Methylphenidate and its isomers: their role in the treatment of attention-deficit hyperactivity disorder using a transdermal delivery system

Memory loss induced by lisdexamfetamine in the rat: A behavioral, electrophysiological, and histopathological Study

Lisdexamfetamine (LDX) is one of the drugs commonly used to treat attention deficit hyperactivity disorder (ADHD). However, its neurological side effects, particularly on cognition, are not fully understood. The present study focused on memory in rats treated with four weeks of LDX injection. We compared LDX-treated rats with control ones, using several methods to evaluate the behavioral responses and electrophysiological, molecular, and histological properties in the hippocampus. Our findings demonstrated that subchronic administration of LDX impaired behavioral performance in all memory assessment tests (Y maze, Morris Water Maze, and Shuttle box). Although LDX did not alter population spike (PS) amplitude, it increased the field excitatory postsynaptic potential (fEPSP) slope of evoked potentials of LTP components. Also, in addition to an increase in expression of caspase-3 in the hippocampus, which indicates the susceptibility to apoptosis in LDX-treated rats, the number of microglia and astrocytes went up significantly in the LDX group. Moreover, Sholl's analysis showed an increase in the soma size and total process length in both hippocampal astrocytes and microglia. Overall, because of these destructive effects of LDX on the hippocampus, which is one of the critical memory-related areas of the brain, the findings of this investigation provide evidence to show the disruption of memory-related variables following the LDX. However, more research is needed to clarify it.

Stimulant prodrugs: A pharmacological and clinical assessment of their role in treating ADHD and binge-eating disorder

In this review, we critically evaluate the contribution of prodrugs to treating two related psychiatric disorders, attention-deficit hyperactivity disorder (ADHD) and binge-eating disorder (BED). ADHD is characterized by inattentiveness, distractibility, impulsiveness, and hyperactivity. BED is also an impulse-control disorder which leads to frequent, compulsive episodes of excessive eating (binges). Lisdexamfetamine (LDX; prodrug of d-amphetamine) is approved to treat both ADHD and BED. Serdexmethylphenidate (SDX; prodrug of d-threo-methylphenidate) is not clinically approved as monotherapy but, in a fixed-dose combination with immediate release d-threo-methylphenidate (Azstarys™), SDX is approved for managing ADHD in children/adolescents. The pharmacological actions of a stimulant mediate both its efficacy and side-effects. Therefore, daily management of ADHD or BED to maintain optimum efficacy and tolerability places highly restrictive requirements on the pharmacokinetic/pharmacodynamic (PK/PD) characteristics of stimulant medications, especially prodrugs. Prodrugs must have good bioavailability and rapid metabolism to provide therapeutic efficacy soon after morning dosing combined with providing stimulant coverage throughout the day/evening. A wide selection of dosages and linear PK for the prodrug and its active metabolite are essential requirements for treatment of these conditions. The proposed neurobiological causes of ADHD and BED are described. The chemical, pharmacological and PK/PD properties responsible for the therapeutic actions of the prodrugs, LDX and SDX, are compared and contrasted. Finally, we critically assess their contribution as ADHD and BED medications, including advantages over their respective active metabolites, d-amphetamine and d-threo-methylphenidate, and also their potential for misuse and abuse.

The Tungsten-Promoted Synthesis of Piperidyl-Modified erythro-Methylphenidate Derivatives

Due to its efficacy as a dopamine receptor agonist, methylphenidate (MPH) is of interest as a potential therapeutic for cocaine addiction. While numerous derivatives of MPH have been investigated for their potential medicinal value, functionalization of the piperidine ring has not been explored. The pyridine borane ligand in WTp(NO)(PMe3)(η2-pyBH3) is dearomatized by the metal and can be elaborated to the analogous η2-mesylpyridinium complex. Installing a methyl phenylacetate moiety at the C2' position via a Reformatsky reaction followed by a tandem protonation/nucleophilic addition sequence results in a library of erythro MPH analogues functionalized at the piperidyl C5' position. The functional group is added chemoselectively to C5', cis to the methyl phenylacetate. Repeating this procedure with an enantioenriched source of the tungsten reagent results in enantioenriched MPH derivatives. All identities of the newly reported compounds are supported by comprehensive 2D NMR and HRMS data or crystallographic data.

Adrenoceptors: A Focus on Psychiatric Disorders and Their Treatments

Research into the involvement of adrenoceptor subtypes in the cause(s) of psychiatric disorders is particularly challenging. This is partly because of difficulties in developing animal models that recapitulate the human condition but also because no evidence for any causal links has emerged from studies of patients. These, and other obstacles, are outlined in this chapter. Nevertheless, many drugs that are used to treat psychiatric disorders bind to adrenoceptors to some extent. Direct or indirect modulation of the function of specific adrenoceptor subtypes mediates all or part of the therapeutic actions of drugs in various psychiatric disorders. On the other hand, interactions with central or peripheral adrenoceptors can also explain their side effects. This chapter discusses both aspects of the field, focusing on disorders that are prevalent: depression, schizophrenia, anxiety, attention-deficit hyperactivity disorder, binge-eating disorder, and substance use disorder. In so doing, we highlight some unanswered questions that need to be resolved before it will be feasible to explain how changes in the function of any adrenoceptor subtype affect mood and behavior in humans and other animals.

Methylphenidate for children and adolescents with attention deficit hyperactivity disorder (ADHD)

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is one of the most commonly diagnosed and treated psychiatric disorders in childhood. Typically, children and adolescents with ADHD find it difficult to pay attention and they are hyperactive and impulsive. Methylphenidate is the psychostimulant most often prescribed, but the evidence on benefits and harms is uncertain. This is an update of our comprehensive systematic review on benefits and harms published in 2015.

OBJECTIVES

To assess the beneficial and harmful effects of methylphenidate for children and adolescents with ADHD.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, three other databases and two trials registers up to March 2022. In addition, we checked reference lists and requested published and unpublished data from manufacturers of methylphenidate.

SELECTION CRITERIA

We included all randomised clinical trials (RCTs) comparing methylphenidate versus placebo or no intervention in children and adolescents aged 18 years and younger with a diagnosis of ADHD. The search was not limited by publication year or language, but trial inclusion required that 75% or more of participants had a normal intellectual quotient (IQ > 70). We assessed two primary outcomes, ADHD symptoms and serious adverse events, and three secondary outcomes, adverse events considered non-serious, general behaviour, and quality of life.

DATA COLLECTION AND ANALYSIS

Two review authors independently conducted data extraction and risk of bias assessment for each trial. Six review authors including two review authors from the original publication participated in the update in 2022. We used standard Cochrane methodological procedures. Data from parallel-group trials and first-period data from cross-over trials formed the basis of our primary analyses. We undertook separate analyses using end-of-last period data from cross-over trials. We used Trial Sequential Analyses (TSA) to control for type I (5%) and type II (20%) errors, and we assessed and downgraded evidence according to the GRADE approach.

MAIN RESULTS

We included 212 trials (16,302 participants randomised); 55 parallel-group trials (8104 participants randomised), and 156 cross-over trials (8033 participants randomised) as well as one trial with a parallel phase (114 participants randomised) and a cross-over phase (165 participants randomised). The mean age of participants was 9.8 years ranging from 3 to 18 years (two trials from 3 to 21 years). The male-female ratio was 3:1. Most trials were carried out in high-income countries, and 86/212 included trials (41%) were funded or partly funded by the pharmaceutical industry. Methylphenidate treatment duration ranged from 1 to 425 days, with a mean duration of 28.8 days. Trials compared methylphenidate with placebo (200 trials) and with no intervention (12 trials). Only 165/212 trials included usable data on one or more outcomes from 14,271 participants. Of the 212 trials, we assessed 191 at high risk of bias and 21 at low risk of bias. If, however, deblinding of methylphenidate due to typical adverse events is considered, then all 212 trials were at high risk of bias.

PRIMARY OUTCOMES

methylphenidate versus placebo or no intervention may improve teacher-rated ADHD symptoms (standardised mean difference (SMD) -0.74, 95% confidence interval (CI) -0.88 to -0.61; I² = 38%; 21 trials; 1728 participants; very low-certainty evidence). This corresponds to a mean difference (MD) of -10.58 (95% CI -12.58 to -8.72) on the ADHD Rating Scale (ADHD-RS; range 0 to 72 points). The minimal clinically relevant difference is considered to be a change of 6.6 points on the ADHD-RS. Methylphenidate may not affect serious adverse events (risk ratio (RR) 0.80, 95% CI 0.39 to 1.67; I² = 0%; 26 trials, 3673 participants; very low-certainty evidence). The TSA-adjusted intervention effect was RR 0.91 (CI 0.31 to 2.68).

SECONDARY OUTCOMES

methylphenidate may cause more adverse events considered non-serious versus placebo or no intervention (RR 1.23, 95% CI 1.11 to 1.37; I² = 72%; 35 trials 5342 participants; very low-certainty evidence). The TSA-adjusted intervention effect was RR 1.22 (CI 1.08 to 1.43). Methylphenidate may improve teacher-rated general behaviour versus placebo (SMD -0.62, 95% CI -0.91 to -0.33; I² = 68%; 7 trials 792 participants; very low-certainty evidence), but may not affect quality of life (SMD 0.40, 95% CI -0.03 to 0.83; I² = 81%; 4 trials, 608 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

The majority of our conclusions from the 2015 version of this review still apply. Our updated meta-analyses suggest that methylphenidate versus placebo or no-intervention may improve teacher-rated ADHD symptoms and general behaviour in children and adolescents with ADHD. There may be no effects on serious adverse events and quality of life. Methylphenidate may be associated with an increased risk of adverse events considered non-serious, such as sleep problems and decreased appetite. However, the certainty of the evidence for all outcomes is very low and therefore the true magnitude of effects remain unclear. Due to the frequency of non-serious adverse events associated with methylphenidate, the blinding of participants and outcome assessors is particularly challenging. To accommodate this challenge, an active placebo should be sought and utilised. It may be difficult to find such a drug, but identifying a substance that could mimic the easily recognised adverse effects of methylphenidate would avert the unblinding that detrimentally affects current randomised trials. Future systematic reviews should investigate the subgroups of patients with ADHD that may benefit most and least from methylphenidate. This could be done with individual participant data to investigate predictors and modifiers like age, comorbidity, and ADHD subtypes.

