dosing parameters of the various agents investigated for adult ADHD are reviewed. In adults with ADHD, short-term improvements in symptomatology have been documented through the use of stimulants and antidepressants. Studies suggest that methylphenidate and amphetamine maintained an immediate onset of action, whereas the ADHD response to the nonstimulants appeared to be delayed. At a group level, there appears to be some, albeit not entirely consistent, dose-dependent responses to amphetamine and methylphenidate. Generally speaking, variability in diagnostic criteria, dosing parameters and response rates between the various studies was considerable, and most studies were of a relatively short duration. The aggregate literature shows that the stimulants and catecholaminergic nonstimulants investigated had a clinically significant beneficial effect on treating ADHD in adults.

Cognitive behaviour therapy in medication-treated adults with ADHD and persistent symptoms: a randomized controlled trial

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) in adulthood is not fully treated by psychopharmacological treatment alone. The main aim of the current study was to evaluate a newly developed cognitive behaviour therapy (CBT) based group programme, the Reasoning and Rehabilitation for ADHD Youths and Adults (R&R2ADHD), using a randomized controlled trial.

METHODS

54 adults with ADHD already receiving psychopharmacological treatment were randomly allocated to an experimental (CBT/MED) treatment condition (n = 27) and a 'treatment as usual' (TAU/MED) control condition (n = 27) that did not receive the CBT intervention. The outcome measures were obtained before treatment (baseline), after treatment and at three month follow-up and included ADHD symptoms and impairments rated by independent assessors, self-reported current ADHD symptoms, and comorbid problems.

RESULTS

The findings suggested medium to large treatment effects for ADHD symptoms, which increased further at three month follow-up. Additionally, comorbid problems also improved at follow-up with large effect sizes.

CONCLUSIONS

The findings give support for the effectiveness of R&R2ADHD in reducing ADHD symptoms and comorbid problems, an improving functions associated with impairment. The implications are that the benefits of R&R2ADHD are multifaceted and that combined psychopharmacological and CBT based treatments may add to and improve pharmacological interventions.

TRIAL REGISTRATION

ACTRN12611000533998 (http://www.ANZCTR.org.au/ACTRN12611000533998.aspx).

Scales for the identification of adults with attention deficit hyperactivity disorder (ADHD): a systematic review

Attention deficit hyperactivity disorder (ADHD) is prevalent in the adult population. The associated co-morbidities and impairments can be relieved with treatment. Therefore, several rating scales have been developed to identify adults with ADHD who may benefit from treatment. No systematic review has yet sought to evaluate these scales in more detail. The present systematic review was undertaken to describe the properties, including psychometric statistics, of the currently available adult ADHD rating scales and their scoring methods, along with the procedure for development. Descriptive synthesis of the data is presented and study quality has been assessed by an objective quality assessment tool. The properties of each scale are discussed to make judgements about their validity and usefulness. The literature search retrieved 35 validation studies of adult ADHD rating scales and 14 separate scales were identified. The majority of studies were of poor quality and reported insufficient detail. Of the 14 scales, the Conners' Adult ADHD Rating scale and the Wender Utah Rating Scale (short version) had more robust psychometric statistics and content validity. More research into these scales, with good quality studies, is needed to confirm the findings of this review. Future studies of ADHD rating scales should be reported in more detail so that further reviews have more support for their findings.

Role of zinc in the pathogenesis of attention-deficit hyperactivity disorder: implications for research and treatment

The dopamine transporter is regulated by zinc (Zn2+), which directly interacts with the transporter protein as a potent non-competitive blocker of substrate translocation (dopamine transport inward and outward). The fact that dysfunction of the dopamine transporter is involved in the pathogenesis of attention-deficit hyperactivity disorder (ADHD) is interesting in the context of studies that suggest the involvement of zinc deficiency in patients with ADHD. In this article, we present a hypothesis exploring the causative mechanism of zinc deficiency in ADHD and why zinc might be beneficial as a supplementary medication and/or adjunct to psychostimulants (methylphenidate, amfetamine) in zinc-deficient ADHD patients. The hypothesis is based on published in vitro observations that the human dopamine transporter contains a high-affinity zinc binding site (His-193, His-375, Glu-396) on its extracellular face that modulates transporter function, and in vivo studies suggesting that response to stimulants is reduced in zinc-deficient ADHD patients. It seems likely that zinc supplementation in zinc-deficient ADHD patients improves the binding status of insufficiently occupied zinc binding sites on the dopamine transporter. We propose to test our hypothesis by recruiting zinc-deficient ADHD patients who will undergo positron emission tomography with the 11C-raclopride displacement method to investigate whether zinc increases extracellular dopamine levels.

Efficacy of meta-cognitive therapy for adult ADHD

OBJECTIVE

The authors investigated the efficacy of a 12-week manualized meta-cognitive therapy group intervention designed to enhance time management, organization, and planning in adults with attention deficit hyperactivity disorder (ADHD).

METHOD

Eighty-eight clinically referred adults who met DSM-IV criteria for ADHD according to clinical and structured diagnostic interviews and standardized questionnaires were stratified by ADHD medication use and otherwise randomly assigned to receive meta-cognitive therapy or supportive psychotherapy in a group modality. Meta-cognitive therapy uses cognitive-behavioral principles and methods to impart skills and strategies in time management, organization, and planning and to target depressogenic and anxiogenic cognitions that undermine effective self-management. The supportive therapy condition controlled for nonspecific aspects of treatment by providing support while avoiding discussion of cognitive-behavioral strategies. Therapeutic response was assessed by an independent (blind) evaluator via structured interview before and after treatment as well as by self-report and collateral informant behavioral ratings.

