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1.  Attention-deficit hyperactivity disorder (ADHD) stimulant medications as cognitive enhancers 
Recent increases in attention deficit hyperactivity disorder (ADHD) diagnoses, and the escalation of stimulant prescriptions, has raised concern about diversion and abuse of stimulants, as well as the ethics of using these drugs as “cognitive enhancers.”Such concern appears misplaced in the face of substantial evidence that stimulant drugs do not improve the academic performance of ADHD-diagnosed students. Moreover, numerous studies have found little or no benefit of stimulants on neuropsychological tests of ADHD-diagnosed as well as normal, individuals. This paper examines the apparent paradox: why don't drugs that improve “attention,” produce better academic outcomes in ADHD-diagnosed students? We found that stimulant drugs significantly improved impairment of episodic memory in ADHD-diagnosed undergraduate students. Nevertheless, we also found consistent academic deficits between ADHD students and their non-ADHD counterparts, regardless of whether or not they used stimulant medications. We reviewed the current literature on the behavioral effects of stimulants, to try to find an explanation for these conflicting phenomena. Across a variety of behavioral tasks, stimulants have been shown to reduce emotional reactions to frustration, improve the ability to detect errors, and increase effortful behavior. However, all of these effects would presumably enhance academic performance. On the other hand, the drugs were also found to promote “risky behavior” and to increase susceptibility to environmental distraction. Such negative effects, including the use of drugs to promote wakefulness for last minute study, might explain the lack of academic benefit in the “real world,” despite their cognitive potential. Like many drugs, stimulants influence behavior in multiple ways, depending on the environmental contingencies. Depending on the circumstances, stimulants may, or may not, enhance cognition.
PMCID: PMC3666055  PMID: 23754970
attention-deficit hyperactivity disorder; cognitive enhancement; episodic memory; stimulants; amphetamine; methylphenidate
2.  Misuse of Prescribed Stimulant Medication for ADHD and Associated Patterns of Substance Use: Preliminary Analysis Among College Students 
Journal of Pharmacy Practice  2011;24(6):551-560.
To explore the prevalence and characteristics associated with college students who misuse their prescribed stimulants for attention-deficit hyperactivity disorder (ADHD) and examine diversion and substance use behaviors as a function of misuse.
Cohort of 55 past-year prescribed stimulant users was identified from a random sample (n = 1738) at a large Midwestern research university following the self-administration of a web-based survey. An index was created to assess misuse of prescribed stimulants (i.e., Misuse Index).
Of 55 college students who reported past-year use of prescribed stimulants for ADHD, 22 (40%) endorsed at least one item on the misuse index. The most frequently endorsed misuse items were used too much (36%), self-reported misuse (19%), and intentionally used with alcohol or other drugs (19%). Misusers of prescribed stimulant medication were more likely to report cigarette smoking (p = 0.022), binge drinking (p = 0.022), illicit use of cocaine (p = 0.032), and screen positive on the Drug Abuse Screening test (DAST-10) criteria (p = 0.002). The bivariate odds ratio for the DAST-10 findings was 8.4 (95% CI: 2.0–34.6). Diversion of prescribed stimulants was common (36%) and occurred more frequently among stimulant misusers (57%; p = 0.008).
There is a strong relationship between misuse of prescribed stimulants for ADHD and substance use behaviors, as well as other deleterious behaviors such as diversion. These findings suggest the need for close screening, assessment, and therapeutic monitoring of medication use in the college population.
PMCID: PMC3277944  PMID: 22095577
attention-deficit hyperactivity disorder; medication; stimulant; misuse; diversion; amphetamine
3.  Addiction-Related Gene Regulation: Risks of Exposure to Cognitive Enhancers vs. Other Psychostimulants 
Progress in neurobiology  2012;100:60-80.
The psychostimulants methylphenidate (Ritalin, Concerta), amphetamine (Adderall), and modafinil (Provigil) are widely used in the treatment of medical conditions such as attention-deficit hyperactivity disorder and narcolepsy and, increasingly, as “cognitive enhancers” by healthy people. The long-term neuronal effects of these drugs, however, are poorly understood. A substantial amount of research over the past 2 decades has investigated the effects of psychostimulants such as cocaine and amphetamines on gene regulation in the brain because these molecular changes are considered critical for psychostimulant addiction. This work has determined in some detail the neurochemical and cellular mechanisms that mediate psychostimulant-induced gene regulation and has also identified the neuronal systems altered by these drugs. Among the most affected brain systems are corticostriatal circuits, which are part of cortico-basal ganglia-cortical loops that mediate motivated behavior. The neurotransmitters critical for such gene regulation are dopamine in interaction with glutamate, while other neurotransmitters (e.g., serotonin) play modulatory roles. This review presents (1) an overview of the main findings on cocaine- and amphetamine-induced gene regulation in corticostriatal circuits in an effort to provide a cellular framework for (2) an assessment of the molecular changes produced by methylphenidate, medical amphetamine (Adderall), and modafinil. The findings lead to the conclusion that protracted exposure to these cognitive enhancers can induce gene regulation effects in corticostriatal circuits that are qualitatively similar to those of cocaine and other amphetamines. These neuronal changes may contribute to the addiction liability of the psychostimulant cognitive enhancers.