Behavioral, Neurochemical and Developmental Effects of Chronic Oral Methylphenidate: A Review

The majority of animal studies on methylphenidate (MP) use intraperitoneal (IP) injections, subcutaneous (SC) injections, or the oral gavage route of administration. While all these methods allow for delivery of MP, it is the oral route that is clinically relevant. IP injections commonly deliver an immediate and maximum dose of MP due to their quick absorption. This quick-localized effect can give timely results but will only display a small window of the psychostimulant's effects on the animal model. On the opposite side of the spectrum, a SC injection does not accurately represent the pathophysiology of an oral exposure because the metabolic rate of the drug would be much slower. The oral-gavage method, while providing an oral route, possesses some adverse effects such as potential animal injury and can be stressful to the animal compared to voluntary drinking. It is thus important to allow the animal to have free consumption of MP, and drinking it to more accurately mirror human treatment. The use of a two-bottle drinking method allows for this. Rodents typically have a faster metabolism than humans, which means this needs to be considered when administering MP orally while reaching target pharmacokinetic levels in plasma. With this oral two-bottle approach, the pathophysiological effects of MP on development, behavior, neurochemistry and brain function can be studied. The present review summarizes these effects of oral MP which have important implications in medicine.

Effect of methylphenidate on functional controllability: a preliminary study in medication-naïve children with ADHD

Methylphenidate (MPH) is the recommended first-line treatment for attention-deficit/hyperactivity disorder (ADHD). While MPH's mechanism of action as a dopamine and noradrenaline transporter blocker is well known, how this translates to ADHD-related symptom mitigation is still unclear. As functional connectivity is reliably altered in ADHD, with recent literature indicating dysfunctional connectivity dynamics as well, one possible mechanism is through altering brain network dynamics. In a double-blind, placebo-controlled MPH crossover trial, 19 medication-naïve children with ADHD underwent two functional MRI scanning sessions (one on MPH and one on placebo) that included a resting state scan and two inhibitory control tasks; 27 typically developing (TD) children completed the same protocol without medication. Network control theory, which quantifies how brain activity reacts to system inputs based on underlying connectivity, was used to assess differences in average and modal functional controllability during rest and both tasks between TD children and children with ADHD (on and off MPH) and between children with ADHD on and off MPH. Children with ADHD on placebo exhibited higher average controllability and lower modal controllability of attention, reward, and somatomotor networks than TD children. Children with ADHD on MPH were statistically indistinguishable from TD children on almost all controllability metrics. These findings suggest that MPH may stabilize functional network dynamics in children with ADHD, both reducing reactivity of brain organization and making it easier to achieve brain states necessary for cognitively demanding tasks.

Neuroprotection in late life attention-deficit/hyperactivity disorder: A review of pharmacotherapy and phenotype across the lifespan

For decades, psychostimulants have been the gold standard pharmaceutical treatment for attention-deficit/hyperactivity disorder (ADHD). In the United States, an astounding 9% of all boys and 4% of girls will be prescribed stimulant drugs at some point during their childhood. Recent meta-analyses have revealed that individuals with ADHD have reduced brain volume loss later in life (>60 y.o.) compared to the normal aging brain, which suggests that either ADHD or its treatment may be neuroprotective. Crucially, these neuroprotective effects were significant in brain regions (e.g., hippocampus, amygdala) where severe volume loss is linked to cognitive impairment and Alzheimer's disease. Historically, the ADHD diagnosis and its pharmacotherapy came about nearly simultaneously, making it difficult to evaluate their effects in isolation. Certain evidence suggests that psychostimulants may normalize structural brain changes typically observed in the ADHD brain. If ADHD itself is neuroprotective, perhaps exercising the brain, then psychostimulants may not be recommended across the lifespan. Alternatively, if stimulant drugs are neuroprotective, then this class of medications may warrant further investigation for their therapeutic effects. Here, we take a bottom-up holistic approach to review the psychopharmacology of ADHD in the context of recent models of attention. We suggest that future studies are greatly needed to better appreciate the interactions amongst an ADHD diagnosis, stimulant treatment across the lifespan, and structure-function alterations in the aging brain.

Plasma Concentrations of Methylphenidate Enantiomers in Adults with ADHD and Substance Use Disorder, with focus on high doses and relationship to Carboxylesterase activity

Scarce data are available on methylphenidate (MPH) plasma concentrations reached after doses higher than 180 mg. The interindividual and intraindividual variability in the exposure of MPH and ritalinic acid (RA) enantiomers was examined in 28 patients with ADHD and substance use disorders, with MPH daily doses between 30 and 600 mg (median 160 mg). MPH and RA plasma concentrations were analysed with an enantioselective LC–MS/MS method. d‐MPH plasma concentration/dose varied 25‐fold between subjects but was reasonably stable within an individual. Twelve subjects had quantifiable l‐MPH plasma concentrations, which accounted for up to 48% of the total MPH plasma concentration. The less active l‐MPH enantiomer could, in individuals with low carboxylesterase 1 (CES1) activity, contribute significantly to the total MPH plasma drug concentration and hamper the estimation of the exposure to the more active d‐MPH enantiomer. However, the high correlation between the total (d + l) RA/MPH metabolic ratio and the d‐RA/d‐MPH metabolic ratio (r_s = 0.94) indicates that the ratio based on non‐enantioselective analysis could be used as a marker of CES1 activity. Whether this holds true for subjects with aberrant metabolism due to genetic variants or during concomitant treatment with inhibitors or inducers of the enzyme remains to be studied.

New Drugs to Treat ADHD: Opportunities and Challenges in Research and Development

Since the landmark MTA (Multimodal Treatment of ADHD) trial unequivocally demonstrated the efficacy of methylphenidate, catecholaminergic drugs, especially stimulants, have been the therapeutic mainstay in treatment of Attention-Deficit Hyperactivity Disorder (ADHD). We review the new drugs which have entered the ADHD formulary. The lessons learned from drug-candidates that have succeeded in clinical trials together with those that have not have also been considered. What emerges confirms and consolidates the hypothesis that clinically effective ADHD drugs indirectly or directly increase catecholaminergic neurotransmission in the prefrontal cortex (PFC). Attempts to enhance catecholaminergic signalling through modulatory neurotransmitter systems or cognitive-enhancing drugs have all failed. New drugs approved for ADHD are catecholaminergic reuptake inhibitors and releasing agents, or selective noradrenaline reuptake inhibitors. Triple reuptake inhibitors with preferential effects on dopamine have not been successful. The substantial number of failures probably accounts for a continued focus on developing novel catecholaminergic and noradrenergic drugs, and a dearth of drug-candidates with novel mechanisms entering clinical development. However, substantial improvements in ADHD pharmacotherapy have been achieved by the almost exclusive use of once-daily medications and prodrugs, e.g. lisdexamfetamine and Azstarys^®, which improve compliance, deliver greater efficacy and reduce risks for diversion and abuse.

Methylphenidate for attention-deficit/hyperactivity disorder in adults: a narrative review

RATIONALE

Psychostimulants, including methylphenidate (MPH), are the mainstay of pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD) in adults. Even though MPH is the most commonly used medication for ADHD these days, there are relatively few resources available that provide comprehensive insight into the pharmacological and clinical features of the compound.

OBJECTIVE

The aim of this paper is to provide an up-to-date outline of the pharmacology and clinical utility of MPH for ADHD in adult patients.

METHODS

While conducting the narrative review, we applied structured search strategies covering the two major online databases (MEDLINE and Cochrane Central Register of Controlled Trials). In addition, we performed handsearching of reference lists of relevant papers.

RESULTS

Methylphenidate exhibits multimodal mechanism of action, working primarily as a dopamine and noradrenaline reuptake inhibitor. It also protects the dopaminergic system against the ongoing 'wearing off' (by securing a substantial reserve pool of the neurotransmitter, stored in the presynaptic vesicles). In placebo-controlled trials, MPH was shown to be moderately effective both against the core ADHD symptoms (standardized mean difference [SMD], 0.49; 95% confidence interval [CI], 0.35-0.64), and the accompanying emotion regulation deficits (SMD, 0.34; 95% CI, 0.23-0.45). The most common adverse events related to long-term treatment with MPH are decreased appetite (~ 20%), dry mouth (15%), heart palpitations (13%), gastrointestinal infections (~ 10%), and agitation/feeling restless (~ 10%).

CONCLUSIONS

There is substantial body of evidence to suggest that MPH is an effective and safe treatment option for adults with ADHD.

Pharmacology of Drugs Used as Stimulants

Psychostimulant, cardiovascular, and temperature actions of stimulants involve adrenergic (norepinephrine), dopaminergic (dopamine), and serotonergic (serotonin) pathways. Stimulants such as amphetamine, 3,4-methylenedioxymethamphetamine (MDMA), or mephedrone can act on the neuronal membrane monoamine transporters NET, DAT, and SERT and/or the vesicular monoamine transporter 2 to inhibit reuptake of neurotransmitter or cause release by reverse transport. Stimulants may have additional effects involving pre- and postsynaptic/junctional receptors for norepinephrine, dopamine, and serotonin and other receptors. As a result, stimulants may have a wide range of possible actions. Agents with cocaine or MDMA-like actions can induce serious and potentially fatal adverse events via thermodysregulatory, cardiovascular, or other mechanisms. MDMA-like stimulants may cause hyperthermia that can be life threathening. Recreational users of stimulants should be aware of the dangers of hyperthermia in a rave/club environment.