RESULTS

General linear models comparing change from baseline between treatments revealed statistically significant effects for self-report, collateral report, and independent evaluator ratings of DSM-IV inattention symptoms. In dichotomous indices of therapeutic response, a significantly greater proportion of members of the meta-cognitive therapy group demonstrated improvement compared with members of the supportive therapy group. Logistic regression examining group differences in operationally defined response (controlling for baseline ADHD severity) revealed a robust effect of treatment group (odds ratio=5.41; 95% CI=1.77-16.55).

CONCLUSIONS

Meta-cognitive therapy yielded significantly greater improvements in dimensional and categorical estimates of severity of ADHD symptoms compared with supportive therapy. These findings support the efficacy of meta-cognitive therapy as a viable psychosocial intervention.

Life impairments in adults with medication-treated ADHD

OBJECTIVE

In developing psychosocial approaches to augment outcomes for medication-treated adults with ADHD, it is important to understand what types of life-impairments are most affected by continued ADHD symptoms that occur despite medication treatment. This may assist in delineating targets for interventions, as well as assessments of functional outcomes that are sensitive to change in this population.

METHOD

The sample consists of 105 adults with ADHD presenting for entry into clinical trials of CBT for residual ADHD. Life impairments are rated by a clinician using the LIFE-RIFT, which has subscales for work impairment, interpersonal impairment, life-satisfaction, and recreation, ADHD symptoms using the ADHD Rating Scale, overall ADHD severity using the clinical global impression, and associated distress using the Hamilton Depression and Anxiety Rating Scales.

RESULTS

The most problematic impairments are in the domain of work, followed by interpersonal. Generally, the subscales of the LIFE-RIFT are associated, at the bivariate level, with all 4 symptom indices. Work and interpersonal impairments are uniquely associated with overall severity of ADHD symptoms using both the CGI and the ADHD Rating Scale. However interpersonal and life-satisfaction impairments are uniquely associated with depression, and life-satisfaction is uniquely associated with anxiety.

CONCLUSION

In medication-treated adults with ADHD, work and interpersonal impairments appear to be the most problematic areas of life-impairment, which are uniquely associated with ADHD severity. Life-satisfaction appears to be uniquely associated with distress as defined by anxiety and depression symptoms, with interpersonal impairments also playing a role. Psychosocial treatments for medication treated adults should target work and interpersonal domains and should include skills for managing associated distress.

Extended access to amphetamine self-administration increases impulsive choice in a delay discounting task in rats

BACKGROUND

d-Amphetamine (AMPH) is a widely prescribed attention deficit hyperactivity disorder medication, but little is known about its effects on impulsive choice with escalated use.

OBJECTIVE

The current study examined the effects of short and long access to AMPH self-administration on impulsive choice in a delay discounting task in which rats chose between a small immediate reward (one sucrose pellet immediately) and a larger delayed reward (three sucrose pellets after an adjusting delay).

METHODS

Following choice stability in delay discounting, all rats received 15 1-h sessions of AMPH self-administration (0.1 or 0.03 mg/kg/infusion); self-administration sessions began 45 min after each delay discounting session. Rats were then either maintained on the short access (ShA) self-administration session or were switched to a long access (LgA) 6-h session for 21 days, followed by a 7-day withdrawal phase in which only the delay discounting task continued.

RESULTS

LgA rats in the 0.03 mg/kg/infusion dose group escalated in total number of infusions across sessions, although rats in the 0.1 mg/kg/infusion dose group did not. LgA groups at both unit doses showed decreased mean adjusted delays across sessions compared to the ShA groups, indicating that long access to AMPH increases impulsive choice. During the AMPH withdrawal phase, LgA groups returned back to baseline mean adjusted delays, indicating that the effect on impulsive choice was reversible.

CONCLUSION

These results show that extended AMPH self-administration produces a transient loss of inhibitory control, which may play a role in the escalating pattern of drug intake that characterizes the addiction process.

Evaluation of group cognitive behavioral therapy for adults with ADHD

OBJECTIVE

A brief cognitive behavioral therapy (CBT) group intervention was designed to treat comorbid anxiety, depression, and low self-esteem and self-efficacy in adults with ADHD. It was hypothesised that participants would gain knowledge about ADHD, experience a reduction in comorbid symptoms, and benefit from the supportive aspect of group treatment.

METHOD

Participants in the study formed a CBT treatment group that attended six workshops and a waiting list control group. The intervention was evaluated with measures assessing knowledge about ADHD, psychological symptoms, and support received. The groups were compared using repeated measures ANOVAs.

RESULTS

The CBT group had significantly greater improvement on measures of knowledge about ADHD, self-efficacy, and self-esteem than the control group. Participants' evaluations of the sessions suggested that sharing personal experiences with other adults with ADHD was an important aspect of the intervention.

CONCLUSION

Brief CBT group treatments may be an acceptable and cost-effective intervention for adults with ADHD.

