New formulations of stimulants for attention-deficit hyperactivity disorder: therapeutic potential

New formulations of stimulant medications for the treatment of attention-deficit hyperactivity disorder (ADHD) have been an important focus for pharmaceutical industry research and development over the past decade. In this article, we review and assess the therapeutic potential of five new stimulant formulations (one immediate release and four longer-acting preparations) that have recently become available for the treatment of ADHD.While the therapeutic potential of immediate-release enantiomers of methylphenidate has not yet been clinically realised, new long-acting formulations of stimulants have changed the standard of care for children, adolescents and adults with ADHD. The longer duration of action of these once-daily compounds, and the consequent expansion of the duration of daily ADHD coverage afforded by them, has introduced the realistic possibility of reducing the overall daily burden of ADHD on affected individuals. Although more expensive, these new stimulant formulations are easier for patients to use than older stimulants, more resistant to abuse and misuse, and allow for increased privacy of ADHD treatment at school or work.     

Emerging drugs for attention-deficit/hyperactivity disorder

Symptoms of attention-deficit/hyperactivity disorder (ADHD) are heterogeneous and often accompanied by comorbid psychiatric disorders. Although symptoms tend to lessen with age, many patients continue to be affected by the disorder into adulthood. Although many medications are available to treat ADHD, it is unlikely that a single medication will ever be developed to work for all patients. Recent advances, such as long-acting, extended-release formulations and transdermal delivery systems, have lengthened the duration of effectiveness, which has increased compliance and eliminated the need for additional medication dosing during the school or work day. Additional safe, well-tolerated, long-acting medications with further reduced potential for diversion and abuse are needed. Catecholamine pathways and their effect on executive functions and ADHD symptom control have been productive areas of research. Potential therapies such as adrenergic receptor agonists, glutamatergic agents, GABA receptor antagonists and nicotine receptor agonists are being explored as future pharmacotherapies for ADHD.     

The role of stimulants in the treatment of preschool children with attention-deficit hyperactivity disorder

The symptoms of attention-deficit hyperactivity disorder (ADHD) can have an early onset, beginning before the age of 6 years. Despite the significant number of preschool-aged children that can be diagnosed with ADHD, there are limited controlled data available on the pharmacological interventions being increasingly used in this population. A 1990 review showed that 34% of paediatricians and 15% of family physicians had prescribed psychostimulant medications to preschoolers with ADHD, and pharmacoepidemiological studies indicate growing use of stimulants in preschoolers during the 1990s. Unfortunately, only six controlled trials, with a total enrollment of less than 200 children, have been conducted using these drugs in preschoolers. While these small studies provide some evidence of benefit from the use of methylphenidate in preschoolers with ADHD, more data are critically needed.Practice parameters developed by the American Academy of Child & Adolescent Psychiatry and the American Academy of Pediatrics provide some guidance regarding the diagnosis and treatment of young children with ADHD, but are mainly based upon research in children of primary-school age. The ongoing PATS (Preschool ADHD Treatment Study), funded by the National Institute of Mental Health, will provide important clinical guidance for diagnostic considerations and intervention strategies for children with ADHD aged 3-5 years. Pending the release of data from the PATS study, clinicians must rely on developmental assessment skills, available standardised rating instruments, reports about the child from multiple informants, and knowledge of the risks and benefits of available pharmacological and behavioural treatments, in order to treat preschool children with ADHD effectively.     

Long-term changes in management following n-of-1 trials of stimulants in attention-deficit/hyperactivity disorder