Lifetime evolution of ADHD treatment

Attention-deficit hyperactivity disorder (ADHD), has been traditionally considered a neurodevelopmental disorder affecting children and adolescents characterized by inattention, hyperactivity, disruptive behavior, and impulsivity. Although still debated, it is evident that ADHD is also present in adulthood, but this diagnosis is rarely carried out, mainly for the frequent comorbidity with other psychiatric and/or substance abuse disorders. Given the need to shed more light on the pharmacological treatment of ADHD, we performed a naturalistic review to review and comment on the available literature of ADHD treatment across the lifespan. Indeed, stimulants are endowed of a prompt efficacy and safety, whilst non-stimulants, although requiring some weeks to be fully effective, are useful when a substance abuse history is detected. In any case, the pharmacological management of ADHD appears to be still largely influenced by the individual experience of the clinicians. Further longitudinal studies with a careful and detailed characterization of participants across different phases of the lifespan are also required to provide relevant confirmations (or denials) regarding pharmacological treatments amongst the different age groups.

Cardiovascular and temperature adverse actions of stimulants

The vast majority of illicit stimulants act at monoaminergic systems, causing both psychostimulant and adverse effects. Stimulants can interact as substrates or antagonists at the nerve terminal monoamine transporter that mediates the reuptake of monoamines across the nerve synaptic membrane and at the vesicular monoamine transporter (VMAT-2) that mediates storage of monoamines in vesicles. Stimulants can act directly at presynaptic or postsynaptic receptors for monoamines or have indirect monoamine-mimetic actions due to the release of monoamines. Cocaine and other stimulants can acutely increase the risk of sudden cardiac death. Stimulants, particularly MDMA, in hot conditions, such as that occurring at a "rave," have caused fatalities from the consequences of hyperthermia, often compounding cardiac adverse actions. This review examines the pharmacology of the cardiovascular and temperature adverse actions of stimulants.

α-C-H Bond Functionalization of Unprotected Alicyclic Amines: Lewis-Acid-Promoted Addition of Enolates to Transient Imines

Enolizable cyclic imines, obtained in situ from their corresponding lithium amides by oxidation with simple ketone oxidants, are readily alkylated with a range of enolates to provide mono- and polycyclic β-aminoketones in a single operation, including the natural product (±)-myrtine. Nitrile anions also serve as competent nucleophiles in these transformations, which are promoted by BF3 etherate. β-Aminoesters derived from ester enolates can be converted to the corresponding β-lactams.

Immediate-release methylphenidate for attention deficit hyperactivity disorder (ADHD) in adults

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is characterized by symptoms of inattention or impulsivity or both, and hyperactivity, which affect children, adolescents, and adults. In some countries, methylphenidate is the first option to treat adults with moderate or severe ADHD. However, evidence on the efficacy and adverse events of immediate-release (IR) methylphenidate in the treatment of ADHD in adults is limited and controversial.

OBJECTIVES

To evaluate the efficacy and harms (adverse events) of IR methylphenidate for treating ADHD in adults.

SEARCH METHODS

In January 2020, we searched CENTRAL, MEDLINE, Embase, eight additional databases and three trial registers. We also searched internal reports on the European Medicines Agency and the US Food and Drug Administration websites. We checked citations of included trials to identify additional trials not captured by the electronic searches.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing IR methylphenidate, at any dose, with placebo or other pharmacological interventions (including extended-release formulations of methylphenidate) for ADHD in adults. Primary outcomes comprised changes in the symptoms of ADHD (efficacy) and harms. Secondary outcomes included changes in the clinical impression of severity and improvement, level of functioning, depression, anxiety and quality of life. Outcomes could have been rated by investigators or participants.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently on the characteristics of the trials, participants, interventions; outcomes and financial conflict of interests. We resolved disagreements by discussion or consulting a third review author. We obtained additional, unpublished information from the authors of one included trial that had reported efficacy data in a graph. We calculated mean differences (MDs) or standardized MDs (SMDs) with 95% confidence intervals (CIs) for continuous data reported on the same or different scales, respectively. We summarized dichotomous variables as risk ratios (RRs) with 95% CI.

MAIN RESULTS

We included 10 trials published between 2001 and 2016 involving 497 adults with ADHD. Three trials were conducted in Europe and one in Argentina; the remaining trials did not report their location. The RCTs compared IR methylphenidate with placebo, an osmotic-release oral system (OROS) of methylphenidate (an extended-release formulation), an extended-release formulation of bupropion, lithium, and Pycnogenol® (maritime pine bark extract). Participants comprised outpatients, inpatients in addiction treatment, and adults willing to attend an intensive outpatient program for cocaine dependence. The duration of the follow-up ranged from 6 to 18 weeks. IR methylphenidate versus placebo We found very low-certainty evidence that, compared with placebo, IR methylphenidate may reduce symptoms of ADHD when measured with investigator-rated scales (MD -20.70, 95% CI -23.97 to -17.43; 1 trial, 146 participants; end scores; Adult ADHD Investigator Symptom Report Scale (AISRS), scored from 0 to 54), but the evidence is uncertain. The effect of IR methylphenidate on ADHD symptoms when measured with participant-rated scales was moderate, but the certainty of the evidence is very low (SMD -0.59, 95% CI -1.25 to 0.06; I² = 69%; 2 trials, 138 participants; end scores). There is very low-certainty evidence that, compared with placebo, IR methylphenidate may reduce the clinical impression of the severity of ADHD symptoms (MD -0.57, 95% CI -0.85 to -0.28; 2 trials, 139 participants; I² = 0%; change and end scores; Clinical Global Impression (CGI)-Severity scale (scored from 1 (very much improved) to 7 (very much worse))). There is low-certainty evidence that, compared with placebo, IR methylphenidate may slightly impact the clinical impression of an improvement in symptoms of ADHD (MD -0.94, 95% CI -1.37 to -0.51; 1 trial, 49 participants; end scores; CGI-Improvement scale (scored from 1 (very much improved) to 7 (very much worse))). There is no clear evidence of an effect on anxiety (MD -0.20, 95% CI -4.84 to 4.44; 1 trial, 19 participants; change scores; Hamilton Anxiety Scale (HAM-A; scored from 0 to 56); very low-certainty evidence) or depression (MD 2.80, 95% CI -0.09 to 5.69; 1 trial, 19 participants; change scores; Hamilton Depression Scale (HAM-D; scored from 0 to 52); very low-certainty evidence) in analyses comparing IR methylphenidate with placebo. IR methylphenidate versus lithium Compared with lithium, it is uncertain whether IR methylphenidate increases or decreases symptoms of ADHD (MD 0.60, 95% CI -3.11 to 4.31; 1 trial, 46 participants; end scores; Conners' Adult ADHD Rating Scale (scored from 0 to 198); very low-certainty evidence); anxiety (MD -0.80, 95% CI -4.49 to 2.89; 1 trial, 46 participants; end scores; HAM-A; very low-certainty evidence); or depression (MD -1.20, 95% CI -3.81 to 1.41, 1 trial, 46 participants; end scores; HAM-D scale; very low-certainty evidence). None of the included trials assessed participant-rated changes in symptoms of ADHD, or clinical impression of severity or improvement in participants treated with IR methylphenidate compared with lithium. Adverse events were poorly assessed and reported. We rated all trials at high risk of bias due to selective outcome reporting of harms and masking of outcome assessors (failure to blind outcome assessor to measure adverse events). Overall, four trials with 203 participants who received IR methylphenidate and 141 participants who received placebo described the occurrence of harms. The use of IR methylphenidate in these trials increased the risk of gastrointestinal complications (RR 1.96, 95% CI 1.13 to 2.95) and loss of appetite (RR 1.77, 95% CI 1.06 to 2.96). Cardiovascular adverse events were reported inconsistently, preventing a comprehensive analysis. One trial comparing IR methylphenidate to lithium reported five and nine adverse events, respectively. We considered four trials to have notable concerns of vested interests influencing the evidence, and authors from two trials omitted information related to the sources of funding and conflicts of interest.

AUTHORS' CONCLUSIONS

We found no certain evidence that IR methylphenidate compared with placebo or lithium can reduce symptoms of ADHD in adults (low- and very low-certainty evidence). Adults treated with IR methylphenidate are at increased risk of gastrointestinal and metabolic-related harms compared with placebo. Clinicians should consider whether it is appropriate to prescribe IR methylphenidate, given its limited efficacy and increased risk of harms. Future RCTs should explore the long-term efficacy and risks of IR methylphenidate, and the influence of conflicts of interest on reported effects.

CRISPR/Cas9-induced nos2b mutant zebrafish display behavioral abnormalities

The immunomodulatory function of nitric oxide synthase (NOS2) has been extensively studied. However, some behavioral abnormalities caused by its mutations have been found in a few rodent studies, of which the molecular mechanism remains elusive. In this research, we generated nos2b gene knockout zebrafish (nos2b^sou2/sou2 ) using CRISPR/Cas9 approach and investigated their behavioral and molecular changes by doing a series of behavioral detections, morphological measurements, and molecular analyses. We found that, compared with nos2b^+/+ zebrafish, nos2b^sou2/sou2 zebrafish exhibited enhanced motor activity; additionally, nos2b^sou2/sou2 zebrafish were characterized by smaller brain size, abnormal structure of optic tectum, reduced mRNA level of presynaptic synaptophysin and postsynaptic homer1, and altered response to sodium nitroprusside/methylphenidate hydrochloride treatment. These findings will likely contribute to future studies of behavioral regulation.

Methylphenidate challenge test in adults with attention deficit/hyperactivity disorder (ADHD): Clinical effects and their predictors

OBJECTIVE

Adult and children attention deficit/hyperactivity disorder (ADHD) share similar symptoms and responses to drugs such as methylphenidate (MPH). Yet, in Europe, these drugs remain unlicensed for adults. We aimed to assess the effects of an acute MPH challenge on the four dimensions concentration, impulsivity, tension, and general well-being in ADHD adults, and identify predictors of improvement.

