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

ADHD Adults Show Lower Interindividual Similarity in Ex-Gaussian Reaction Time Vectors for Congruent Stimuli Compared to Control Peers

OBJECTIVE

Interindividual similarity refers to how similarly individuals respond when receiving the same stimulus or intervention. In this study, we aimed to examine interindividual similarity in adults with ADHD.

METHOD

We used the cosine similarity index of ex-Gaussian reaction time (RT) vectors of mu, sigma, and tau parameters during a Stroop task.

RESULTS

Our results demonstrate that the ADHD group exhibits a reduced interindividual similarity index in their ex-Gaussian RT vectors for congruent stimuli compared to the healthy control group. Importantly, we did not find significant differences in the interindividual similarity index to incongruent stimuli between both groups, thus suggesting that this reduced index was selective for congruent stimuli.

CONCLUSION

Our findings highlight that ADHD adults exhibit more significant interindividual differences in cognitive functioning when processing congruent stimuli than healthy controls. These results provide new insights into the selective mechanisms underlying ADHD and may contribute to developing new targeted interventions for this disorder.

Trapezoid bioequivalence: A rational bioavailability evaluation approach on account of the pharmaceutical‐driven balance of population average and variability

Among the current approaches for the analysis of bioequivalence, the average bioequivalence (ABE) is limited only to the mean bioavailability, whereas the population bioequivalence (PBE) criterion aggregates both mean and variance in a general comparison formula. However, a rational bioequivalence criterion capable of judging specific drug considerations is always still preferred. As an alternative approach, we introduce an aggregate criterion, namely, the trapezoid bioequivalence (TBE), which includes the consideration of both mean and variance of the bioavailability and adapted weighting of a drug's therapeutic properties. We first applied our method to specific simulated scenarios to compare the strengths and weaknesses of current bioequivalence approaches and demonstrate the improvements brought by TBE. As well, the impact of sample size and variability on ABE, PBE, and TBE are assessed using a population pharmacokinetic model of methylphenidate. Our results indicate that TBE inherits the advantages of both ABE and PBE while greatly reducing their inadequacies. Through simulations with population pharmacokinetic models of specific scenarios, we confirm that (1) TBE does not encounter the overly permissiveness issue of PBE, (2) TBE respects the hierarchy to ABE (TBE => ABE), and (3) TBE assesses bioequivalence with a restriction on σT2‐σR2 without an increase to type 2 errors. The clinically inspired simulations demonstrate TBE’s superiority in a realistic context and its potential usefulness in practice. Moreover, the parameter choice in TBE may be adapted according to the specific context of a drug's pharmacological and pharmacodynamic properties.

DSM-5 Adult Attention-Deficit/Hyperactivity Disorder: Sex Differences in EEG Activity

This study examined sex differences in the EEG of adults diagnosed with Attention-Deficit/Hyperactivity Disorder (AD/HD) according to DSM-5 criteria. Sixteen females and 16 males with AD/HD, and age- and sex-matched control groups, had an eyes-closed resting EEG recorded from 19 electrode sites. EEGs were Fast Fourier transformed and estimates for total power, absolute and relative power in the delta, theta, alpha, beta and gamma bands, and the theta/beta ratio, were analysed across nine cortical regions. Males with AD/HD, compared with male controls, had globally reduced absolute beta, globally elevated relative theta, and a larger theta/beta ratio. In contrast, no global effects emerged between females with and without AD/HD. Significant group interactions indicated that globally elevated relative theta and elevated frontal-midline theta/beta ratio noted in males with AD/HD differed significantly from results in females. There are statistically significant EEG differences in relative theta and the theta/beta ratio between males and females with and without AD/HD. These results indicate that AD/HD affects the EEG activity of males and females differently. This study helps confirm the need for further independent examination of AD/HD within female populations.