Objective Our objective was to evaluate the long-term impact of n-of-1 trials—within-patient randomised, double-blind, cross-over comparisons of stimulant versus placebo or stimulant—on ADHD management. Methods Telephone surveys at 3, 6 and 12 months. Main outcome measures included (1) changes in treatment before and after the n-of-1 trial, (2) congruence of management at follow-up with trial result, (3) reasons for any non-congruence, and (4) persistence of the joint patient-doctor decision over 12 months. Patients were children with clinically diagnosed ADHD, aged 5–16 years. Results A total of 76 patients were followed up; 12 months’ data were available for 67 (88%). Management changed from baseline for 46, 48 and 51% at 3, 6 and 12 months respectively. Most responders, 21/37 (57%), remained on the same stimulant at 12 months, compared to 9/24 (37%) non-responders. Of the remaining non-responders, 15/24 (62%) either switched (2/24, 8%) or ceased stimulants (13/24, 54%). The rate of congruence with the test result was 45/65 (69%) at 3 months, 44/67 (66%) at 6 months and 40/67 (60%) at 12 months. Persistence with the post-trial decision over 12 months was high (79–85%) whether the decision was to continue or to cease stimulants. Conclusions Although not conclusive because there was no control group, our results suggest that n-of-1 trials may improve rational treatment of ADHD.     

Animal models of attention-deficit/hyperactivity disorder

Attention-deficit hyperactivity disorder (AD/HD) is a clinically heterogenous disorder including hyperactivity, impulsivity, and inattention. Both psychostimulant and non-psychostimulant drugs such as methylphenidate and atomoxetine, respectively, to modulate catecholeamine neurotransmission are used as current pharmacotherapies for AD/HD. Multiple lines of evidence suggest that genetic factors play major roles in the etiology of AD/HD. meta-Analyses and pooled data analyses have suggested associations between AD/HD and polymorphisms in genes encoding monoamine neurotransmission molecules. There has been considerable research on this disorder using genetic, pharmacological, and neuroimaging approaches, and several animal models of AD/HD such as spontaneously hypertensive rat (SHR), dopamine transporter (DAT) knockout mice, coloboma mutant mouse, and Grin1 mutant mouse have been reported. These animal models are valuable tools for investigating molecular, cellular, and behavioral mechanisms as well as the neural development and circuit mechanisms of AD/HD. Here, we review the recent literature on animal models of AD/HD and discuss their advantages and limitations.     

Pharmacokinetic variability of long-acting stimulants in the treatment of children and adults with attention-deficit hyperactivity disorder

Methylphenidate- and amfetamine-based stimulants are first-line pharmacotherapies for attention-deficit hyperactivity disorder, a common neurobehavioural disorder in children and adults. A number of long-acting stimulant formulations have been developed with the aim of providing once-daily dosing, employing various means to extend duration of action, including a transdermal delivery system, an osmotic-release oral system, capsules with a mixture of immediate- and delayed-release beads, and prodrug technology. Coefficients of variance of pharmacokinetic measures can estimate the levels of pharmacokinetic variability based on the measurable variance between different individuals receiving the same dose of stimulant (interindividual variability) and within the same individual over multiple administrations (intraindividual variability). Differences in formulation clearly impact pharmacokinetic profiles. Many medications exhibit wide interindividual variability in clinical response. Stimulants with low levels of inter- and intraindividual variability may be better suited to provide consistent levels of medication to patients. The pharmacokinetic profile of stimulants using pH-dependent bead technology can vary depending on food consumption or concomitant administration of medications that alter gastric pH. While delivery of methylphenidate with the transdermal delivery system would be unaffected by gastrointestinal factors, intersubject variability is nonetheless substantial. Unlike the beaded formulations and, to some extent (when considering total exposure) the osmotic-release formulation, systemic exposure to amfetamine with the prodrug stimulant lisdexamfetamine dimesylate appears largely unaffected by such factors, likely owing to its dependence on systemic enzymatic cleavage of the precursor molecule, which occurs primarily in the blood involving red blood cells. The high capacity but as yet unidentified enzymatic system for conversion of lisdexamfetamine dimesylate may contribute to its consistent pharmacokinetic profile. The reasons underlying observed differential responses to stimulants are likely to be multifactorial, including pharmacodynamic factors. While the use of stimulants with low inter- and intrapatient pharmacokinetic variability does not obviate the need to titrate stimulant doses, stimulants with low intraindividual variation in pharmacokinetic parameters may reduce the likelihood of patients falling into subtherapeutic drug concentrations or reaching drug concentrations at which the risk of adverse events increases. As such, clinicians are urged both to adjust stimulant doses based on therapeutic response and the risk for adverse events and to monitor patients for potential causes of pharmacokinetic variability.     