METHODS

Therapeutic Drug Monitoring was performed to measure MPH plasma levels. A Visual Analogue Scale was administered to patients before and after the acute MPH challenge to measure self-reported changes in the four dimensions.

RESULTS

After the acute MPH challenge, our 71 patients showed significant improvement in concentration and tension. The MPH challenge dose correlated with lower patients' age, greater side effects, increased concentration (p = .008) and decreased tension (p = .001). At multiple linear regression MPH plasma levels and absence of postdose side effects predicted concentration improvement, MPH plasma levels predicted tension improvement. MPH plasma levels were significantly higher in patients who reported an improvement in concentration, tension, and impulsivity compared to nonimprovers (p's from .001 to .004).

CONCLUSIONS

These findings point to the efficacy of MPH challenge in improving concentration and tension in adult ADHD, thus emphasizing the need for a broader treatment access for these patients.

ADHD with Comorbid Bipolar Disorders: A Systematic Review of Neurobiological, Clinical and Pharmacological Aspects Across the Lifespan

BACKGROUND

Attention deficit hyperactivity (ADHD) disorder is a neurodevelopmental disorder characterized by inattention, hyperactivity, disruptive behaviour, and impulsivity. Despite considered typical of children for a long time, the persistence of ADHD symptoms in adulthood gained increasing interest during the last decades. Indeed, its diagnosis, albeit controversial, is rarely carried out even because ADHD is often comorbid with several other psychiatric diosrders, in particular with bipolar disorders (BDs), a condition that complicates the clinical picture, assessment and treatment.

AIMS

The aim of this paper was to systematically review the scientific literature on the neurobiological, clinical features and current pharmacological management of ADHD comorbid with BDs across the entire lifespan, with a major focus on the adulthood.

DISCUSSION

The pharmacology of ADHD-BD in adults is still empirical and influenced by the individual experience of the clinicians. Stimulants are endowed of a prompt efficacy and safety, whilst non-stimulants are useful when a substance abuse history is detected, although they require some weeks in order to be fully effective. In any case, an in-depth diagnostic and clinical evaluation of the single individual is mandatory.

CONCLUSION

The comorbidity of ADHD with BD is still a controversial matter, as it is the notion of adult ADHD as a distinct nosological category. Indeed, some findings highlighted the presence of common neurobiological mechanisms and overlapping clinical features, although disagreement does exist. In any case, while expecting to disentangle this crucial question, a correct management of this comorbidity is essential, which requires the co-administration of mood stabilizers. Further controlled clinical studies in large samples of adult ADHD-BD patients appear extremely urgent in order to better define possible therapeutic guidelines, as well as alternative approaches for this potentially invalidating condition.

Randomized Controlled Crossover Trials of the Pharmacokinetics of PRC-063, a Novel Multilayer Extended-Release Formulation of Methylphenidate, in Healthy Adults

PURPOSE/BACKGROUND

PRC-063 is a once-daily, extended-release oral formulation of methylphenidate hydrochloride developed to provide early and prolonged symptom improvement in patients with attention-deficit/hyperactivity disorder.

METHODS/PROCEDURES

We conducted 3 randomized, open-label crossover studies of the pharmacokinetics of PRC-063 in healthy, nonobese men and women aged 18 to 45 years. PRC-063 (100 mg/d) was compared with immediate-release methylphenidate (20 mg, 3 times daily) when administered on a single day under fasted and fed conditions and at steady state (day 5 of repeat dosing under fasted conditions). The pharmacokinetics of PRC-063 administered as capsule contents sprinkled on apple sauce, yoghurt, or ice cream were also investigated.

FINDINGS/RESULTS

PRC-063 demonstrated biphasic absorption, with 2 distinct peak plasma concentrations. Intake of a high-fat, high-calorie meal did not increase the peak plasma methylphenidate concentration (Cmax) or extent of absorption (area under the curve), however; it resulted in slower uptake versus a fasted state. During repeated dosing, steady state was reached with no further accumulation of methylphenidate from day 3. At steady state, PRC-063 gave higher evening and trough plasma methylphenidate levels than immediate-release methylphenidate (3 times daily). The pharmacokinetics of PRC-063 sprinkled on food were comparable to that of intact capsules. Reported adverse events (AEs) were consistent with the established safety profile of methylphenidate. There were no serious AEs, but 3 subjects discontinued the repeat-dosing study because of AEs assessed as possibly related to study treatment.

IMPLICATIONS/CONCLUSIONS

Our data indicate that PRC-063 can be taken with or without food or by sprinkling capsule contents on food.

Carboxylesterase 1 and Precision Pharmacotherapy: Pharmacogenetics and Nongenetic Regulators

Carboxylesterase (CES) 1 is the most abundant drug-metabolizing enzyme in human livers, comprising approximately 1% of the entire liver proteome. CES1 is responsible for 80%-95% of total hydrolytic activity in the liver and plays a crucial role in the metabolism of a wide range of drugs (especially ester-prodrugs), pesticides, environmental pollutants, and endogenous compounds. Expression and activity of CES1 vary markedly among individuals, which is a major contributing factor to interindividual variability in the pharmacokinetics (PK) and pharmacodynamics (PD) of drugs metabolized by CES1. Both genetic and nongenetic factors contribute to CES1 variability. Here, we discuss genetic polymorphisms, including single-nucleotide polymorphisms (SNPs), and copy number variants and nongenetic contributors, such as developmental status, genders, and drug-drug interactions, that could influence CES1 functionality and the PK and PD of CES1 substrates. Currently, the loss-of-function SNP G143E (rs71647871) is the only clinically significant CES1 variant identified to date, and alcohol is the only potent CES1 inhibitor that could alter the therapeutic outcomes of CES1 substrate medications. However, G143E and alcohol can only explain a small portion of the interindividual variability in the CES1 function. A better understanding of the regulation of CES1 expression and activity and identification of biomarkers for CES1 function in vivo could lead to the development of a precision pharmacotherapy strategy to improve the efficacy and safety of many CES1 substrate drugs. SIGNIFICANCE STATEMENT: The clinical relevance of CES1 has been well demonstrated in various clinical trials. Genetic and nongenetic regulators can affect CES1 expression and activity, resulting in the alteration of the metabolism and clinical outcome of CES1 substrate drugs, such as methylphenidate and clopidogrel. Predicting the hepatic CES1 function can provide clinical guidance to optimize pharmacotherapy of numerous medications metabolized by CES1.

Pharmacokinetics of methylphenidate and ritalinic acid in plasma correlations with exhaled breath and oral fluid in healthy volunteers

PURPOSE

The primary aim of this study was to explore the potential of alternative sampling matrices for methylphenidate by assessing the correlations between dl-threo-methylphenidate and dl-threo-ritalinic acid concentrations in exhaled breath and oral fluid with those in plasma, in repeated samples collected after a single oral dose of methylphenidate. The secondary aim was to study the enantioselective pharmacokinetics of methylphenidate in plasma, with a focus on interindividual variability in the metabolism of methylphenidate to ritalinic acid.

METHODS

Twelve healthy volunteers received a single oral dose of dl-threo-methylphenidate (Ritalin® capsules, 20 mg). Venous blood samples were collected for 24 h, and plasma analyzed for threo-enantiomers of methylphenidate and ritalinic acid with LC-MS/MS. Repeated sampling of exhaled breath, using a particle filter device, and of non-stimulated oral fluid, using a felt pad device, was also performed. Exhaled breath and oral fluid were analyzed with a non-enantioselective LC-MS/MS method for dl-threo-methylphenidate and dl-threo-ritalinic acid.

RESULTS

In all subjects, d-threo-methylphenidate was detectable in plasma for at least 15 h after the dose with a biphasic profile. l-threo-Methylphenidate was measurable in only five subjects and in most cases in low concentrations. However, one female subject displayed a biphasic concentration-time profile for l-threo-methylphenidate. This subject also had the highest d-threo-methylphenidate AUC (191 ng*h/mL versus 32-119 ng*h/mL in the other subjects). d-threo-Ritalinic acid concentrations were on average 25-fold higher (range 6-126) than the corresponding d-threo-methylphenidate concentrations. Single-time point plasma concentration ratios between d-threo-ritalinic acid and d-threo-methylphenidate 1.5-12 h after dose correlated highly (r = 0.88-0.98) with the d-threo-ritalinic acid AUC/d-threo-methylphenidate AUC ratio. In eleven subjects, dl-threo-methylphenidate in oral fluid mirrored the biphasic profile of methylphenidate (sum of d- and l-threo-enantiomers) in plasma, but the concentrations in oral fluid were on average 1.8 times higher than in plasma. dl-threo-Methylphenidate was detected in exhaled breath in all subjects, but there was no consistent concentration-time pattern.

CONCLUSIONS

In some subjects, the pharmacologically less active l-threo-enantiomer may contribute to the total plasma methylphenidate concentrations. Monitoring methylphenidate concentrations without enantiomeric determination carries the risk of missing such subjects, which might affect how the plasma concentrations of methylphenidate are interpreted and used for clinical decision making. The use of exhaled breath and oral fluid to assess medication adherence to MPH in patients with ADHD warrants further studies.