Stability of Methylphenidate under Various pH Conditions in the Presence or Absence of Gut Microbiota

Methylphenidate is one of the most widely used oral treatments for attention-deficit/hyperactivity disorder (ADHD). The drug is mainly absorbed in the small intestine and has low bioavailability. Accordingly, a high interindividual variability in terms of response to the treatment is known among ADHD patients treated with methylphenidate. Nonetheless, very little is known about the factors that influence the drug's absorption and bioavailability. Gut microbiota has been shown to reduce the bioavailability of a wide variety of orally administered drugs. Here, we tested the ability of small intestinal bacteria to metabolize methylphenidate. In silico analysis identified several small intestinal bacteria to harbor homologues of the human carboxylesterase 1 enzyme responsible for the hydrolysis of methylphenidate in the liver into the inactive form, ritalinic acid. Despite our initial results hinting towards possible bacterial hydrolysis of the drug, up to 60% of methylphenidate is spontaneously hydrolyzed in the absence of bacteria and this hydrolysis is pH-dependent. Overall, our results indicate that the stability of methylphenidate is compromised under certain pH conditions in the presence or absence of gut microbiota.

Clinically Significant Drug-Drug Interactions with Agents for Attention-Deficit/Hyperactivity Disorder

This article provides an overview of the pharmacokinetic drug-drug interactions (DDIs) for agents prescribed for attention-deficit/hyperactivity disorder (ADHD). Polypharmacy in the treatment of patients with ADHD leads to high exposures to DDIs and possibly adverse safety outcomes. We performed a systematic search of DDI reports for ADHD agents in Embase and Medline. We also searched for agents in the pharmacological pipeline, which include (1) mazindol, molindone and viloxazine, which were previously prescribed for other indications; (2) centanafadine and AR-08, never before approved; and (3) two extracts (Polygala tenuifolia extract and the French maritime pine bark extracts). The identified literature included case reports, cross-sectional, cross-over and placebo-controlled studies of patient cohorts and healthy volunteers. The DDIs were classified as follows: ADHD agents acting as perpetrators, i.e., affecting the clearance of co-prescribed agents (victim drugs), or ADHD agents being the victim drugs, being affected by other agents. Ratios for changes in pharmacokinetic parameters before and after the DDI were used as a rough estimate of the extent of the DDI. Alcohol may increase plasma dextroamphetamine concentrations by presystemic effects. Until studies are done to orient clinicians regarding dosing changes, clinicians need to be aware of the potential for cytochrome P450 (CYP) 2D6 inhibitors to increase amphetamine levels, which is equivalent to increasing dosages. Atomoxetine is a wide therapeutic window drug. The CYP2D6 poor metabolizers who do not have CYP2D6 activity had better atomoxetine response, but also an increased risk of adverse effects. CYP2D6 inhibitors have been used to increase atomoxetine response in CYP2D6 extensive metabolizers. Guanfacine is mainly metabolized by CYP3A4, which can be induced and inhibited. The package insert recommends that in guanfacine-treated patients, after adding potent CYP3A4 inducers, the guanfacine dose should be doubled; after adding potent CYP3A4 inhibitors the guanfacine dose should be halved. Based on a phenobarbital case report and our experience with CYP3A4-metabolized antipsychotics, these correction factors may be too low. According to two case reports, carbamazepine is a clinically relevant inducer of methylphenidate (MPH). A case series study suggested that MPH may be associated with important elevations in imipramine concentrations. Due to the absence of or limitations in the data, no comments for clinicians can be provided on the pharmacokinetic DDIs for clonidine, centanafadine, mazindol, molindone, AR-08, P. tenuifolia extract and the French maritime pine bark extracts. According to currently available data, clinicians should not expect that ADHD drugs modify each other's serum concentrations. A summary table for clinicians provides our current recommendations on pharmacokinetic DDIs of ADHD agents based on our literature review and the package inserts; whenever it was possible, we provide information on serum concentrations and dose correction factors. There will be a need to periodically update these recommendations and these correction factors as new knowledge becomes available.

A phase 1, randomized, double-blind, placebo-controlled study to evaluate the safety, tolerability, and pharmacokinetics of single and multiple doses of lisdexamfetamine dimesylate in Japanese and Caucasian healthy adult subjects

Aim

To assess safety, tolerability, and pharmacokinetics of lisdexamfetamine dimesylate in Japanese and Caucasian healthy adults.