PMCID: PMC3525776  PMID: 23085425
amphetamine; cocaine; cognitive enhancer; cortex; dopamine; gene regulation; methylphenidate; psychostimulant; striatum
4.  Adderall Induced Acute Liver Injury: A Rare Case and Review of the Literature 
Adderall (dextroamphetamine/amphetamine) is a widely prescribed medicine for the treatment of attention-deficit/hyperactivity disorder (ADHD) and is considered safe with due precautions. Use of prescribed Adderall without intention to overdose as a cause of acute liver injury is extremely rare, and to our knowledge no cases have been reported in the English literature. Amphetamine is an ingredient of recreational drugs such as Ecstacy and is known to cause hepatotoxicity. We describe here the case of a 55-year-old woman who developed acute liver failure during the treatment of ADHD with Adderall. She presented to the emergency room with worsening abdominal pain, malaise, and jaundice requiring hospitalization. She had a past history of partial hepatic resection secondary to metastasis from colon cancer which was under remission at the time of presentation. She recovered after intensive monitoring and conservative management. Adderall should be used carefully in individuals with underlying liver conditions.
PMCID: PMC3706063  PMID: 23864967
5.  Minimizing Adverse Events While Maintaining Clinical Improvement in a Pediatric Attention-Deficit/Hyperactivity Disorder Crossover Trial with Dextroamphetamine and Methylphenidate 
Objective: The purpose of this study was to investigate whether the availability of both dextroamphetamine and methylphenidate provides an opportunity to minimize adverse events in a pediatric attention-deficit/hyperactivity disorder (ADHD) stimulant trial.
Methods: Thirty-six medication-naïve children 9–14 years of age, diagnosed with ADHD, were enrolled for 6 weeks in a crossover trial, with 2 weeks of methylphenidate, dextroamphetamine, and a placebo in a randomly assigned, counterbalanced sequence. Barkley's Side-Effect Rating Scale (SERS), rated by parents, was used to assess adverse events. SERS were available for 34 children, and data were analyzed both at the group and the single-subject level.
Results: The side-effect profiles of dextroamphetamine and methylphenidate appeared similar at the group level. Overall, insomnia and decreased appetite were the only adverse events associated with the stimulants as compared with placebo. No significant increase from placebo to stimulant conditions was detected on SERS items reflecting emotional symptoms. Furthermore, dextroamphetamine and methylphenidate did not differ from each other on any SERS item, except that dextroamphetamine was associated with higher severity of “insomnia” and a higher prevalence of “unusually happy.” Single-subject analyses showed that one or more adverse events were reported in 14 children (41%), and were evenly distributed between those with dextroamphetamine as the drug that showed the greatest reduction in their ADHD symptoms (“best drug”) and those with methylphenidate as their best drug. Among children in whom both stimulants were associated with a decrease in ADHD symptoms, a clinically valid difference between the two stimulants in total adverse events score was found in 7 (39%) of the 18 cases. In these children, the availability of both stimulants provided an opportunity to minimize adverse events, while maintaining a reduction in ADHD symptoms.
Conclusions: The availability of both dextroamphetamine and methylphenidate may contribute to minimize adverse events in a subsample of children in pediatric ADHD stimulant trials.
Clinical Trials Registry: The study was first registered in clinical trials September 28, 2010. Clinical Identifier: NCT01220440.
PMCID: PMC3993015  PMID: 24666268
6.  Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children 
The annual cut-off date of birth for entry to school in British Columbia, Canada, is Dec. 31. Thus, children born in December are typically the youngest in their grade. We sought to determine the influence of relative age within a grade on the diagnosis and pharmacologic treatment of attention-deficit/hyperactivity disorder (ADHD) in children.
We conducted a cohort study involving 937 943 children in British Columbia who were 6–12 years of age at any time between Dec. 1, 1997, and Nov. 30, 2008. We calculated the absolute and relative risk of receiving a diagnosis of ADHD and of receiving a prescription for a medication used to treat ADHD (i.e., methylphenidate, dextroamphetamine, mixed amphetamine salts or atomoxetine) for children born in December compared with children born in January.
Boys who were born in December were 30% more likely (relative risk [RR] 1.30, 95% confidence interval [CI] 1.23–1.37) to receive a diagnosis of ADHD than boys born in January. Girls born in December were 70% more likely (RR 1.70, 95% CI 1.53–1.88) to receive a diagnosis of ADHD than girls born in January. Similarly, boys were 41% more likely (RR 1.41, 95% CI 1.33–1.50) and girls 77% more likely (RR 1.77, 95% CI 1.57–2.00) to be given a prescription for a medication to treat ADHD if they were born in December than if they were born in January.
The results of our analyses show a relative-age effect in the diagnosis and treatment of ADHD in children aged 6–12 years in British Columbia. These findings raise concerns about the potential harms of overdiagnosis and overprescribing. These harms include adverse effects on sleep, appetite and growth, in addition to increased risk of cardiovascular events.