Nicotine effects on adults with attention-deficit/hyperactivity disorder

Several lines of evidence suggest that nicotine may be useful in treating the symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD). The current study was an acute, placebo-controlled double-blind experiment to determine whether nicotine might be useful as an alternative treatment of adults with ADHD symptomatology. Six smokers and 11 nonsmokers who were outpatient referrals for ADHD were diagnosed by DSM-IV criteria. Measures of treatment effect included the Clinical Global Impressions (CGI) scale, Hopkins' symptom check list (SCL-90-R), the Profile of Mood States (POMS), Conners' computerized Continuous Performance Test (CPT), the Stroop test, and an interval-timing task. The smokers underwent overnight deprivation from smoking and were given a 21 mg/day nicotine skin patch for 4.5 h during a morning session. The nonsmokers were given a 7 mg/day nicotine skin patch for 4.5 h during a morning session. Active and placebo patches were given in a counterbalanced order approximately 1 week apart. Nicotine caused a significant overall nicotine-induced improvement on the CGI. This effect was significant when only the nonsmokers were considered, which indicated that it was not due merely to withdrawal relief. Nicotine caused significantly increased vigor as measured by the POMS test. Nicotine caused an overall significant reduction in reaction time (RT) on the CPT, as well as, with the smokers, a significant reduction in another index of inattention, variability in reaction time over trial blocks. Nicotine improved accuracy of time estimation and lowered variability of time-estimation response curves. Because improvements occurred among nonsmokers, the nicotine effect appears not to be merely a relief of withdrawal symptoms. It is concluded that nicotine deserves further clincal trials with ADHD.     

Drug therapy for adults with attention-deficit hyperactivity disorder

Practitioners are increasingly called upon to diagnose and treat attention deficit hyperactivity disorder (ADHD) in adults. Although the use of pharmacotherapy in children with ADHD is well studied, the use of drugs for the treatment of adults with ADHD remains less well established.A systematic review of the literature identified 15 studies (n = 482 patients) of stimulants, and 27 studies of nonstimulant medications (n = 1179 subjects) including antidepressants, norepinephrine reuptake inhibitors, antihypertensive agents, amino acids and wake-promoting agents for the treatment of ADHD in adults.Controlled clinical trials in adults showed that stimulants, antidepressants and norepinephrine reuptake inhibitors demonstrated significant short-term improvements in ADHD symptoms compared with placebo. The two longer term trials with methylphenidate in adults confirmed the ongoing effectiveness and tolerability of stimulants. The response to amphetamine and methylphenidate appears to be dose-dependent. Methylphenidate and amphetamine had an immediate onset of action, whereas responses to pemoline, antidepressants and norepinephrine reuptake inhibitors appeared delayed. Controlled data on nicotinic/cholinergic compounds appear promising. Considerable variability was found in the diagnostic criteria for ADHD in adults, drug dosages and response rates between the various studies.Under controlled conditions, the aggregate literature comprised mainly of short-term studies, shows that stimulants, norepinephrine reuptake inhibitors and specific antidepressants had clinically and statistically significant beneficial effects in the treatment of ADHD in adults. Cholinergic agents appear promising. Further studies are necessary to evaluate the long-term effectiveness and tolerability of various agents, functional and neuropsychological outcomes, and the use of various agents in specific subgroups of adults with ADHD.     

New drugs for treatment of attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is one of the longest recognised and most common neuropsychiatric disorders of childhood. Recent research indicates that ADHD is most often a lifelong condition associated with significant impairment in multiple domains of functioning. ADHD is a clinical diagnosis made on the basis of history and clinical examination. Current molecular, neuroimaging and neuropsychological studies have greatly elucidated our understanding of the basic science of ADHD. The underlying pathophysiology of ADHD has been theorised to be dysregulation of inhibitory noradrenergic frontocortical activity on dopaminergic striatal structures. Pharmacotherapy is recognised as the most effective component of ADHD treatment, although some role exists for proper educational placement, parent management training and social skills development. Methylphenidate and amphetamine are the current standards in ADHD medication treatment. Other medication classes such as tricyclic antidepressants and certain antihypertensives are also used in off-label therapy. Anticipated improvements in new ADHD medications include the development of extended release delivery systems, improved tolerability, alternative mechanisms of action and enhanced efficacy in treatment refractory cases.     