4-Fluoromethylphenidate: Fatal Intoxication Involving a Previously Unreported Novel Psychoactive Substance in the USA

The (±)-threo-4-fluoromethylphenidate (4F-MPH) is a fluorinated analog of the prescription central nervous system stimulant medication, methylphenidate. This novel psychoactive substance was first detected in drug paraphernalia at the Miami-Dade County Medical Examiner Department Toxicology Laboratory in 2016 but was not detected in a biological specimen until 2018. Limited literature is available on 4F-MPH, with predominate literature being published out of Europe, and no known toxicities reported in the USA. Post-mortem specimens were screened using both gas chromatography mass spectrometry and liquid chromatography ion trap mass spectrometry (LC–Ion Trap-MSn). In addition, a validated method for the quantification of 4F-MPH was developed using liquid chromatography–tandem mass spectrometry (LC–MS-MS), with a linear range of 0.01–0.500 mg/L and acceptable validation criteria including precision, bias, carry-over, linearity and endogenous/exogenous interferences. In addition to the detection of 4F-MPH, 3-methoxy-PCP, amphetamine, methamphetamine, 6-monoacetylmorphine, morphine, codeine and tetrahydrocannabinol were also identified in the decedent. A single source of blood was collected (femoral vein) and quantified in all blood tubes used for collection, with concentrations varying from 0.012 to 0.05 mg/L. Additional specimens available for screening included gastric contents and urine. An additional peak having the same targeted ions and transitions as 4F-MPH was identified in both the LC–Ion Trap-MSn screening procedure and the LC–MS-MS quantitative procedure. This peak suggests the presence of a structural isomer, possibly (±)-erythro-4-fluoromethylphenidate, which cannot be confirmed due to there being no available certified reference material. This case report presents the first time that 4F-MPH was detected in a decedent, as well as the first time 4F-MPH has been listed in the official cause of death of a decedent in Florida.

Conventional and Novel Pharmacological Approaches to Treat Dopamine-Related Disorders: Focus on Parkinson's Disease and Schizophrenia

The dopaminergic system integrated by cell groups distributed in several brain regions exerts a modulatory role in brain. Particularly important for this task are the mesencephalic dopamine neurons, which from the substantia nigra and ventral tegmental area project to the dorsal striatum and the cortical/subcortical limbic systems, respectively. Dopamine released from these neurons operates mainly via the short distance extrasynaptic volume transmission and activates five different dopaminergic receptor subtypes modulating synaptic GABA and glutamate transmission. To accomplish this task dopaminergic neurons keep mutual modulating interactions with neurons of other neurotransmitter systems, including allosteric receptor-receptor interactions in heteroreceptor complexes. As a result of its modulatory role dopaminergic mechanisms are involved in either the etiology or physiopathology of many brain diseases such as Parkinsońs disease and schizophrenia. The aim of this work is to review some novel and conventional approaches that either have been used or are currently employed to treat these diseases. Particular attention is paid to the approaches derived from the knowledge recently acquired in the realm of receptor-receptor interactions taking place through multiple dopamine heteroreceptor complexes in the plasma membrane. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Methylphenidate for attention deficit hyperactivity disorder (ADHD) in children and adolescents - assessment of adverse events in non-randomised studies

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in childhood. The psychostimulant methylphenidate is the most frequently used medication to treat it. Several studies have investigated the benefits of methylphenidate, showing possible favourable effects on ADHD symptoms, but the true magnitude of the effect is unknown. Concerning adverse events associated with the treatment, our systematic review of randomised clinical trials (RCTs) demonstrated no increase in serious adverse events, but a high proportion of participants suffered a range of non-serious adverse events.

OBJECTIVES

To assess the adverse events associated with methylphenidate treatment for children and adolescents with ADHD in non-randomised studies.

SEARCH METHODS

In January 2016, we searched CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, 12 other databases and two trials registers. We also checked reference lists and contacted authors and pharmaceutical companies to identify additional studies.

SELECTION CRITERIA

We included non-randomised study designs. These comprised comparative and non-comparative cohort studies, patient-control studies, patient reports/series and cross-sectional studies of methylphenidate administered at any dosage or formulation. We also included methylphenidate groups from RCTs assessing methylphenidate versus other interventions for ADHD as well as data from follow-up periods in RCTs. Participants had to have an ADHD diagnosis (from the 3rd to the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders or the 9th or 10th edition of theInternational Classification of Diseases, with or without comorbid diagnoses. We required that at least 75% of participants had a normal intellectual capacity (intelligence quotient of more than 70 points) and were aged below 20 years. We excluded studies that used another ADHD drug as a co-intervention.

DATA COLLECTION AND ANALYSIS

Fourteen review authors selected studies independently. Two review authors assessed risk of bias independently using the ROBINS-I tool for assessing risk of bias in non-randomised studies of interventions. All review authors extracted data. We defined serious adverse events according to the International Committee of Harmonization as any lethal, life-threatening or life-changing event. We considered all other adverse events to be non-serious adverse events and conducted meta-analyses of data from comparative studies. We calculated meta-analytic estimates of prevalence from non-comparative cohorts studies and synthesised data from patient reports/series qualitatively. We investigated heterogeneity by conducting subgroup analyses, and we also conducted sensitivity analyses.

MAIN RESULTS

We included a total of 260 studies: 7 comparative cohort studies, 6 of which compared 968 patients who were exposed to methylphenidate to 166 controls, and 1 which assessed 1224 patients that were exposed or not exposed to methylphenidate during different time periods; 4 patient-control studies (53,192 exposed to methylphenidate and 19,906 controls); 177 non-comparative cohort studies (2,207,751 participants); 2 cross-sectional studies (96 participants) and 70 patient reports/series (206 participants). Participants' ages ranged from 3 years to 20 years. Risk of bias in the included comparative studies ranged from moderate to critical, with most studies showing critical risk of bias. We evaluated all non-comparative studies at critical risk of bias. The GRADE quality rating of the evidence was very low.Primary outcomesIn the comparative studies, methylphenidate increased the risk ratio (RR) of serious adverse events (RR 1.36, 95% confidence interval (CI) 1.17 to 1.57; 2 studies, 72,005 participants); any psychotic disorder (RR 1.36, 95% CI 1.17 to 1.57; 1 study, 71,771 participants); and arrhythmia (RR 1.61, 95% CI 1.48 to 1.74; 1 study, 1224 participants) compared to no intervention.In the non-comparative cohort studies, the proportion of participants on methylphenidate experiencing any serious adverse event was 1.20% (95% CI 0.70% to 2.00%; 50 studies, 162,422 participants). Withdrawal from methylphenidate due to any serious adverse events occurred in 1.20% (95% CI 0.60% to 2.30%; 7 studies, 1173 participants) and adverse events of unknown severity led to withdrawal in 7.30% of participants (95% CI 5.30% to 10.0%; 22 studies, 3708 participants).Secondary outcomesIn the comparative studies, methylphenidate, compared to no intervention, increased the RR of insomnia and sleep problems (RR 2.58, 95% CI 1.24 to 5.34; 3 studies, 425 participants) and decreased appetite (RR 15.06, 95% CI 2.12 to 106.83; 1 study, 335 participants).With non-comparative cohort studies, the proportion of participants on methylphenidate with any non-serious adverse events was 51.2% (95% CI 41.2% to 61.1%; 49 studies, 13,978 participants). These included difficulty falling asleep, 17.9% (95% CI 14.7% to 21.6%; 82 studies, 11,507 participants); headache, 14.4% (95% CI 11.3% to 18.3%; 90 studies, 13,469 participants); abdominal pain, 10.7% (95% CI 8.60% to 13.3%; 79 studies, 11,750 participants); and decreased appetite, 31.1% (95% CI 26.5% to 36.2%; 84 studies, 11,594 participants). Withdrawal of methylphenidate due to non-serious adverse events occurred in 6.20% (95% CI 4.80% to 7.90%; 37 studies, 7142 participants), and 16.2% were withdrawn for unknown reasons (95% CI 13.0% to 19.9%; 57 studies, 8340 participants).

AUTHORS' CONCLUSIONS

Our findings suggest that methylphenidate may be associated with a number of serious adverse events as well as a large number of non-serious adverse events in children and adolescents, which often lead to withdrawal of methylphenidate. Our certainty in the evidence is very low, and accordingly, it is not possible to accurately estimate the actual risk of adverse events. It might be higher than reported here.Given the possible association between methylphenidate and the adverse events identified, it may be important to identify people who are most susceptible to adverse events. To do this we must undertake large-scale, high-quality RCTs, along with studies aimed at identifying responders and non-responders.

Potential for Dependence on Lisdexamfetamine - In vivo and In vitro Aspects

Although lisdexamfetamine is used as a recreational drug, little research exists regarding its potential for dependence or its precise mechanisms of action. This study aims to evaluate the psychoactivity and dependence profile of lisdexamfetamine using conditioned place preference and self-administration paradigms in rodents. Additionally, biochemical techniques are used to assess alterations in the dopamine levels in striatal synaptosomes following administration of lisdexamfetamine. Lisdexamfetamine increased both conditioned place preference and self-administration. Moreover, after administration of the lisdexamfetamine, dopamine levels in the striatal synaptosomes were significantly increased. Although some modifications should be made to the analytical methods, performing high performance liquid chromatography studies on synaptosomes can aid in predicting dependence liability when studying new psychoactive substances in the future. Collectively, lisdexamfetamine has potential for dependence possible via dopaminergic pathway.

The impact of methylphenidate and its enantiomers on dopamine synthesis and metabolism in vitro

Methylphenidate (MPH), a psychostimulant, is an effective first-line treatment for the symptoms associated with Attention-Deficit/Hyperactivity Disorder (ADHD). Although most MPH formulations are composed of the racemic 1:1 mixture of the two enantiomers (d- and l-threo), converging lines of evidence indicate that d-threo MPH seems to be superior to the l-isomer. We aimed to investigate whether MPH racemic mixture or pure enantiomers influence the enzyme activity of tyrosine hydroxylase (TH), monoamine oxidase B (MAO-B), catechol-O-methyltransferase (COMT), and aldehyde dehydrogenase (ALDH) in vitro in homogenates of rat PC12 cells incubated with racemic, d- and l-threo MPH (1nM up to 100μM), or a vehicle for control. We could observe dose dependent enhancement of TH activity with d-threo MPH, probably due to its higher affinity to the enzyme, which we could confirm for d-threo versus l-threo MPH via docking and molecular dynamic simulations analysis. MAO-B enzyme activity was found to be enhanced when incubated with both d- and l-isomers but not with the racemic mixture. This conflicting result was hypothesized to be due to possible aggregation of the two enantiomers or other molecular conformations. Such a possible interaction was observed indirectly, when TH was incubated with constant d-threo MPH while increasing l-isomer (increasing total MPH concentrations). Hence, TH activity was slightly decreased with increased l-isomer. In conclusion, the current in vitro investigation points to the stereoselectivity of the investigated enzymes and pharmacological effects of MPH enantiomers.