Management of attention-deficit hyperactivity disorder in adults: focus on methylphenidate hydrochloride

Attention-deficit hyperactivity disorder (ADHD) is one of the most common psychiatric disorders in young adults and causes significant psychosocial impairment and economic burden to society. Because of the paucity of long-term evidence and lack of national guidelines for diagnosis and management of adult ADHD, most of the data are based on experience derived from management of childhood ADHD. This article reviews the current evidence for the diagnosis and management of adult ADHD with special emphasis on the role of methylphenidate hydrochloride preparations in its treatment. Methylphenidate hydrochloride, a stimulant that acts through the dopaminergic and adrenergic pathways, has shown more than 75% efficacy in controlling the symptoms of adult ADHD. Although concern for diversion of the drug exists, recent data have shown benefits in preventing substance use disorders in patients with adult ADHD.

Attention-deficit/hyperactivity disorder in adults: evidence-based recommendations for management

Attention-deficit/hyperactivity disorder (ADHD) is associated with impairments in educational, occupational, neuropsychological, and social functioning in adults. Successful diagnosis and treatment of the disorder in adults can be a challenge because recent and integrative clinical guidelines are lacking and diagnostic criteria are based on making a retrospective diagnosis of childhood-onset ADHD. To develop evidence-based recommendations for the treatment of ADHD in adults, the scientific literature was reviewed, including primary clinical studies, meta-analyses, and available clinical guidelines. Studies show that stimulant therapy is highly effective and safe in the management of ADHD in adults, with similar response rates to those reported in children at doses that are equivalent on a mg/kg basis. Long-acting stimulants, such as OROS methylphenidate (OROS MPH, Concerta), dexmethylphenidate (d-MPH, Focalin), and mixed amphetamine salts extended release (MAS XR, Adderall XR), have durations of action of up to 10 to 12 hours, which permit once-daily dosing. For adults with ADHD who do not respond to stimulant therapy or who have a comorbid condition in which a stimulant is contraindicated, the nonstimulant atomoxetine (Strattera) may be an appropriate alternative. For many adults, cognitive-behavioral therapy in addition to pharmacotherapy may improve treatment response. Attention-deficit/hyperactivity disorder medications may increase blood pressure and heart rate in adults, so patients should be monitored.

Comorbidity of adult attention-deficit hyperactivity disorder and bipolar disorder: prevalence and clinical correlates

The aim of this study was to determine the frequency of adult attention deficit hyperactivity disorder (ADHD) comorbidity with lifetime bipolar disorder, and the influence of this comorbidity on various demographic and clinical variables in patients. Patients (n=159) with a previous diagnosis of bipolar disorder (79 female, 80 male) were included in this study. All patients were interviewed for the presence of current adult and childhood ADHD diagnosis and other axis I psychiatric disorder comorbidities using the structured clinical interview for DSM-IV (SCID) and the Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime Version (K-SADS-PL). The subjects also completed a Wender Utah rating scale (WURS-25) and a Current Symptoms Scale for ADHD symptoms. In particular, patients' clinical characteristics, the age of onset of bipolar disorder, and the number of episodes were noted. Twenty-six of the 159 bipolar patients (16.3%) were diagnosed with adult ADHD, while another subgroup of patients (n=17, 10.7%) received a diagnosis of childhood ADHD but did not fulfill criteria for adult ADHD. Both of these two subgroups (patients with adult ADHD, and patients with only childhood ADHD) had an earlier age of onset of the disease and a higher number of previous total affective or depressive episodes than those without any lifetime ADHD comorbidity. However only bipolar patients with adult ADHD comorbidity had higher lifetime comorbidity rates for axis I psychiatric disorders, such as panic disorder and alcohol abuse/dependence, compared to patients without lifetime ADHD. Bipolar patients with comorbid adult ADHD did not differ from bipolar patients with comorbid childhood ADHD in terms of any demographic or clinical variables except for adult ADHD scale scores. In conclusion, ADHD is a common comorbidity in bipolar patients, and it adversely affects the course of the disease and disrupts the social adjustment of the patients. Regular monitoring of ADHD will help to prevent problems and complications that could arise in the course of the disease, particularly in patients with early onset bipolar disorder.

Recent developments in the psychosocial treatment of adult ADHD

Adult attention-deficit/hyperactivity disorder (ADHD) is an increasingly recognized Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV psychiatric disorder associated with significant functional impairment in multiple domains. Although stimulant and other pharmacotherapy regimens have the most empirical support as treatments for ADHD in adults, many adults with the disorder continue to experience significant residual symptoms. In the present manuscript, we review the published studies examining group and individual psychosocial treatments for adult ADHD. We include a discussion of coaching interventions and how they differ from cognitive-behavioral therapy. We conclude that the available data support the use of structured, skills-based psychosocial interventions as a viable treatment for adults with residual symptoms of ADHD. Common elements across the various treatment packages include psychoeducation, training in concrete skills (e.g., organization and planning strategies) and emphasis on outside practice and maintenance of these strategies in daily life. These treatments, however, require further study for replication, extension and refinement. Finally, we suggest future directions for the application of psychosocial treatments to the problems of adults with ADHD.

Treating adult ADHD with stimulants

Treatment of attention-deficit/hyperactivity disorder (ADHD) may positively impact the neurobiology of adult patients with ADHD. Treatment may also minimize impairment from core symptoms and may alter the course of co-morbid disorders such as depression and substance use disorder. However, much of the information on stimulant use in adult ADHD comes from studies conducted in children, and it remains unclear whether there is a difference between children and adults when it comes to the side effects and tolerability of ADHD treatments. It is known that clinical presentation differs between adults and children, with adults demonstrating a higher percentage of mood disorders. Current treatments for adult ADHD include psychosocial therapies and pharmacologic therapies, the latter of which include the stimulants d-methylphenidate extended release (XR), OROS methylphenidate, lisdexamfetamine, and mixed amphetamine salts XR; and the nonstimulant atomoxetine, a selective norepinephrine reuptake inhibitor. There is need for additional study of treatment strategies for adult ADHD. Although all classes of ADHD medications are approved in adults, there are fewer approved formulations for adults than for children. Efficacy in adults is more subjective than in children, which may affect how efficacy rates for adult treatments are calculated. Adults also present a greater diversion risk than children. In addition, there are several new and emerging medication treatments worth considering.