Pozanicline for the treatment of attention-deficit/hyperactivity disorder

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is the most common neurobehavioral disorder occurring in childhood and often continues into adolescence and adulthood. The pathophysiology of ADHD is complex and likely involves multiple neurotransmitter systems. Medications currently used for the treatment of ADHD enhance dopaminergic and/or noradrenergic transmission. However, none of these drugs target the cholinergic system, which is also thought to play a significant role in cognitive disturbances such as those found in ADHD.

Areas covered: In this review, the authors briefly discuss the cholinergic system, including multiple neuronal nicotinic receptor (NNR) subtypes that mediate the positive and negative effects of nicotine, in the context of animal models of ADHD. They also discuss the pharmacology of the NNR pozanicline, a partial agonist with high in vitro binding affinity and selectivity for the α₄β₂ NNR subtype. Finally, the authors examine pozanicline’s clinical developments.

Expert opinion: Pozanicline was shown to be effective in a pilot study in humans with ADHD, but larger trials were negative. Developing an efficacious therapy is difficult. ADHD is a complex disorder with an unknown cause, and it is unclear, at this time, which qualities from NNR agonists are needed to treat it. It is therefore necessary to develop a more enhanced understanding of the nicotinic cholinergic system and its role in ADHD. Furthermore, new research paradigms may need to be employed to find drugs that are effective in patients with ADHD.     

Evidence-based pharmacotherapy for attention-deficit hyperactivity disorder

There is a substantial body of literature documenting the efficacy of multiple unrelated pharmacological agents in attention-deficit hyperactivity disorder (ADHD) individuals throughout the life-cycle. The available literature indicates the important role of psychopharmacological agents in the reduction of the core symptoms of ADHD and associated impairments. The literature documents that stimulants not only improve abnormal behaviours of ADHD, but also improves self-esteem, cognition, and social and family function. However, response varied in different age groups and with certain comorbidities. In addition there is a large body of literature documenting the efficacy of atomoxetine which shows improvement in these same domains. More research is needed on alternative pharmacological treatments and to further evaluate established therapeutics beyond school-aged Caucasian boys. Further, more research is needed on the efficacy of treatment for comorbid ADHD, use of combined medications, and the combination of medication and psychosocial treatment.     

Methylphenidate transdermal system: clinical applications for attention-deficit/hyperactivity disorder

The methylphenidate transdermal system (MTS) provides a novel method of delivery for methylphenidate, a well-studied and effective medication for attention-deficit/hyperactivity disorder. The MTS achieves two major goals. First, the delivery system allows for administration throughout the day with a single patch, thus improving adherence. Second, it is the first approved attention-deficit/hyperactivity disorder medication that is not administered orally, thus bypassing gastrointestinal absorption and first-pass metabolism through the enteric circulation. In this article, we review the current data on MTS, including preclinical, clinical and post-marketing studies, and compare efficacy and tolerability to currently available treatments.     

Methylphenidate transdermal system: clinical applications for attention-deficit/hyperactivity disorder

The methylphenidate transdermal system (MTS) provides a novel method of delivery for methylphenidate, a well-studied and effective medication for attention-deficit/hyperactivity disorder. The MTS achieves two major goals. First, the delivery system allows for administration throughout the day with a single patch, thus improving adherence. Second, it is the first approved attention-deficit/hyperactivity disorder medication that is not administered orally, thus bypassing gastrointestinal absorption and first-pass metabolism through the enteric circulation. In this article, we review the current data on MTS, including preclinical, clinical and post-marketing studies, and compare efficacy and tolerability to currently available treatments.     

Treating common psychiatric disorders associated with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) often occurs along with other psychiatric disorders, with estimated comorbidity rates of 50--90%. Comorbidity greatly influences presentation, diagnosis and prognosis, complicates treatment and significantly increases the morbidity and disease burden of ADHD. Commonly co-occurring psychiatric disorders are disruptive behavior disorder, anxiety, depression, bipolar disorder and substance use disorders. This article provides a brief review of effective strategies for treating the most common psychiatric disorders associated with ADHD. This paper also discusses knowledge gaps in the understanding of treatment of comorbid disorders associated with ADHD, and directions for future research.     