Metabolic Patterns of Fentanyl, Meperidine, Methylphenidate, Tapentadol and Tramadol Observed in Urine, Serum or Plasma

Drug testing is a useful tool to identify drug use or monitor adherence to prescription drugs. The interpretation of drug results can be complicated based on the pattern and proportional concentrations of drugs and/or drug metabolite(s). The purpose of this retrospective study was to detect the positivity rates and metabolic patterns of five prescription drugs, including fentanyl, meperidine, methylphenidate, tapentadol and tramadol. Retrospective data were retrieved from the laboratory information system in a national reference laboratory. Drug testing was performed using four mass spectrometry methods that were validated for clinical use. For urine specimens, the positivity rate was the highest for methylphenidate (62.3%, n = 2,489), followed by tramadol (43.7%, n = 3,483), fentanyl (41.9%, n = 4,657), tapentadol (37.9%, n = 736) and meperidine (8.3%, n = 138). Among positive samples, both parent drug and metabolite(s) was detectable in 94.9% of meperidine samples, 94.5% of tramadol samples, 93.8% of fentanyl samples, 89.9% of methylphenidate and 86.6% of tapentadol samples. For serum or plasma specimens, the positivity rate was the highest for tapentadol (75.0%, n = 39), followed by methylphenidate (74.2%, n = 569), fentanyl (53.6%, n = 113), meperidine (41.9%, n = 18) and tramadol (28.9%, n = 213). Similar metabolic patterns were found in serum or plasma. Of positive results, both parent drug and metabolite(s) were found in 94.7% of fentanyl samples, 83.3% of meperidine samples, 79.6% of methylphenidate samples, 53.8% of tapentadol samples and 44.1% of tramadol samples. Our data demonstrates the metabolic patterns of five drugs from a random urine or serum/plasma collection in patients that have been prescribed these medications. The data presented can be used to guide clinicians in determining drug adherence by assessing the positivity rates of the parent drug and corresponding metabolite(s).

Methylphenidate attenuates the response to cold pain but not to aversive auditory stimuli in healthy human: a double-blind randomized controlled study

This double-blind, crossover, randomized placebo-controlled study found that methylphenidate has a specific effect on nociceptive pathways rather than a generalized effect on aversive sensory modalities.

Introduction:

We recently showed that the psycho-stimulant norepinephrine–dopamine reuptake inhibitor methylphenidate (MP) prolonged cold pain threshold and tolerance in adults with attention-deficit hyperactivity disorder (ADHD).

Objectives:

The objectives of the present study were to: (1) examine whether MP has antinociceptive properties in healthy men; (2) test MP's effects on responses to aversive auditory stimuli. The underlying aim was to determine whether MP exerts antinociceptive properties or more generalized, nonspecific attenuating effects on different aversive sensory modalities.

Methods:

This double-blind, crossover, randomized placebo-controlled study consisted of 2 sessions one week apart from each other. In each session, pain threshold (seconds) and tolerance (seconds) in response to painful cold stimulation were measured. Additionally, threshold (dB) and tolerance (seconds) to loud aversive auditory stimuli (500 Hz, 2000 Hz and white noise) were also tested prior to and 2 hours following the administration of a single dose of either 20 mg MP or an identical looking placebo.

Results:

Forty men, 26.1 ± 4.0 (mean ± SD) years were enrolled in the study. Wilcoxon signed-rank test analyses showed that MP, but not the placebo, produced a significant increase in cold pain threshold (from 4.1 ± 2.6 to 5.4 ± 3.1 seconds, P = 0.001 and from 4.5 ± 2.6 to 4.3 ± 2.7 seconds, P = 0.2, respectively) and tolerance (from 57.8 ± 54.0 to 73.8 ± 61.8 seconds, P = 0.001 and from 52.5 ± 53.7 sec to 57.0 ± 52.9 seconds, P = 0.1, respectively). No significant changes were found in any of the auditory parameters.

Conclusion:

These results suggest that MP has an effect on nociceptive pathways rather than a nonspecific, generalized attenuating effect on aversive sensory stimuli.

Methylphenidate effects in the young brain: friend or foe?

Attention deficit hyperactivity disorder (ADHD) is one of the most prevalent neuropsychiatry disorders in children and adolescents, and methylphenidate (MPH) is a first-line stimulant drug available worldwide for its treatment. Despite the proven therapeutic efficacy, concerns have been raised regarding the possible consequences of chronic MPH exposure during childhood and adolescence. Disturbances in the neurodevelopment at these crucial stages are major concerns given the unknown future life consequences. This review is focused on the long-term adverse effects of MPH to the brain biochemistry. Reports conducted with young and/or adolescent animals and studies with humans are reviewed in the context of long-term consequences after early life-exposure. MPH pharmacokinetics is also reviewed as there are differences among laboratory animals and humans that may be relevant to extrapolate the findings. Studies reveal that exposure to MPH in laboratory animals during young and/or adolescent ages can impact the brain, but the outcomes are dependent on MPH dose, treatment period, and animal's age. Importantly, the female sex is largely overlooked in both animal and human studies. Unfortunately, human reports that evaluate adults following adolescent or child exposure to MPH are very scarce. In general, human data indicates that MPH is generally safe, although it can promote several brain changes in early ages. Even so, there is a lack of long course patient evaluation to clearly establish whether MPH-induced changes are friendly or foe to the brain and more human studies are needed to assess the adult brain changes that arise from early MPH treatment.

Analytical characterization and pharmacological evaluation of the new psychoactive substance 4-fluoromethylphenidate (4F-MPH) and differentiation between the (±)-threo and (±)-erythro diastereomers

Misuse of (±)-threo-methylphenidate (methyl-2-phenyl-2-(piperidin-2-yl)acetate; Ritalin®; MPH) has long been acknowledged, but the appearance of MPH analogs in the form of 'research chemicals' has only emerged in more recent years. 4-Fluoromethylphenidate (4F-MPH) is one of these recent examples. This study presents the identification and analytical characterization of two powdered 4F-MPH products that were obtained from an online vendor in 2015. Interestingly, the products appeared to have originated from two distinct batches given that one product consisted of (±)-threo-4F-MPH isomers whereas the second sample consisted of a mixture of (±)-threo and (±)-erythro 4F-MPH. Monoamine transporter studies using rat brain synaptosomes revealed that the biological activity of the 4F-MPH mixture resided with the (±)-threo and not the (±)-erythro isomers based on higher potencies determined for blockage of dopamine uptake (IC₅₀ 4F-MPH_mixture  = 66 nM vs. IC₅₀ (±)-threo = 61 nM vs. IC₅₀ (±)-erythro = 8,528 nM) and norepinephrine uptake (IC₅₀ 4F-MPH_mixture  = 45 nM vs. (±)-threo = 31 nM vs. IC₅₀ (±)-erythro = 3,779 nM). In comparison, MPH was three times less potent than (±)-threo-4F-MPH at the dopamine transporter (IC₅₀  = 131 nM) and around 2.5 times less potent at the norepinephrine transporter (IC₅₀  = 83 nM). Both substances were catecholamine selective with IC₅₀ values of 8,805 nM and >10,000 nM for (±)-threo-4F-MPH and MPH at the serotonin transporter. These findings suggest that the psychostimulant properties of (±)-threo-4F-MPH might be more potent in humans than MPH. Copyright © 2017 John Wiley & Sons, Ltd.

Effectiveness of atomoxetine and methylphenidate for problematic online gaming in adolescents with attention deficit hyperactivity disorder

OBJECTIVE

There is a high prevalence of problematic online gaming in adolescents with attention deficit hyperactivity disorder (ADHD). In the current study, we compared the effectiveness of atomoxetine (ATM) and methylphenidate (MPH) on problematic online gaming in adolescents with ADHD.

METHODS

We recruited 86 adolescents diagnosed with ADHD together with Internet gaming disorder. These participants were divided into two treatment groups: 44 participants were treated with MPH for 12 weeks, and 42 participants were treated with ATM for 12 weeks.

RESULTS

During the 3-month study period, the MPH group showed greater improvement in Korean ADHD rating scale scores than the ATM group. The ATM group showed greater improvement in Child Depression Inventory scores than the MPH group. However, Young Internet Addiction Scale and Behavioral Inhibition & Activation Scales score changes did not differ significantly between the MPH and ATM groups. In both groups, changes in Young Internet Addiction Scale scores were positively correlated with the changes in Behavioral Inhibition & Activation Scales scores.

CONCLUSIONS

Both MPH and ATM reduced the severity of Internet gaming disorder symptoms, and this reduction was correlated with impulsivity reduction, which also resulted from both ADHD medications. These findings suggest impulsivity plays a critical role in the development of problematic online gaming.

From Clinical Application to Cognitive Enhancement: The Example of Methylphenidate

Methylphenidate (MPD) is a central nervous system (CNS) stimulant, which belongs to the phenethylamine group and is mainly used in the treatment of attention deficit hyperactive disorder (ADHD). However, a growing number of young individuals misuse or abuse MPD to sustain attention, enhance intellectual capacity and increase memory. Recently, the use of MPD as a cognitive enhancement substance has received much attention and raised concerns in the literature and academic circles worldwide. The prescribing frequency of the drug has increased sharply as consequence of the more accurate diagnosis of the ADHD and the popularity of the drug itself due to its beneficial short-term effect. However, careful monitoring is required, because of possible abuse. In this review different aspects concerning the use of MPD have been approached. Data showing its abuse among college students are given, when the drug is prescribed short term beneficial effects and side effects are provided; moreover studies on animal-models suggesting long lasting negative effects on healthy brains are discussed. Finally, emphasis is given to the available formulations and pharmacology.