This Expert Roundtable Supplement represents part 2 of a 3-part supplement series on adult ADHD led by Lenard A. Adler, MD. In this activity, Thomas J. Spencer, MD, discusses the neurobiology and genetics of adult ADHD; Mark A. Stein, PhD, discusses stimulant therapy; and Jeffrey H. Newcorn, MD, reviews nonstimulants and psychosocial treatments.

A bibliometric study of international scientific productivity in attention-deficit hyperactivity disorder covering the period 1980-2005

OBJECTIVE

We have carried out a bibliometric analysis of scientific publications related to attention-deficit hyperactivity disorder (ADHD) and its pharmacological treatment over the period 1980-2005.

METHOD

We selected (in EMBASE and MEDLINE databases) documents that contained in their title the descriptors attention deficit hyperactivity disorder, attention deficit disorder, ADHD and ADD. As bibliometric indicators of production and dispersion we applied Price's Law and Bradford's Law, respectively. We also calculated the national participation index (PI) and correlated it with overall PI in biomedical and health sciences, with PI in the discipline of Psychiatry and with the social-health indicators (per capita Gross Domestic Product, number of physicians and total per capita expenditure on health).

RESULTS

We obtained 5,269 original documents (2,325 corresponded to pharmacological therapy). Our results indicate fulfilment of Price's Law, since scientific production on ADHD undergoes exponential growth (correlation coefficient r = 0.9859, vs. r = 0.9011 after linear adjustment). The most widely studied drugs are methylphenidate (1,251 documents). Division into Bradford zones yields a nucleus occupied exclusively by the Journal of the American Academy of Child and Adolescent Psychiatry (500 articles). A total of 866 different journals were employed. Twelve of the first 20 used journals have an Impact Factor > 2. The principal producer country is the United States (PI = 44.2). Only four countries, of the 20 major producers in health sciences, surpass their own PI in the field of Psychiatry (Brazil, China, Spain and the United States). The correlation between PI and total number of physicians for each country situates Canada, Australia, the United States and Israel in the top positions.

CONCLUSION

Productivity on ADHD has undergone exponential growth in the period 1980-2005, without evidence a saturation point.

Pharmacotherapy of adult attention deficit/hyperactivity disorder: review of evidence-based practices and future directions

BACKGROUND

Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed psychiatric disorder in children and adolescents with well-known clinical consequences and functional outcomes that affect individuals throughout their lifespan. The diagnosis of adult ADHD is often a clinical diagnosis made on the basis of behavioral symptoms that begin early in life, and persist over time across different settings.

OBJECTIVE

Although pharmacotherapy is a first-line treatment option for ADHD across all age groups, there is a relative paucity of well-designed and well-controlled studies evaluating the treatment outcomes in adult ADHD. In this review, evidence-based pharmacotherapy of adult ADHD and directions of future research are critically examined.

METHODS

A literature search from 1980 to 2007, restricting papers to English, using PUBMED and PsychInfo was performed. Studies were examined based on empirically derived criteria.

RESULTS

The reviewed body of evidence strongly supports the use of pharmacotherapy as a first-line therapeutic option for the treatment of adults with ADHD.

A randomized controlled trial of a novel mixed monoamine reuptake inhibitor in adults with ADHD

BACKGROUND

NS2359 is a potent reuptake blocker of noradrenalin, dopamine, and serotonin. The aim of the study was to investigate the efficacy, safety and cognitive function of NS2359 in adults with a DSM IV diagnosis of ADHD.

METHODS

The study was a multi-centre, double-blind, randomized placebo-controlled, parallel group design in outpatient adults (18-55 years) testing 0.5 mg NS2359 vs. placebo for 8 weeks. Multiple assessments including computerized neuropsychological evaluation were performed.

RESULTS

There was no significant difference between NS2359 (n = 63) versus placebo (n = 63) on the primary outcome measure reduction in investigator rated ADHD-RS total score (7.8 versus 6.4; p < 0.45). However, in subjects with the inattentive subtype, there were significantly more responders in the NS2359 group compared to placebo (41% versus 7%; p < 0.01). For all secondary variables (ADHD-RS patient rated; The Conners Adult ADHD Scale; The Brown Adult Scale, and CGI-improvement scale) there were no significant differences between the two groups; however, in the inattentive subgroup, the response to treatment was significantly larger than to placebo. NS2359 improved composite factor scores of attention, episodic- and working memory. No serious adverse events were reported with insomnia, headaches and loss of appetite most commonly reported as side effects.

CONCLUSION

No overall effect of NS2359 was found on overall symptoms of ADHD. There was also a modest signal of improvement in the inattentive adults with ADHD and cognition warranting further exploration using differing doses.