PMCID: PMC3328520  PMID: 22392937
7.  Judging Cheaters: Is Substance Misuse Viewed Similarly in the Athletic and Academic Domains? 
The present study examines how individuals judge others who use performance enhancing drugs in two different domains, the athletic domain and the academic domain. Approximately 1,200 males in their freshman year of college completed a questionnaire that included two scenarios. One scenario described an athlete who misused anabolic steroids to help him succeed at a sporting event. The other described a college student who misused Adderall to help him succeed on his midterm exams. Participants rated the extent to which they thought the target had cheated and the extent to which they felt the substances were necessary for success. Results showed participants believed the athlete was more of a cheater than the student, and this difference got larger as past prescription stimulant misuse increased. Results also demonstrated that participants felt Adderall was more necessary than anabolic steroids for bringing about success. Contributions to the literature on zero-sum and non zero-sum domains are discussed. Implications for future research and efforts to prevent substance misuse are described.
PMCID: PMC3445768  PMID: 22545584
performance enhancement; anabolic steroids; prescription stimulants; judgments
8.  Expectation to receive methylphenidate enhances subjective arousal but not cognitive performance 
Nonmedical use of prescription stimulant medication such as methylphenidate (MPH) has increased among college students over the past several years. Common motivations for use include enhancements in cognition and subjective arousal. As it is unclear whether stimulant medication exerts the same effect on healthy individuals as for those with ADHD, it is possible that many reported effects of prescription stimulants by healthy individuals may stem from placebo effects, which may be an important mechanism underlying initiation and maintenance of nonmedical use. This study examined whether placebo effects influence reports of subjective mood and cognitive performance among college students who endorsed several risk factors for prescription stimulant misuse (i.e., low GPA, fraternity/sorority involvement, binge drinking, cannabis use). Ninety-six subjects (60% male) completed a battery of cognitive tests and questionnaires assessing present mood state on two occasions. Forty-seven participants were randomized to an experimental condition and orally ingested what they believed to be MPH, though actually placebo, on one visit and received no medication on the other visit. The control group received no medication on either visit. During the administration visit, experimental participants reported feeling significantly more high and stimulated compared to the non-administration visit and to the control subjects. However, cognitive enhancement differences were not generally seen between visits or groups. This research demonstrates that placebo effects for prescription stimulants do influence subjective mood and may be implicated in nonmedical stimulant use. This knowledge may be useful in challenging prescription stimulant-related expectancies to decrease the prevalence of use among college students.
PMCID: PMC3590067  PMID: 21875224
prescription stimulants; placebo effects; expectancy effects; cognition; college students
9.  Environmental Enrichment Preceding Early Adulthood Methylphenidate Treatment Leads to Long Term Increase of Corticosterone and Testosterone in the Rat 
PLoS ONE  2011;6(7):e22059.
Attention-deficit/hyperactivity disorder (ADD/ADHD) has been emerging as a world-wide psychiatric disorder. There appears to be an increasing rate of stimulant drug abuse, specifically methylphenidate (MPH) which is the most common treatment for ADHD, among individuals who do not meet the criteria for ADHD and particularly for cognitive enhancement among university students. However, the long term effects of exposure to MPH are unknown. Thus, in light of a developmental approach in humans, we aimed to test the effects of adolescence exposure to enriched environment (EE) followed by MPH administration during early adulthood, on reactions to stress in adulthood. Specifically, at approximate adolescence [post natal days (PND) 30–60] rats were reared in EE and were treated with MPH during early adulthood (PND 60–90). Adult (PND 90–92) rats were exposed to mild stress and starting at PND 110, the behavioral and endocrine effects of the combined drug and environmental conditions were assessed. Following adolescence EE, long term exposure to MPH led to decreased locomotor activity and increased sucrose preference. EE had a beneficial effect on PPI (attentive abilities), which was impaired by long term exposure to MPH. Finally, the interaction between EE and, exposure to MPH led to long-term elevated corticosterone and testosterone levels. In view of the marked increase in MPH consumption over the past decade, vigilance is crucial in order to prevent potential drug abuse and its long term detrimental consequences.
PMCID: PMC3137618  PMID: 21789212
10.  Persistent nonmedical use of prescription stimulants among college students: Possible association with ADHD symptoms 
Journal of attention disorders  2010;15(5):347-356.
To investigate the possible association between untreated Attention Deficit Hyperactivity Disorder (ADHD) symptoms, as measured the Adult ADHD Self-Report Scale, and persistent nonmedical use of prescription stimulants.
Multinomial regression modeling was used to compare ADHD symptoms among three groups of college students enrolled in a longitudinal study over four years: 1) persistent nonmedical users of prescription stimulants; 2) persistent users of marijuana who did not use prescription stimulants nonmedically; and, 3) consistent non-users of drugs.
ADHD symptoms were associated with being a persistent nonmedical user of prescription stimulants, after adjustment for race/ethnicity, sex, SES, and other illicit drug use. No associations were observed between ADHD symptoms and being a persistent marijuana user or non-user.