A Single-Dose, Single-Period Pharmacokinetic Assessment of an Extended-Release Orally Disintegrating Tablet of Methylphenidate in Children and Adolescents with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

To determine the pharmacokinetic (PK) profile of a proprietary formulation of methylphenidate (MPH) in children and adolescents with attention-deficit/hyperactivity disorder (ADHD) in a phase 1 study. Methylphenidate extended-release orally disintegrating tablets (MPH XR-ODTs) combine two technologies in a single-tablet formulation-an extended-release profile that was designed for once-daily dosing in an ODT that does not require water or chewing for ingestion.

METHODS

This was a single-dose, open-label, single-period, single-treatment study, in which 32 children with ADHD who were receiving MPH in doses of 40 or 60 mg before beginning the study each received a 60-mg dose (2 × 30 mg) of MPH XR-ODT. The following plasma PK parameters of MPH were determined for participants grouped by age (6-7, 8-9, 10-12, and 13-17 years old): maximum concentration (Cmax), time to maximum concentration (Tmax), elimination half-life (T½), area under the curve from 0 hours to infinity (AUCinf), oral clearance (CL/F), and volume of distribution in the terminal phase (Vz/F). Safety and tolerability were also assessed.

RESULTS

A total of 32 participants received the study drug. For all participants, plasma concentration-time profiles of MPH exhibited a broad peak after administration of MPH XR-ODT through ∼8 hours, indicating extended release from the formulation, followed by an apparent first-order elimination phase. As age increased, MPH exposure decreased and mean estimates of CL/F increased; however, weight-normalized CL/F values were comparable across age groups. Similarly, mean estimates of Vz/F increased with age, but weight-normalization decreased differences across age groups, with the exception of the youngest age group, which had higher values. All adverse events (AEs) were mild.

CONCLUSION

This XR-ODT formulation of MPH demonstrated weight-normalized clearance rates that were consistent across all age groups, a PK profile consistent with once-daily dosing, and an AE profile consistent with this class of medication in children and adolescents with ADHD.

Smart drugs and synthetic androgens for cognitive and physical enhancement: revolving doors of cosmetic neurology

Cognitive enhancement can be defined as the use of drugs and/or other means with the aim to improve the cognitive functions of healthy subjects in particular memory, attention, creativity and intelligence in the absence of any medical indication. Currently, it represents one of the most debated topics in the neuroscience community. Human beings always wanted to use substances to improve their cognitive functions, from the use of hallucinogens in ancient civilizations in an attempt to allow them to better communicate with their gods, to the widespread use of caffeine under various forms (energy drinks, tablets, etc.), to the more recent development of drugs such as stimulants and glutamate activators. In the last ten years, increasing attention has been given to the use of cognitive enhancers, but up to now there is still only a limited amount of information concerning the use, effect and functioning of cognitive enhancement in daily life on healthy subjects. The first aim of this paper was to review current trends in the misuse of smart drugs (also known as Nootropics) presently available on the market focusing in detail on methylphenidate, trying to evaluate the potential risk in healthy individuals, especially teenagers and young adults. Moreover, the authors have explored the issue of cognitive enhancement compared to the use of Anabolic Androgenic Steroids (AAS) in sports. Finally, a brief overview of the ethical considerations surrounding human enhancement has been examined.

Methylphenidate for children and adolescents with attention deficit hyperactivity disorder (ADHD)

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is one of the most commonly diagnosed and treated psychiatric disorders in childhood. Typically, children with ADHD find it difficult to pay attention, they are hyperactive and impulsive.Methylphenidate is the drug most often prescribed to treat children and adolescents with ADHD but, despite its widespread use, this is the first comprehensive systematic review of its benefits and harms.

OBJECTIVES

To assess the beneficial and harmful effects of methylphenidate for children and adolescents with ADHD.

SEARCH METHODS

In February 2015 we searched six databases (CENTRAL, Ovid MEDLINE, EMBASE, CINAHL, PsycINFO, Conference Proceedings Citations Index), and two trials registers. We checked for additional trials in the reference lists of relevant reviews and included trials. We contacted the pharmaceutical companies that manufacture methylphenidate to request published and unpublished data.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing methylphenidate versus placebo or no intervention in children and adolescents aged 18 years and younger with a diagnosis of ADHD. At least 75% of participants needed to have an intellectual quotient of at least 70 (i.e. normal intellectual functioning). Outcomes assessed included ADHD symptoms, serious adverse events, non-serious adverse events, general behaviour and quality of life.

DATA COLLECTION AND ANALYSIS

Seventeen review authors participated in data extraction and risk of bias assessment, and two review authors independently performed all tasks. We used standard methodological procedures expected within Cochrane. Data from parallel-group trials and first period data from cross-over trials formed the basis of our primary analyses; separate analyses were undertaken using post-cross-over data from cross-over trials. We used Trial Sequential Analyses to control for type I (5%) and type II (20%) errors, and we assessed and downgraded evidence according to the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) approach for high risk of bias, imprecision, indirectness, heterogeneity and publication bias.

MAIN RESULTS

The studies.We included 38 parallel-group trials (5111 participants randomised) and 147 cross-over trials (7134 participants randomised). Participants included individuals of both sexes, at a boys-to-girls ratio of 5:1, and participants' ages ranged from 3 to 18 years across most studies (in two studies ages ranged from 3 to 21 years). The average age across all studies was 9.7 years. Most participants were from high-income countries.The duration of methylphenidate treatment ranged from 1 to 425 days, with an average duration of 75 days. Methylphenidate was compared to placebo (175 trials) or no intervention (10 trials). Risk of Bias.All 185 trials were assessed to be at high risk of bias. Primary outcomes. Methylphenidate may improve teacher-rated ADHD symptoms (standardised mean difference (SMD) -0.77, 95% confidence interval (CI) -0.90 to -0.64; 19 trials, 1698 participants; very low-quality evidence). This corresponds to a mean difference (MD) of -9.6 points (95% CI -13.75 to -6.38) on the ADHD Rating Scale (ADHD-RS; range 0 to 72 points; DuPaul 1991a). A change of 6.6 points on the ADHD-RS is considered clinically to represent the minimal relevant difference. There was no evidence that methylphenidate was associated with an increase in serious (e.g. life threatening) adverse events (risk ratio (RR) 0.98, 95% CI 0.44 to 2.22; 9 trials, 1532 participants; very low-quality evidence). The Trial Sequential Analysis-adjusted intervention effect was RR 0.91 (CI 0.02 to 33.2).

SECONDARY OUTCOMES

Among those prescribed methylphenidate, 526 per 1000 (range 448 to 615) experienced non-serious adverse events, compared with 408 per 1000 in the control group. This equates to a 29% increase in the overall risk of any non-serious adverse events (RR 1.29, 95% CI 1.10 to 1.51; 21 trials, 3132 participants; very low-quality evidence). The Trial Sequential Analysis-adjusted intervention effect was RR 1.29 (CI 1.06 to 1.56). The most common non-serious adverse events were sleep problems and decreased appetite. Children in the methylphenidate group were at 60% greater risk for trouble sleeping/sleep problems (RR 1.60, 95% CI 1.15 to 2.23; 13 trials, 2416 participants), and 266% greater risk for decreased appetite (RR 3.66, 95% CI 2.56 to 5.23; 16 trials, 2962 participants) than children in the control group.Teacher-rated general behaviour seemed to improve with methylphenidate (SMD -0.87, 95% CI -1.04 to -0.71; 5 trials, 668 participants; very low-quality evidence).A change of seven points on the Child Health Questionnaire (CHQ; range 0 to 100 points; Landgraf 1998) has been deemed a minimal clinically relevant difference. The change reported in a meta-analysis of three trials corresponds to a MD of 8.0 points (95% CI 5.49 to 10.46) on the CHQ, which suggests that methylphenidate may improve parent-reported quality of life (SMD 0.61, 95% CI 0.42 to 0.80; 3 trials, 514 participants; very low-quality evidence).

AUTHORS' CONCLUSIONS

The results of meta-analyses suggest that methylphenidate may improve teacher-reported ADHD symptoms, teacher-reported general behaviour, and parent-reported quality of life among children and adolescents diagnosed with ADHD. However, the low quality of the underpinning evidence means that we cannot be certain of the magnitude of the effects. Within the short follow-up periods typical of the included trials, there is some evidence that methylphenidate is associated with increased risk of non-serious adverse events, such as sleep problems and decreased appetite, but no evidence that it increases risk of serious adverse events.Better designed trials are needed to assess the benefits of methylphenidate. Given the frequency of non-serious adverse events associated with methylphenidate, the particular difficulties for blinding of participants and outcome assessors point to the advantage of large, 'nocebo tablet' controlled trials. These use a placebo-like substance that causes adverse events in the control arm that are comparable to those associated with methylphenidate. However, for ethical reasons, such trials should first be conducted with adults, who can give their informed consent.Future trials should publish depersonalised individual participant data and report all outcomes, including adverse events. This will enable researchers conducting systematic reviews to assess differences between intervention effects according to age, sex, comorbidity, type of ADHD and dose. Finally, the findings highlight the urgent need for large RCTs of non-pharmacological treatments.

Assessment of potential cardiovascular risks of methylphenidate in comparison with sibutramine: do we need a SCOUT (trial)?

With the recent approval of methylphenidate (MPH) for treating attention-deficit/hyperactivity disorder (ADHD) in adults, the number of patients exposed will increase tremendously. The ongoing debate on the cardiovascular safety of MPH has triggered two large retrospective cohort studies in children and adolescents as well as in young to middle-aged adults. These studies looked into serious cardiovascular events (sudden cardiac death, acute myocardial infarction and stroke) as primary endpoints and concluded that MPH was safe after a mean duration of 2.1 years of follow-up in children and adolescents and mean duration of 0.33 years of current use in adults. The results are encouraging with respect to the short- and medium-term use of MPH. Without the inherent limitations of retrospective cohort studies, a prospective randomized, double-blind, placebo-controlled, multicenter trial in individuals stratified for cardiovascular risk factors would allow for an optimized risk assessment. With many millions of patients treated per year and drawing parallels to the lately discovered risks of sibutramine, another sympathomimetic with an overlapping mode of action and similar side effects on heart rate and blood pressure, we hypothesize that such a trial might be a dedicated risk mitigation strategy for public health. A critical assessment of cardiovascular side effects of MPH appears particularly warranted, because ADHD is associated with obesity, smoking and poor health in general. We summarize recent findings with the focus on cardiovascular risks of MPH in humans; we additionally analyze the limited number of rodent studies that have addressed cardiovascular risks of MPH.