Differential pharmacokinetics and pharmacodynamics of methylphenidate enantiomers: does chirality matter?

d,l-threo-methylphenidate (MPH) is an effective first-line treatment for the symptoms associated with attention-deficit/hyperactivity disorder. threo-methylphenidate inhibits the dopamine transporter and the norepinephrine transporter, resulting in elevations of these monoamines after impulse release. Although MPH has long been administered as a racemic mixture of the 2 enantiomers, d-MPH and l-MPH, converging lines of evidence drawn from investigations using in vitro systems, animal models, and humans indicate that it is predominantly, if not exclusively, d-MPH that mediates the pharmacological/therapeutic actions of MPH. In both rodent and primate animal models, the binding of radiolabeled d-MPH to dopamine transporter was found to be selective, saturable, and reversible, whereas binding of l-MPH was diffuse and nonspecific. The behavioral effects of the enantiomers of MPH have been tested in several animal models, and results indicate these observed behavioral changes are likewise mediated by d-MPH, whereas l-MPH has little or no effect.The contribution of the l-isomer to the overall pharmacological profile of the racemate remains unclear, owing to several studies suggesting that l-MPH may not be merely an inert isomeric ballast. For example, behavioral studies conducted in rats demonstrate an attenuation of the effect of d-MPH in animals pretreated with l-MPH, suggesting that l-MPH may interfere with the action of the active enantiomer. The importance of MPH chirality to central nervous system MPH receptor targeting has culminated in human imaging studies revealing that d-MPH binds specifically to striatal structures, whereas l-MPH binding is nonspecific. Taken together, data from in vitro, animal, and human studies support the premise that the d-enantiomer of MPH mediates the neurophysiological actions of MPH and therefore likely mediates its clinical efficacy.

Can methylphenidate reduce fall risk in community-living older adults? A double-blind, single-dose cross-over study

OBJECTIVES

To test the hypothesis that methylphenidate modifies markers of fall risk in older adults.

DESIGN

Randomized, double-blind, placebo-controlled, single-dose cross-over study.

SETTING

Outpatient movement disorders clinic.

PARTICIPANTS

Twenty-six community-living older adults without dementia (mean age 73.8) with subjective complaints of "memory problems."

INTERVENTIONS

The study examined the effects of a single dose of 20 mg of methylphenidate (MPH) on cognitive function and gait. Participants were evaluated before and 2 hours after taking MPH or a placebo in sessions 1 to 2 weeks apart.

MEASUREMENTS

The Timed Up and Go and gait variability quantified mobility and fall risk. A computerized neuropsychology battery quantified memory and executive function (EF).

RESULTS

Timed Up and Go times, stride time variability, and measures of EF significantly improved in response to MPH but not in response to the placebo. In contrast, MPH did not significantly affect memory or finger tapping abilities.

CONCLUSION

In older adults, MPH appears to improve certain aspects of EF, mobility, and gait stability. Although additional studies are required to assess clinical utility and efficacy, the present findings suggest that methylphenidate and other drugs that are designed to enhance attention may have a role as a therapeutic option for reducing fall risk in older adults.

Treatment of adult ADHD: is current knowledge useful to clinicians?

Psychostimulant drugs have for decades been considered the cornerstone of ADHD treatment. Non-stimulant drugs have also been reported successful. However, many controlled studies exclude patients with comorbidities typical for patients seen in clinical setting. Many patients are also considered non-responders to medication. Current knowledge might not be directly useful to clinicians. The present article reviews the literature on pharmacological and psychotherapeutic treatment in adult ADHD emphasizing comorbidity and other clinically important factors, as well as ADHD specific outcomes. Thirty-three relevant studies of pharmacotherapy and three studies of psychotherapy were included. Most subjects had little current comorbidity, but some studies included subjects with substance use disorder. Significant effect of treatment on ADHD symptoms was found in most studies using pharmacotherapy and all studies of psychotherapy. Both positive and negative effects on comorbid anxiety and depression measures were reported. Pharmacotherapy did not seem to have effect on substance use disorder. Few pharmacotherapy studies conducted any long-term follow-up; two studies that did, found that most subjects had discontinued medication. A clear-cut dose-respons relationship was not substanciated. In conclusion, clinicians have good support for both pharmacological and psychotherapeutic treatment of ADHD in adults, but should take additional measures to deal with comorbidities as well as treatment adherence.

Neuronal nicotinic receptor agonists for the treatment of attention-deficit/hyperactivity disorder: focus on cognition

Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed neurobehavioral disorder in children and adolescents, and in about half of these patients, significant symptomology continues into adulthood. Although impulsivity and hyperactivity are the most salient features of ADHD, cognitive deficits, particularly impairments in attention and executive function, are an important component, particularly in adolescents and adults, with over 90% of adults seeking treatment for ADHD manifesting cognitive dysfunction. Currently available medications treat the core ADHD symptoms but typically do not adequately address cognitive aspects of ADHD, underscoring the need for new therapeutics. Dopamine and norepinephrine are hypothesized to be particularly important in ADHD, but there is emerging evidence that cholinergic neurotransmission, particularly involving neuronal nicotinic acetylcholine receptors (nAChRs), may play a role in the pathophysiology of ADHD. Nicotine has demonstrated procognitive effects in both humans and experimental animals and has produced signals of efficacy in small proof-of-concept adult ADHD trials. Although adverse effects associated with nicotine preclude its development as a therapeutic, a number of novel nAChR agonists with improved safety/tolerability profiles have been discovered. Of these, ABT-418 and ABT-089 have both demonstrated signals of efficacy in adults with ADHD. Notably, tolerability issues that might be expected of a nAChR agonist, such as nausea and emesis, were not observed at efficacious doses of ABT-089. Further understanding of the effects of novel neuronal nAChR agonists on specific aspects of cognitive functioning in ADHD is required to assess the full potential of this approach.