ADHD symptoms, and in particular inattention symptoms, appear to be associated with nonmedical use of prescription stimulants. Future studies are needed to clinically validate these observations.
PMCID: PMC2939927  PMID: 20484709
Amphetamine-like psychostimulant drugs have been used for decades to treat a variety of clinical conditions. Methylphenidate (MPH) - RitalinR, a compound that blocks reuptake of synaptically released norepinephrine (NE) and dopamine (DA) in the brain, has been used for more than 30 years in low dose, long-term regimens to treat attention deficit-hyperactive disorder (ADHD) in juveniles, adolescents, and adults. These agents are now also becoming increasingly popular among healthy individuals from all walks of life (e.g. military, students) and age groups (teenagers thru senior citizens) to promote wakefulness and improve attention. While there is agreement regarding the primary biochemical action of MPH, the physiological basis for its efficacy in normal individuals and ADHD patients is lacking. Study of the behavioral and physiological actions of clinically and behaviorally relevant doses of MPH in normal animals provides an opportunity to explore the role of catecholamine transmitters in prefrontal cortical function and attentional processes as they relate to normal operation of brain circuits and ADHD pathology. The goal of ongoing studies has been to: 1) assess the effects of low dose MPH on rodent performance in a well characterized sensory-guided sustained attention task, 2) examine the effects of the same low-dose chronic MPH administration on task-related discharge of prefrontal cortical (PFC) neurons and 3) investigate the effects of NE and DA on membrane response properties and synaptic transmission in identified subsets of PFC neurons. Combinations of these approaches can be used in adolescent, adult and aged animals to identify the parameters of cell and neural circuit function that are regulated by MPH and to establish an overarching explanation of how MPH impacts PFC operations from cellular through behavioral functional domains.
PMCID: PMC3514444  PMID: 21901844
12.  The epidemiology of pharmacologically treated attention deficit hyperactivity disorder (ADHD) in children, adolescents and adults in UK primary care 
BMC Pediatrics  2012;12:78.
Attention Deficit Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder characterised by the symptoms of inattention, impulsivity and hyperactivity. ADHD was once perceived as a condition of childhood only; however increasing evidence has highlighted the existence of ADHD in older adolescents and adults. Estimates for the prevalence of ADHD in adults range from 2.5–4%. Few data exist on the prescribing trends of the stimulants methylphenidate and dexamfetamine, and the non-stimulant atomoxetine in the UK. The aim of this study was to investigate the annual prevalence and incidence of pharmacologically treated ADHD in children, adolescents and adults in UK primary care.
The Health Improvement Network (THIN) database was used to identify all patients aged over 6 years with a diagnosis of ADHD/hyperkinetic disorder and a prescription for methylphenidate, dexamfetamine or atomoxetine from 2003–2008. Annual prevalence and incidence of pharmacologically treated ADHD were calculated by age category and sex.
The source population comprised 3,529,615 patients (48.9% male). A total of 118,929 prescriptions were recorded for the 4,530 patients in the pharmacologically treated ADHD cohort during the 6-year study. Prevalence (per 1000 persons in the mid-year THIN population) increased within each age category from 2003 to 2008 [6–12 years: from 4.8 (95% CI: 4.5–5.1) to 9.2 (95% CI: 8.8–9.6); 13–17 years: from 3.6 (95% CI: 3.3–3.9) to 7.4 (95% CI: 7.0–7.8); 18–24 years: from 0.3 (95% CI: 0.2–0.3) to 1.1 (95% CI: 1.0–1.3); 25–45 years: from 0.02 (95% CI: 0.01–0.03) to 0.08 (95% CI: 0.06–0.10); >45 years: from 0.01 (95% CI: 0.00–0.01) to 0.02 (95% CI: 0.01–0.03). Whilst male patients aged 6-12 years had the highest prevalence; the relative increase in prescribing was higher amongst female patients of the same age - the increase in prevalence in females aged 6–12 years was 2.1 fold compared to an increase of 1.9 fold for their male counterparts. Prevalence of treated ADHD decreased with increasing age. Incidence (per 1000 persons at risk in the mid-year THIN population) was highest for children aged 6–12 years.
A trend of increasing prescribing prevalence of ADHD drug treatment was observed over the period 2003–2008. Prevalence of prescribing to adult patients increased; however the numbers treated are much lower than published estimates of the prevalence of ADHD. This study has added to the limited knowledge on ADHD prescribing in primary care, particularly in the area of drug treatment in adulthood.
PMCID: PMC3472167  PMID: 22712630
13.  Misuse of Methamphetamine and Prescription stimulants among Youths and Young Adults in the Community 
Drug and alcohol dependence  2007;89(2-3):195-205.
Gender differences in the prevalence and characteristics of misuse of methamphetamine (meth) and prescription stimulants were examined in a representative U.S. sample of youths and young adults aged 16–25 (N = 24,409).
Stimulant misusers were categorized into three mutually exclusive subgroups: meth users only, meth and prescription stimulant users, and prescription stimulant users only (e.g., Benzedrine®, Ritalin®, or Dexedrine®). Multinominal logistic regression analyses identified the characteristics associated with misuse of meth and prescription stimulants.