New drugs for the treatment of attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is the most common neuropsychiatric disorder of childhood. Recent research indicates that ADHD most often persists into adolescence and adulthood, and is associated with impairments in academic, social and occupational functioning. The ADHD diagnosis is based on history and clinical examination. There are no objective laboratory measures for diagnosis. ADHD is largely heritable. Its underlying pathophysiology has been theorised to include dysregulation of inhibitory noradrenergic frontocortical activity on dopaminergic striatal structures. Evidence shows that ADHD is highly responsive to pharmacological treatments resulting in global functional improvements. Although pharmacotherapy is recognised as the most effective treatment, additional components to optimise ADHD management include proper educational placement, parent management training and social skills development. Central nervous system stimulants, specifically methylphenidate and amphetamine, remain first-line pharmacological treatments. Atomoxetine, a selective noradrenergic re-uptake inhibitor, is the first non-stimulant compound to receive FDA approval for paediatric and adult ADHD. Other medication classes, including alpha-agonist antihypertensives, tricyclic antidepressants, other antidepressants such as buproprion, and the wake-promoting agent modafinil, are prescribed in off-label therapy. Ongoing development of new ADHD medications is expected to emphasise alternative and extended-release delivery systems and non-stimulant compounds.     

Pharmacological treatment of attention-deficit/hyperactivity disorder: assessing outcomes

A substantial body of evidence has supported the efficacy and safety of pharmacological treatment available for attention deficit/hyperactivity disorder (ADHD). There is increasing agreement that the important treatment outcomes for ADHD extend beyond improvement in core symptoms and that a more generic (or global) concept of remission is the overarching goal of treatment. However, there is no consensus on the best definition of remission or on how best to conceptualize and measure broader treatment outcomes. In this article, we provide an overview of the various methods and approaches to measuring treatment outcomes for ADHD with respect to symptoms, impairment, quality of life, adverse events and safety as well as cognition. We will describe the ways that they may be used within routine clinical practice and think ahead about the kinds of studies that are required to move the field forward.     

Clonidine extended-release: in attention-deficit hyperactivity disorder

Clonidine, an α(2)-adrenergic agonist, is approved in the US as an extended-release (XR) tablet for the treatment of attention-deficit hyperactivity disorder (ADHD) in children and adolescents (aged 6-17 years). In two, randomized, double-blind, multicenter, phase III trials of 8 weeks' duration, clonidine XR improved the symptoms of ADHD in children and adolescents. Significantly greater reductions from baseline in ADHD rating scale IV (ADHD-RS-IV) total scores at week 5 (primary endpoint) were achieved by recipients of clonidine XR 0.2 and 0.4?mg/day monotherapy than by recipients of placebo. When added to patients' normal stimulant regimen, significantly greater reductions from baseline in ADHD-RS-IV total scores at week 5 (primary endpoint) were achieved with a flexible dose of clonidine XR 0.1-0.4?mg/day than with placebo. Symptomatic improvement of ADHD was achieved following 2 weeks' treatment with clonidine XR. In both trials, significantly greater reductions from baseline in ADHD-RS-IV total scores were apparent at week 2 onwards for recipients of clonidine XR than for recipients of placebo. Clonidine XR was generally well tolerated as monotherapy and as adjunctive therapy with stimulant regimens in clinical trials in children and adolescents.     

Drugs under investigation for attention-deficit hyperactivity disorder

There has been substantial development of pharmacological treatments for attention-deficit hyperactivity disorder (ADHD) recently. The greatest change is the approval of new delivery systems for methylphenidate (MPH) and amphetamine (AMP) that permit once a day dosing. There are also a number of new compounds under development for the disorder, including several non-stimulant agents. These compounds target the noradrenergic, histaminergic and dopaminergic systems. The recent developments in the pharmacological treatment of ADHD should increase therapeutic options and the percentage of individuals with the disorder who can be effectively treated.