Gait in attention deficit hyperactivity disorder

BACKGROUND

Cognitive function and the loading of attention presumably play an important role in gait as well as in fall risk, but previous work has not demonstrated this in any cause-and-effect way.

OBJECTIVES

To gain insight into the relationship between gait and cognitive function, we sought: (1) To compare the gait rhythmicity (stride time variability) of children with attention deficit hyperactivity disorder (ADHD) to controls, (2) To test the hypothesis that dual tasking leads to increased stride-to-stride variability in ADHD, and (3) To test whether pharmacological treatment that relieves ADHD symptoms reduces stride-to-stride variability.

PATIENTS AND METHODS

Gait was quantified in children with ADHD and in age-matched healthy controls under single task and dual task conditions on three occasions: off medications (both groups) and, in the ADHD group, after double blinded, randomized administration of methylphenidate (MPH) or placebo.

RESULTS

At baseline, children with ADHD tended to walk with increased stride-to-stride variability compared to the controls during the single task condition (p = 0.09). During dual task walking, stride time variability was significantly reduced in the children with ADHD (p < 0.004), but not in the controls. In the children with ADHD, the placebo did not significantly affect stride-to-stride variability or the dual tasking response. In contrast, stride time variability was significantly reduced on MPH (p < 0.001) such that dual tasking no longer affected variability.

CONCLUSIONS

The present findings demonstrate alterations in the gait of children with ADHD, support a cause and effect link between cognitive function and gait, and suggest that enhancement of attention abilities may, in certain populations, improve gait rhythmicity.

The pathophysiology, medical management and dental implications of adult attention-deficit/hyperactivity disorder

BACKGROUND

Few published reports in the dental literature have focused on adult attention-deficit/hyperactivity disorder (ADHD) and its dental implications.

TYPES OF STUDIES REVIEWED

The authors conducted a MEDLINE search for the period 2000 through 2005 using the terms "adult" and "attention-deficit" to define ADHD's pathology, medical treatment and dental implications.

RESULTS

ADHD is a developmental condition that affects slightly more than 4 percent of the adult U.S. population. Its symptoms include inattention, hyperactivity and impulsivity that can cause personal, social, occupational and leisure-time dysfunction. Medications used to treat the disorder include stimulants, selective noradrenergic uptake inhibitors and tricyclic antidepressants.

CLINICAL IMPLICATIONS

The oral health of people with ADHD may be compromised by inattention and impulsivity that impair home care regimens and can lead to cigarette addiction, which may cause oral cancer and damage the periodontium, and excessive ingestion of caffeinated sugar-laden soft drinks that promote dental caries. To safely care for this patient population, dentists must be familiar with the stimulant and nonstimulant medications used to treat adult ADHD, because these drugs can cause adverse orofacial and systemic reactions and interact adversely with dental therapeutic agents.

Does Methylphenidate Improve Inhibition and Other Cognitive Abilities in Adults with Childhood-Onset ADHD?

We examined the effect of methylphenidate (Mph) on inhibition and several other cognitive abilities in 43 adults with Attention Deficit Hyperactivity Disorder (ADHD) by use of Conners' Continuous Performance Test (CPT) and the Change Task (ChT), an extension of the Stop Signal Test (SST). In a double blind, cross-over, placebo controlled study with Mph, tests were administered during the third week of individually titrated treatment with Mph (maximum dose 1 mg / kg / day) and during the third week of treatment with placebo. We established large medication effects for commission errors, standard error of mean reaction time, and attentiveness on the CPT, as well as moderate medication effects for mean reaction time on the CPT and response re-engagement speed on the ChT. For Stop Signal Reaction Time (SSRT) on the ChT, we also established large effects of Mph, but only in a group of participants who showed slow SSRTs on placebo. Mph indeed ameliorates inhibition, which is the core problem of ADHD, and certain other cognitive abilities in adults with ADHD.

Medication adherence in psychopharmacologically treated adults with ADHD

OBJECTIVE

One of the potential causes of residual symptoms of ADHD in adults can be difficulties with consistent adherence to medications.

METHOD

This formative study examined self-reported medication adherence in adults with ADHD with clinically significant symptoms despite medication treatment.

RESULTS

Mean adherence for the two-week period prior to the assessment point was 86%, with 18% of the sample reporting less than 80% adherence, and 43% less than 90% adherence. Adherence correlated with ADHD symptoms but not anxiety or depression. Those with less than 80% adherence had higher ADHD severity compared to those whose adherence was at least 80%.

CONCLUSION

These data suggest that self-report of adherence to ADHD medications may be a useful and expedient way of assessing adherence, and that assessment and counseling about adherence may be an important part of treatment. Future research using an objective indicator of adherence is needed to follow up on these findings.

Attention Deficit Hyperactivity Disorder Across the Lifespan: The Child, Adolescent, and Adult

Management of a child, adolescent, college student, or adult with ADD/ADHD (ADHD) is reviewed with emphasis on pharmacologic approaches in the adult. Psychological treatment includes psychotherapy, cognitive-behavior therapy, support groups, parent training, biofeedback, meditation, and social skills training. Medications are reviewed that research has revealed can improve the core symptomatology of a child or adolescent with ADHD. These medications include stimulants (psychostimulants), antidepressants, alpha-2 agonists, and a norepinephrine reuptake inhibitor. Psychopharmacology approved and/or used in pediatric patients are also used in adults with ADHD, though most are not officially FDA-approved. It is emphasized that ADHD management should include a multi-modal approach, involving appropriate educational interventions, appropriate psychological management of the patient of any age, and judicious use of medications. Such an approach is recommended to benefit those with ADHD achieve their maximum potential across the human life span.