About 1 in 10 youths reported any misuse of stimulants in their lifetime. Prescription stimulant misuse occurred earlier and was more frequent than meth misuse. About 47% of meth misusers also reported prescription stimulant misuse. Among misusers of meth and prescription stimulants, males were more likely than females to misuse methylphenidate (82% vs. 65%) but were less likely to misuse diet pills or amphetamines (37% vs. 49%). Multinominal logistic regression analyses indicated that all subgroups of lifetime stimulant misuse were associated with past year substance abuse. The characteristics of meth misusers differed slightly from prescription stimulants misusers.
Multidrug use is common among stimulant misusers. Parents should be informed about the risk of prescription stimulant misuse by their youths.
PMCID: PMC2063507  PMID: 17257780
Gender differences; Methamphetamine; Methylphenidate; Prescription stimulants; Substance use disorders
14.  Impact of methylphenidate formulation on treatment patterns and hospitalizations: a retrospective analysis 
While stimulant therapy has been shown to be effective in the treatment of attention-deficit/hyperactivity disorder (ADHD), there is less information concerning differences between alternative stimulant medications. The purpose of this study is to examine how different formulations of methylphenidate (MPH) affect treatment patterns and hospitalizations.
From a large claims database we retrospectively identified individuals age 6 or older who were diagnosed with ADHD and who received either once daily, extended-release oral system methylphenidate (OROS® MPH) (e.g., Concerta®) or three-times daily immediate-release generic methylphenidate (TID MPH). There were 5,939 individuals included in the analysis – 4,785 who initiated therapy with OROS MPH and 1,154 who initiated therapy with TID MPH. We used Analyses of Covariance (ANCOVAs) to examine differences in treatment patterns between individuals who initiated therapy on OROS MPH and those who initiated therapy on TID MPH. We used logistic and negative binomial multivariate regressions to examine the probability of being hospitalized and the hospital length of stay.
Controlling for demographic characteristics, patient general health status, and comorbid diagnoses, significantly fewer individuals who initiated therapy with OROS MPH had a 15-day gap in therapy (85% vs. 97%, p < 0.0001 or a 30-day gap in therapy (77% vs. 95%, p < 0.0001) or switched to another ADHD medication (27% vs. 68%, p < 0.0001). Individuals who initiated therapy with OROS MPH stayed on therapy significantly longer (199 vs. 108 mean days, p < 0.0001) and more individuals received medication for 90% (24% vs. 5%, p < 0.0001), 80% (29% vs. 7%, p < 0.0001), or 75% (30% vs. 7%, p < 0.0001) of the days during the first year post initiation of therapy. Individuals who initiated therapy on OROS MPH were also significantly less likely to be hospitalized (odds ratio = 0.67, p = 0.0454) and stayed, on average, 0.69 fewer days in the hospital (p = 0.0035).
Results demonstrate that among individuals diagnosed with ADHD who receive either OROS MPH or TID MPH, the use of OROS MPH is associated with fewer gaps in medication, less switches in medication, and more days on intent-to-treat therapy. In addition, use of OROS MPH compared to TID MPH was associated with improved outcomes, as measured by the reduced use of hospitalizations.
PMCID: PMC1462992  PMID: 16606463
15.  Management of attention-deficit hyperactivity disorder 
Attention-deficit hyperactivity disorder (ADHD/ADD) is a neurobehavioral disorder of childhood onset characterized by severe, developmentally inappropriate motor hyperactivity, inattention, and impulsiveness that result in impairment in more than one setting. It affects the home, school, and community life of 39% of school-going children worldwide. There is increasing recognition that ADHD symptoms and clinically defined disorder can persist into adult life and are associated with later drug and alcohol misuse and social and work difficulties. Added to that is the extreme variability of the disorder over time, within the same individual, between individuals, and across different circumstances. Treatment with stimulants and nonstimulants has proven effective in different subgroups, with the effectiveness of specific agents most likely related to the primary neurotransmitter involved. However, stimulants with a short duration of action have been problematic for some patients. Parent training and cognitive behavioral therapies represent the most widely adjunct psychosocial interventions to pharmacotherapy.
PMCID: PMC3173906  PMID: 21977081
Attention-deficit hyperactivity disorder; stimulants; atomoxetine
16.  High dose methylphenidate treatment in adult attention deficit hyperactivity disorder: a case report 
Stimulant medication improves hyperactivity, inattention, and impulsivity in both pediatric and adult populations with Attention Deficit Hyperactivity Disorder (ADHD). However, data regarding the optimal dosage in adults is still limited.