The spectroscopic (FT-IR, FT-Raman, (l3)C, (1)H NMR and UV) and NBO analyses of 4-bromo-1-(ethoxycarbonyl)piperidine-4-carboxylic acid

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 4-bromo-1-(ethoxycarbonyl)piperidine-4-carboxylic acid (BEPA). BEPA has been characterized by FT-IR, FT-Raman, (1)H NMR, (13)C NMR and UV spectroscopy. The FT-IR and FT-Raman spectra of BEPA were recorded in the solid phase. The optimized geometry was calculated by B3LYP and M06-2X methods using 6-311G(d,p) basis set. The FT-IR and FT-Raman spectra of BEPA were calculated at the same level and were interpreted in terms of Potential Energy Distribution (PED) analysis. The scaled theoretical wavenumber showed very good agreement with the experimental values. The (1)H and (l3)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge-Independent Atomic Orbital (GIAO) method. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using Natural Bond Orbital (NBO) analysis. Density plots over the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) energy surface directly identifies the donor and acceptor atoms in the molecule. It also provides information about the charge transfer within the molecule. To obtain chemical reactivity of the molecule, the molecular electrostatic potential (MEP) surface map is plotted over the optimized geometry of the molecule.

Comparative efficacy, acceptability, and tolerability of dexmethylphenidate versus placebo in child and adolescent ADHD: a meta-analysis of randomized controlled trials

BACKGROUND

The efficacy of dexmethylphenidate (d-MPH) has been proven in the treatment of children and adolescents with attention-deficit hyperactivity disorder (ADHD).

OBJECTIVE

The aim of this systematic review is to determine the efficacy, acceptability, and tolerability of d-MPH in child and adolescent ADHD.

METHODS

The searches of SCOPUS, MEDLINE, CINAHL, and Cochrane Controlled Trials Register were performed in February 2015. All randomized controlled trials of d-MPH versus placebo that were performed in children and adolescents with ADHD up to 18 years of age were included in the study. The efficacy was measured by using the pooled mean-endpoint or mean-changed scores of ADHD rating scales and the response rate. Acceptability and tolerability were measured by using the pooled rates of overall discontinuation and discontinuation due to adverse events, respectively.

RESULTS

A total of 1,124 children and adolescents diagnosed as having ADHD were included in this review. In a laboratory school setting, the pooled mean-change and mean-endpoint scores in the d-MPH-treated group were significantly greater than those of the placebo-treated group with standardized mean difference (95% confidence interval [CI]) of -1.20 (-1.73, -0.67), I (2)=95%. Additionally, the pooled mean-changed scores of the ADHD rating scales for teachers and parents in the d-MPH-treated group were significantly greater than that of the placebo-treated group with weighted mean difference (95% CI) of -13.01 (-15.97, -10.05), I (2)=0% and (95% CI) of -12.99 (-15.57, -10.42), I (2)=0%, respectively. The pooled response rate in the d-MPH-treated groups had a significance higher than that of the placebo-treated group. The rates of pooled overall discontinuation and discontinuation due to adverse events between the two groups were not significantly different.

CONCLUSION

Based on the findings in this review, it can be concluded that d-MPH medication is efficacious and tolerable in child and adolescent ADHD. However, the acceptability of d-MPH is no greater than that of the placebo. Further systematic studies may confirm these findings.

Dopamine reuptake transporter (DAT) "inverse agonism"--a novel hypothesis to explain the enigmatic pharmacology of cocaine

The long held view is cocaine's pharmacological effects are mediated by monoamine reuptake inhibition. However, drugs with rapid brain penetration like sibutramine, bupropion, mazindol and tesofensine, which are equal to or more potent than cocaine as dopamine reuptake inhibitors, produce no discernable subjective effects such as drug "highs" or euphoria in drug-experienced human volunteers. Moreover they are dysphoric and aversive when given at high doses. In vivo experiments in animals demonstrate that cocaine's monoaminergic pharmacology is profoundly different from that of other prescribed monoamine reuptake inhibitors, with the exception of methylphenidate. These findings led us to conclude that the highly unusual stimulant profile of cocaine and related compounds, eg methylphenidate, is not mediated by monoamine reuptake inhibition alone. We describe the experimental findings which suggest cocaine serves as a negative allosteric modulator to alter the function of the dopamine reuptake transporter (DAT) and reverse its direction of transport. This results in a firing-dependent, retro-transport of dopamine into the synaptic cleft. The proposed mechanism of cocaine is, therefore, different from other small molecule negative allostereric modulators of the monoamine reuptake transporters, eg SoRI-6238, which merely reduce the rate of inward transport. Because the physiological role of DAT is to remove dopamine from the synapse and the action of cocaine is the opposite of this, we have postulated that cocaine's effect is analogous to an inverse agonist. If this hypothesis is validated then cocaine is the prototypical compound that exemplifies a new class of monoaminergic drugs; DAT "inverse agonists". This article is part of the Special Issue entitled 'CNS Stimulants'.

Evidence-based guidelines for the pharmacological management of attention deficit hyperactivity disorder: update on recommendations from the British Association for Psychopharmacology

Attention deficit hyperactivity disorder (ADHD) is a common condition with a high societal burden. The present guidelines summarise current literature, generating expert consensus recommendations for the treatment of ADHD in children and adults. These guidelines also provide a review of recent research in the fields of neuroimaging, neuropsychology and genetics of ADHD. Novel discoveries in these areas have informed physiological models for the disease. Since the publication of the previous British Association for Psychopharmacology guidelines in 2008, new drugs have been licensed and further compounds are being investigated. The publication of randomised controlled trials of psychological interventions has contributed to the range of treatment options for ADHD. As the disorder has been diagnosed more frequently there has been greater focus on comorbid conditions and how they impact treatment. Services have continued to develop for the treatment of ADHD in adults and care agreements have been introduced to facilitate access to treatment.

Differences in the neurochemical and behavioural profiles of lisdexamfetamine methylphenidate and modafinil revealed by simultaneous dual-probe microdialysis and locomotor activity measurements in freely-moving rats

Lisdexamfetamine dimesylate is a novel prodrug approved in North America, Europe and Brazil for treating attention deficit hyperactivity disorder (ADHD). It undergoes rate-limited hydrolysis by red blood cells to yield d-amphetamine. Following our previous work comparing lisdexamfetamine with d-amphetamine, the neurochemical and behavioural profiles of lisdexamfetamine, methylphenidate and modafinil were compared by dual-probe microdialysis in the prefrontal cortex (PFC) and striatum of conscious rats with simultaneous locomotor activity measurement. We employed pharmacologically equivalent doses of all compounds and those that spanned the therapeutically relevant and psychostimulant range. Lisdexamfetamine (0.5, 1.5, 4.5 mg/kg d-amphetamine base, per os (po)), methylphenidate (3, 10, 30 mg/kg base, po) and modafinil (100, 300, 600 mg/kg base, po) increased efflux of dopamine and noradrenaline in PFC, and dopamine in striatum. Only lisdexamfetamine increased 5-hydroxytryptamine (5-HT) efflux in PFC and striatum. Lisdexamfetamine had larger and more sustained effects on catecholaminergic neurotransmission than methylphenidate or modafinil. Linear correlations were observed between striatal dopamine efflux and locomotor activity for lisdexamfetamine and methylphenidate, but not modafinil. Regression slopes revealed greater increases in extracellular dopamine could be elicited without producing locomotor activation by lisdexamfetamine than methylphenidate. These results are consistent with clinical findings showing that lisdexamfetamine is an effective ADHD medication with prolonged duration of action and good separation between its therapeutic actions and stimulant side-effects.

Methylphenidate and impulsivity: a comparison of effects of methylphenidate enantiomers on delay discounting in rats

RATIONALE

Current formulations of methylphenidate (MPH) used in treatment of attention-deficit/hyperactivity disorder (ADHD) result in significantly different bioavailability of MPH enantiomers. Daytrana®, a dl-MPH transdermal patch system, produces higher levels of l-MPH than when dl-MPH is administered orally (e.g., Ritalin®). One potential limitation of increased l-MPH was indicated in a preclinical study showing l-MPH may attenuate effects of d-MPH.

OBJECTIVES

The objective of the study was to investigate the interactive effects of MPH enantiomers by (1) assessing drug effects via a preclinical model of "impulsivity" and (2) performing a quantitative dose equivalence analysis of MPH enantiomer interactions.

METHODS

Sprague-Dawley rats were trained to emit either of two responses, one producing an immediate food pellet, the other producing four pellets delivered at increasing delays (0, 8, and 32 s). The percent selection of the larger food amount was graphed as a function of delay with the area under the curve (AUC) assessed. Increases in AUC are consistent with decreases in "impulsivity" (i.e., selection of the smaller, immediate over the larger, delayed reinforcer).

RESULTS

Systemic administration of dl-MPH and d-MPH dose-dependently increased AUC, while l-MPH, morphine, and pentobarbital did not alter AUC. An analysis based upon dose equivalence indicated that dl-MPH produced additive effects that were not different from that predicted from effects of the enantiomers administered alone.

CONCLUSIONS

The present results indicate pharmacologically selective effects in that only drugs prescribed for the treatment of ADHD symptoms decreased a measure of "impulsivity" and that l-MPH likely does not attenuate or enhance the effects of d-MPH in the current delay-discounting task.