Clinical assessment and treatment of attention deficit hyperactivity disorder in adults

Attention deficit hyperactivity disorder (ADHD) is a common childhood disorder that frequently persists into adulthood, with significant levels of inattentive, hyperactive and impulsive behavior. Impairments associated with adult ADHD include distress from the symptoms, impaired ability to function in work and academic settings, and problems sustaining stable relationships. The disorder is commonly associated with volatile moods, antisocial behavior, and drug and alcohol misuse. There is an increased risk of developing comorbid anxiety, depression, personality disorders, and drug and alcohol dependence. Despite the proven effectiveness of drugs such as methylphenidate, dexamphetamine and atomoxetine, few cases of ADHD are recognized and treated in the UK. The reasons for this are unclear, since most psychiatrists working with children and adolescents are aware that ADHD commonly persists into adult life and they also see the disorder affecting parents of children with ADHD. Issues of transition from the care of child to adult psychiatry and the need to refer adult relatives of children with ADHD to suitable psychiatric services are a major concern. Furthermore, many cases of adult ADHD go unrecognized or are seen by mental health teams that are not familiar with the subtleties of the adult presentation. As a result, misdiagnosis and treatment for conditions such as atypical depression, mixed affective disorder, cyclothymia, and borderline and unstable emotional personality disorders is not uncommon. There is therefore a requirement for further training in this area. This review will describe the common clinical presentation and provide guidelines for the diagnosis and treatment of ADHD in adults. Any psychiatrically trained physician using standard psychiatric assessment procedures can perform clinical evaluations for adult ADHD. As with other psychiatric disorders in adulthood, ADHD has its own characteristic onset, course and psychopathology. Symptoms of ADHD are trait-like, being stable characteristics from early childhood, and commonly co-occur with affective instability. Stimulants are the mainstay of treatment and are effective in around 70% of cases. Psychotherapeutic interventions also have an important role. These guidelines will assist psychiatrists and other adult mental health workers in identifying and treating individuals with adult ADHD.

Different adaptations in ventral tegmental area dopamine neurons in control and ethanol exposed rats after methylphenidate treatment

BACKGROUND

Methylphenidate (MPH) is a psychostimulant effective in treating attention-deficit/hyperactivity disorder (ADHD). Repeated MPH treatment may increase substance abuse risk because of adaptations in dopaminergic (DA) function associated with sensitization to subsequent stimulant exposure. However, this possibility is based on observations in normal animals and may not apply to animals with attention problems linked to compromised DA function such as prenatal ethanol exposed (PE) animals.

METHODS

The electrical activity of ventral tegmental area (VTA) DA neurons was studied after the cessation of repeated MPH treatment at a threshold dose (1 mg/kg/day for 3 weeks) in PE and control rats.

RESULTS

In control rats, there was a continuous increase in VTA DA neuron excitability post-MPH treatment, characterized by a transient increase in population activity (1 day posttreatment) followed by decreased population activity (30-60 days posttreatment) in most of the animals due to depolarization inactivation. In PE rats, MPH treatment decreased the excessive excitability of VTA DA neurons and resulted in prolonged normalization in the population activity (1-60 days posttreatment). These changes were not mediated by altered sensitivity of somatodendritic DA autoreceptors.

CONCLUSIONS

Repeated MPH treatment produced distinctly different effects on VTA DA neuron activity in control and PE animals. These results suggest that repeated MPH treatment for ADHD may not lead to increased substance abuse risk in special populations such as individuals with fetal alcohol spectrum disorder.

Cognitive-behavioral therapy for ADHD in medication-treated adults with continued symptoms

The purpose of the present study was to examine the potential efficacy, patient acceptability, and feasibility of a novel, cognitive-behavioral therapy (CBT) for adults with attention-deficit hyperactivity disorder (ADHD) who have been stabilized on medications but still show clinically significant symptoms. Thirty-one adults with ADHD and stable psychopharmacology for ADHD were randomized to CBT plus continued psychopharmacology or continued psychopharmacology alone. Assessments included ADHD severity and associated anxiety and depression rated by an independent evaluator (IE) and by self-report. At the outcome assessment, those who were randomized to CBT had lower IE-rated ADHD symptoms (p < .01) and global severity (p < .002), as well as self-reported ADHD symptoms (p < .0001) than those randomized to continued psychopharmacology alone. Those in the CBT group also had lower IE-rated and self-report anxiety (p's < .04), lower IE-rated depression (p < .01), and a trend to have lower self-reported depression (p = .06). CBT continued to show superiority over continued psychopharmacology alone when statistically controlling levels of depression in analyses of core ADHD symptoms. There were significantly more treatment responders among patients who received CBT (56%) compared to those who did not (13%) (p < .02). These data support the hypothesis that CBT for adults with ADHD with residual symptoms is a feasible, acceptable, and potentially efficacious next-step treatment approach, worthy of further testing.