Case presentation
We report the case of a 38-year-old Caucasian patient who was diagnosed with Attention Deficit Hyperactivity Disorder when he was nine years old. He then received up to 10 mg methylphenidate (Ritalin®) and 20 mg sustained-release methylphenidate (Ritalin SR®) daily. When he was 13, his medication was changed to desipramine (Norpramin®), and both Ritalin® and Ritalin SR® were discontinued; and at age 18, when he developed obsessive-compulsive symptoms, his medication was changed to clomipramine (Anafranil®) 75 mg daily. Still suffering from inattention and hyperactivity, the patient began college when he was 19, but did not receive stimulant medication until three years later, when Ritalin® 60 mg daily was re-established. During the 14 months that followed, he began to use Ritalin® excessively, both orally and rectally, in dosages from 4800-6000 mg daily. Four years ago, he was referred to our outpatient service, where his Attention Deficit Hyperactivity Disorder was re-evaluated. At that point, the patient’s daily Ritalin® dosage was reduced to 200 mg daily orally, but he still experienced pronounced symptoms of, Attention Deficit Hyperactivity Disorder so this dosage was raised again. The patient’s plasma levels consistently remained between 60–187 nmol/l—within the recommended range—and signs of his obsessive-compulsive symptoms diminished with fluoxetine 40 mg daily. Finally, on a dosage of 378 mg extended-release methylphenidate (Concerta®), his symptoms of Attention Deficit Hyperactivity Disorder have improved dramatically and no further use of methylphenidate has been recorded during the 24 months preceding this report.
Symptoms of Attention Deficit Hyperactivity Disorder (ADHD) in this adult patient, who also manifested a co-occurring obsessive compulsive disorder, dramatically improved only after application of a higher-than-normal dose of methylphenidate. We therefore suggest that clinicians consider these findings in relation to their adherence to current therapeutic guidelines.
PMCID: PMC3407707  PMID: 22583957
17.  Behavioral sensitization and cross-sensitization between methylphenidate amphetamine, and 3-4, methylenedioxymethamphetamine (MDMA) in female SD rats 
European journal of pharmacology  2011;661(0):72-85.
The psychostimulants amphetamine and methylphenidate (MPD / Ritalin) are the drugs most often used to treat attention deficit hyperactivity disorder (ADHD). In addition, students of all ages take these drugs to improve academic performance but also abuse them for pleasurable enhancement. In addition, other psychostimulants such 3,4 methylenedioxymethamphetamine (MDMA / ecstasy) are used / abused for similar objectives. One of the experimental markers for the potential of a drug to produce dependence is its ability to induce behavioral sensitization and cross sensitization with other drugs of abuse. The objective of this study is to use identical experimental protocols and behavioral assays to compare in female rats the effects of amphetamine, MPD and MDMA on locomotor activity and to determine if they induce behavioral sensitization and/or cross sensitization with each other. The main findings of this study are 1. Acute amphetamine, MPD and MDMA all elicited increases in locomotor activity. 2. Chronic administration of an intermediate dose of amphetamine or MPD elicited behavioral sensitization. 3. Chronic administration of MDMA elicited behavioral sensitization in some animals and behavioral tolerance in others. 4. Cross sensitization between MPD and amphetamine was observed. 5. MDMA did not show either cross sensitization or cross tolerance with amphetamine. In conclusion, these results suggest that MDMA act by different mechanisms compared to MPD and amphetamine.
PMCID: PMC4036816  PMID: 21549116
Ritalin; Amphetamine; Ecstasy; locomotor; cross-sensitization; female rats
18.  Efficacy of lisdexamfetamine dimesylate in children with attention-deficit/hyperactivity disorder previously treated with methylphenidate: a post hoc analysis 
Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral psychiatric disorder that afflicts children, with a reported prevalence of 2.4% to 19.8% worldwide. Stimulants (methylphenidate [MPH] and amphetamine) are considered first-line ADHD pharmacotherapy. MPH is a catecholamine reuptake inhibitor, whereas amphetamines have additional presynaptic activity. Although MPH and amphetamine can effectively manage ADHD symptoms in most pediatric patients, many still fail to respond optimally to either. After administration, the prodrug stimulant lisdexamfetamine dimesylate (LDX) is converted to l-lysine and therapeutically active d-amphetamine in the blood. The objective of this study was to evaluate the clinical efficacy of LDX in children with ADHD who remained symptomatic (ie, nonremitters; ADHD Rating Scale IV [ADHD-RS-IV] total score > 18) on MPH therapy prior to enrollment in a 4-week placebo-controlled LDX trial, compared with the overall population.
In this post hoc analysis of data from a multicenter, randomized, double-blind, forced-dose titration study, we evaluated the clinical efficacy of LDX in children aged 6-12 years with and without prior MPH treatment at screening. ADHD symptoms were assessed using the ADHD-RS-IV scale, Conners' Parent Rating Scale-Revised short form (CPRS-R), and Clinical Global Impressions-Improvement scale, at screening, baseline, and endpoint. ADHD-RS-IV total and CPRS-R ADHD Index scores were summarized as mean (SD). Clinical response for the subgroup analysis was defined as a ≥ 30% reduction from baseline in ADHD-RS-IV score and a CGI-I score of 1 or 2. Dunnett test was used to compare change from baseline in all groups. Number needed to treat to achieve one clinical responder or one symptomatic remitter was calculated as the reciprocal of the difference in their proportions on active treatment and placebo at endpoint.