[Pharmacological treatment in adults with attention deficit hyperactivity disorder]

Treatment in adults with attention deficit hyperactivity disorder predominantly relies on pharmacotherapeutic approaches especially with psychostimulants. Empirical studies indicate that their clinical effectiveness may be as high as in children and adolescents, especially in higher dosages. However, due to the high prevalence of comorbidities, e.g. depression, psychopharmacological treatment requires an extended use of other substance groups, especially antidepressants. An optimal treatment response necessitates the choice of an adequate substance depending on the leading clinical symptoms and a procedure of an individual titration of different dosages. This article reviews the current empirical results in the pharmacological treatment of ADHD in adults and provides possible treatment strategies for clinical practice.

Psychosocial treatments for adults with attention-deficit/hyperactivity disorder

This article discussed some ways in which a history of failure experiences can enhance negative affect and cognitive avoidance and further impair attentional and organizational abilities associated with ADHD. Accordingly,psychosocial interventions have two targets: providing training in organizational and attentional skills while addressing patterns that motivate demand-related distress and avoidance of these skills. The authors conceptualized these interventions as creating the conditions where patients best can use existing abilities and the benefits offered by medication treatment. As rep-resented by a small but growing literature, there are encouraging signs that structured skill-building treatments of this kind offer benefit to adults with ADHD. Further research on these strategies in the context of well-controlled trials is an essential step for helping reduce disability and distress among this cohort of patients.

Amphetamine-induced chorea in attention deficit-hyperactivity disorder

Attention deficit-hyperactivity disorder (ADHD) is treated frequently with stimulants in both children and adults. While tics are occasional complications of stimulant therapy, chorea is reported rarely. We describe an adult ADHD patient who developed chorea upon dose escalation of mixed amphetamine salts, which resolved on discontinuation of the drug.

Meta-analysis of the efficacy of methylphenidate for treating adult attention-deficit/hyperactivity disorder

This article reviews the efficacy of methylphenidate (MPH) for adult attention-deficit/hyperactivity disorder (ADHD). A literature search identified double-blind placebo-controlled MPH treatment studies of ADHD adults. Meta-analysis estimated the pooled effect size for MPH treatment and tested for publication bias. Meta-analysis regression assessed the influence of study design features on medication effects. Six trials met criteria and were included in this meta-analysis. These studies included a total of 140 MPH-treated ADHD adults and 113 placebo-treated ADHD adults. The mean effect size of 0.9 was statistically significant and there was no evidence of publication bias. Larger MPH effect sizes were associated with physician ratings of outcome and use of higher doses. When treatment is optimized to high doses, the effect size for MPH in adults was 1.3. We found strong support for the assertion that MPH is efficacious for treating adult ADHD. Because the degree of efficacy of MPH in treating ADHD adults is similar to what has been reported from meta-analyses of the child and adolescent literature, our work provides further assurance to clinicians that the diagnosis of ADHD can be validly applied in adulthood.

Methylphenidate improves response inhibition in adults with attention-deficit/hyperactivity disorder

BACKGROUND

Response inhibition is an executive function that requires voluntary control over responses when there is a change of context. The right inferior frontal cortex is necessary for response inhibition, and a deficit in right frontostriatal circuitry might underlie attention-deficit/hyperactivity disorder (ADHD). Many studies of childhood ADHD have demonstrated impaired response inhibition and its amelioration by methylphenidate (MPH). The current study tested response inhibition and the effect of MPH in adult ADHD.

METHODS

Response inhibition was assessed with the "tracking" stop-signal test in 13 adults with a diagnosis of ADHD, both while taking and while not taking medication, and 13 healthy, unmedicated, age- and intelligence quotient-matched control subjects.

RESULTS

Stop-signal reaction time was significantly slower in unmedicated adults with ADHD relative to healthy control subjects, and this deficit was significantly ameliorated by medication.

CONCLUSIONS

Adult ADHD patients had a response inhibition profile similar to that produced by lesions to the right inferior frontal cortex, which was remedied by stimulant medication.

Cardiovascular effects of methylphenidate in humans are associated with increases of dopamine in brain and of epinephrine in plasma

RATIONALE

The cardiovascular effects of psychostimulant drugs (methylphenidate, amphetamine, cocaine) have been mostly associated with their noradrenergic effects. However, there is some evidence that dopaminergic effects are involved in the cardiovascular actions of these drugs. Here, we evaluated this association in humans.

METHODS

Positron emission tomography (PET) and [(11)C]raclopride, a dopamine (DA) D2 receptor radioligand that competes with endogenous DA for occupancy of the D2 receptors, were used to measure changes in brain DA after different doses of intravenous methylphenidate in 14 healthy subjects. Cardiovascular (heart rate and blood pressure) and catecholamine (plasma epinephrine and norepineprhine) responses were determined in parallel to assess their relationships to methylphenidate-induced changes in brain DA.

RESULTS

Methylphenidate administration significantly increased heart rate, systolic and diastolic blood pressures and epinephrine concentration in plasma. The increases in blood pressure were significantly correlated with methylphenidate-induced increases of DA in striatum (r>0.78, P<0.001) and of plasma epinephrine levels (r>0.82, P<0.0005). In turn methylphenidate-induced DA increases in striatum were correlated with increases of epinephrine in plasma (r=0.85, P<0.0001). Subjects in whom methylphenidate did not increase DA had no change in blood pressure or in plasma epinephrine concentration.

DISCUSSION

These results are consistent with the hypothesis that methylphenidate-induced increases in blood pressure are in part due to its central dopaminergic effects. They also suggest that methylphenidate's pressor effects may be in part mediated by DA-induced increases in peripheral epinephrine.