Of 290 randomized participants enrolled, 28 received MPH therapy at screening, of which 26 remained symptomatic (ADHD-RS-IV > 18). ADHD-RS-IV total scores, changes from baseline, clinical responsiveness, and rates of symptomatic remission in this subgroup were comparable to the overall population. The safety and tolerability profiles for LDX were comparable to other stimulants currently available.
In this analysis, children with significant clinical ADHD symptoms despite MPH treatment improved during treatment with LDX and experienced similar improvements in their symptoms as the overall study population.
Trial Registration NCT00556296
PMCID: PMC3225298  PMID: 22054243
Attention-deficit/hyperactivity disorder (ADHD); lisdexamfetamine dimesylate (LDX); methylphenidate; children; efficacy
19.  The Effects of Methylphenidate on Discounting of Delayed Rewards in ADHD 
Impulsivity is a central component of attention-deficit/hyperactivity disorder (ADHD). Delay discounting, or a preference for smaller, immediate rewards over larger, delayed rewards is considered an important aspect of impulsivity, and delay-related impulsivity has been emphasized in etiological models of ADHD. The current study examined whether stimulant medication, an effective treatment for ADHD, reduces discounting of delayed experiential and hypothetical rewards among 49 children (age 9–12 years) with ADHD. Following a practice day, participants completed a 3-day double-blind placebo-controlled acute medication assessment. Active doses were long-acting methylphenidate (Concerta), with the nearest equivalents of 0.3 and 0.6 mg/kg TID immediate-release methylphenidate. On each testing day, participants completed experiential (real-world money in real time) and hypothetical discounting tasks. Relative to placebo, methylphenidate reduced discounting of delayed experiential rewards, but not hypothetical rewards. Broadly consistent with etiological models that emphasize delay-related impulsivity among children with ADHD, these findings provide initial evidence that stimulant medication reduces delay discounting among those with the disorder. The present results also draw attention to task parameters that may influence the sensitivity of various delay discounting measures to medication effects.
PMCID: PMC2908283  PMID: 19803628
20.  Understanding the Effects of Stimulant Medications on Cognition in Individuals with Attention-Deficit Hyperactivity Disorder: A Decade of Progress 
Neuropsychopharmacology  2010;36(1):207-226.
The use of stimulant drugs for the treatment of children with attention-deficit hyperactivity disorder (ADHD) is one of the most widespread pharmacological interventions in child psychiatry and behavioral pediatrics. This treatment is well grounded on controlled studies showing efficacy of low oral doses of methylphenidate and amphetamine in reducing the behavioral symptoms of the disorder as reported by parents and teachers, both for the cognitive (inattention and impulsivity) and non-cognitive (hyperactivity) domains. Our main aim is to review the objectively measured cognitive effects that accompany the subjectively assessed clinical responses to stimulant medications. Recently, methods from the cognitive neurosciences have been used to provide information about brain processes that underlie the cognitive deficits of ADHD and the cognitive effects of stimulant medications. We will review some key findings from the recent literature, and then offer interpretations of the progress that has been made over the past decade in understanding the cognitive effects of stimulant medication on individuals with ADHD.
PMCID: PMC3055506  PMID: 20881946
methylphenidate; amphetamine; dopamine; prefrontal cortex; executive function; cognitive enhancement; psychostimulants; neuropharmacology; development/developmental disorders; neurochemistry; ADHD; methylphenidate; stimulants
21.  An update on the pharmacotherapy of attention-deficit/hyperactivity disorder in adults 
Expert review of neurotherapeutics  2011;11(10):1443-1465.
Adults with attention-deficit/hyperactivity disorder (ADHD) are more frequently presenting for diagnosis and treatment. Medication is considered to be appropriate among available treatments for ADHD; however, the evidence supporting the use of pharmacotherapeutics for adults with ADHD remains less established. In this article, the effectiveness and dosing parameters of the various agents investigated for adult ADHD are reviewed. In adults with ADHD, short-term improvements in symptomatology have been documented through the use of stimulants and antidepressants. Studies suggest that methylphenidate and amphetamine maintained an immediate onset of action, whereas the ADHD response to the nonstimulants appeared to be delayed. At a group level, there appears to be some, albeit not entirely consistent, dose-dependent responses to amphetamine and methylphenidate. Generally speaking, variability in diagnostic criteria, dosing parameters and response rates between the various studies was considerable, and most studies were of a relatively short duration. The aggregate literature shows that the stimulants and catecholaminergic nonstimulants investigated had a clinically significant beneficial effect on treating ADHD in adults.
PMCID: PMC3229037  PMID: 21955201
adult; amphetamine; antidepressants; atomoxetine; attention-deficit/hyperactivity disorder; methylphenidate; pharmacotherapy; stimulants
22.  ADHD in adolescence and adulthood, with a special focus on the dopamine transporter and nicotine 
The persistence of attention deficit hyperactivity disorder (ADHD) into adolescence and adulthood has now been accepted as a clinical entity. The rate of prevalence among adults is assumed to be from 2% to 4%. With increasing age, a symptom change has to be considered; disturbance of attention becomes more prominent, whereas hyperactivity often diminishes or changes to inactivity. Neuroimaging studies show a high striatal dopamine transporter (DAT) availability in most adults with ADHD; this can be reduced by stimulants. Nicotine seems to have a stimulant-like action on the DAT. In most adults with ADHD, therapy has to be multimodal, combining psychotherapy and medication. Methylphenidate is the first-line drug in adult ADHD; further options are amphetamine and noradrenaline reuptake inhibitors. Nonresponders to methylphenidate seem to have no elevated DAT availability prior to therapy. Combination with other psychiatric disorders occurs frequently in adults with ADHD; in these patients additional pharmacological treatment with special regard to the comorbid disease is recommended.
PMCID: PMC3181750  PMID: 16640111
attention deficit hyperactivity disorder; adolescence; adulthood; brain imaging techniques; single photon emission computed tomography; dopamine transporter; nicotine; diagnosis; therapy; methylphenidate
23.  Methylphenidate Enhances NMDA-Receptor Response in Medial Prefrontal Cortex via Sigma-1 Receptor: A Novel Mechanism for Methylphenidate Action 
PLoS ONE  2012;7(12):e51910.
Methylphenidate (MPH), commercially called Ritalin or Concerta, has been widely used as a drug for Attention Deficit Hyperactivity Disorder (ADHD). Noteworthily, growing numbers of young people using prescribed MPH improperly for pleasurable enhancement, take high risk of addiction. Thus, understanding the mechanism underlying high level of MPH action in the brain becomes an important goal nowadays. As a blocker of catecholamine transporters, its therapeutic effect is explained as being due to proper modulation of D1 and α2A receptor. Here we showed that higher dose of MPH facilitates NMDA-receptor mediated synaptic transmission via a catecholamine-independent mechanism, in layer V∼VI pyramidal cells of the rat medial prefrontal cortex (PFC). To indicate its postsynaptic action, we next found that MPH facilitates NMDA-induced current and such facilitation could be blocked by σ1 but not D1/5 and α2 receptor antagonists. And this MPH eliciting enhancement of NMDA-receptor activity involves PLC, PKC and IP3 receptor mediated intracellular Ca2+ increase, but does not require PKA and extracellular Ca2+ influx. Our additional pharmacological studies confirmed that higher dose of MPH increases locomotor activity via interacting with σ1 receptor. Together, the present study demonstrates for the first time that MPH facilitates NMDA-receptor mediated synaptic transmission via σ1 receptor, and such facilitation requires PLC/IP3/PKC signaling pathway. This novel mechanism possibly explains the underlying mechanism for MPH induced addictive potential and other psychiatric side effects.
PMCID: PMC3527396  PMID: 23284812
24.  Effects of stimulant medication on the lateralisation of line bisection judgements of children with attention deficit hyperactivity disorder 
OBJECTIVES—Deficits in the maintenance of attention may underlie problems in attention deficit hyperactivity disorder (ADHD). Children with ADHD also show asymmetric attention deficits in traditional lateralisation and visuospatial orienting tasks, suggesting right hemispheric (and left hemispace) attentional disturbance. This study aimed to examine the lateralisation of selective attention in ADHD; specifically, the effect of a moving, random dot background, and stimulant medication in the line bisection task.
METHODS—The performance of children with ADHD, on and off methylphenidate, was examined using a computerised horizontal line bisection task with moving and blank backgrounds. Twenty children with a DSM-IV diagnosis of ADHD participated with 20 controls, individually matched for age, sex, grade at school, and IQ. Twelve of the 20children with ADHD were on stimulant medication at the time of testing. Horizontal lines of varying length were presented in the centre of a computer screen, with either a blank background, or a moving, random dot field. The random dots moved either leftward or rightward across the screen at either 40 mm/s or 80 mm/s.
RESULTS—The children with ADHD off medication bisected lines significantly further to the right compared with controls, who showed a small leftward error. Methylphenidate normalised the performance of the children with ADHD for the task with the moving dots.
CONCLUSIONS—These results support previous evidence for a right hemispheric hypoarousal theory of attentional dysfunction, and are consistent with the emerging picture of a lateralised dysfunction of frontostriatal circuitry in ADHD.

PMCID: PMC1736185  PMID: 9886453
25.  Advances in understanding and treating ADHD 
BMC Medicine  2011;9:72.
Attention deficit hyperactivity disorder (ADHD) is a neurocognitive behavioral developmental disorder most commonly seen in childhood and adolescence, which often extends to the adult years. Relative to a decade ago, there has been extensive research into understanding the factors underlying ADHD, leading to far more treatment options available for both adolescents and adults with this disorder. Novel stimulant formulations have made it possible to tailor treatment to the duration of efficacy required by patients, and to help mitigate the potential for abuse, misuse and diversion. Several new non-stimulant options have also emerged in the past few years. Among these, cognitive behavioral interventions have proven popular in the treatment of adult ADHD, especially within the adult population who cannot or will not use medications, along with the many medication-treated patients who continue to show residual disability.
PMCID: PMC3126733  PMID: 21658285

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