Methods

A phase 1, double‐blind, randomized, placebo‐controlled, single‐ and multiple‐dose study in Japanese and Caucasian subjects. Subjects received lisdexamfetamine 20 mg or placebo on Day 1, then lisdexamfetamine 20 mg/d (Days 4‐8), 50 mg/d (Days 9‐13), 70 mg/d (Days 14‐18), or matching placebo. Pharmacokinetic parameters for lisdexamfetamine and d‐amphetamine were estimated by noncompartmental analysis.

Results

Fifteen Japanese and 19 Caucasian subjects were enrolled and randomized. The lisdexamfetamine and d‐amphetamine plasma concentration‐time curves were similar for both ethnic groups following single and multiple doses. Mean area under the concentration‐time curves for d‐amphetamine were higher (by 11%‐15%) in Japanese than Caucasian subjects following multiple dosing of lisdexamfetamine. Mean bodyweight was 17% lower in Japanese than Caucasian subjects. Weight‐corrected means for oral clearance were similar in both ethnic groups, with no unexpected accumulation of d‐amphetamine. Lisdexamfetamine was generally well tolerated by both ethnic groups, with no serious adverse events reported. The 10/12 Japanese and 11/16 Caucasian subjects who received lisdexamfetamine completed the study; two Japanese and three Caucasian subjects discontinued due to adverse events. Most adverse events were of mild severity.

Conclusion

Pharmacokinetics were generally similar for Japanese and Caucasian subjects; the minor differences observed were likely due to bodyweight differences in the two ethnic groups. Lisdexamfetamine was generally well tolerated. Adverse events were consistent with the established safety profile of lisdexamfetamine and were similar in both ethnic groups.

This phase 1, double‐blind, randomized, placebo‐controlled study was conducted to assess safety, tolerability, and pharmacokinetics of lisdexamfetamine dimesylate in Japanese and Caucasian subjects. Fifteen Japanese and 19 Caucasian subjects were enrolled and randomized to receive lisdexamfetamine 20 mg (Day 1), 20 mg/d (Days 4‐8), 50 mg/d (Days 9‐13), and 70 mg/d (Days 14‐18), or matching placebo. Pharmacokinetics were generally similar for Japanese and Caucasian subjects; minor differences observed were likely due to bodyweight differences in the two ethnic groups, and lisdexamfetamine was generally well tolerated.

An update on the pharmacokinetic considerations in the treatment of ADHD with long-acting methylphenidate and amphetamine formulations

Introduction: Long-acting stimulant formulations are recommended as first-line pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD). Over the past 20 years, extended-release (ER) methylphenidate (MPH) and amphetamine (AMP) formulations have evolved to include varying drug delivery technologies, enantiomers/salts, and dosage forms. All formulations are characterized by a unique pharmacokinetic profile that is closely mirrored by pharmacodynamic response allowing clinicians to individualize therapy based on their patient's clinical needs and dosing preferences.Areas covered: This review provides an update on the pharmacokinetic properties of approved and investigational ER MPH and AMP formulations and highlights pharmacokinetic features that clinicians should consider when selecting a long-acting stimulant.Expert opinion: Since there are no reliable biomarkers that can predict individualized response to long-acting stimulants, clinicians need to consider their distinctive pharmacokinetic properties, including the pharmacokinetic profile, rate and extent of absorption, variability, dose proportionality, bioequivalence, and potential for accumulation. Clinicians also need to understand that certain factors can contribute to increased variability in pharmacokinetics and potentially affect outcomes. Less invasive, high-throughput techniques and novel time-based scales are being developed to advance research on the pharmacokinetic-pharmacodynamic relationships of stimulants. Model-based pharmacokinetic-pharmacodynamic approaches can be applied to aid the development of novel formulations and individualize therapy with existing drugs.

A Quantitative Comparison Approach for Methylphenidate Drug Regimens in Attention-Deficit/Hyperactivity Disorder Treatment

OBJECTIVE

Different methylphenidate (MPH) formulations, immediate release (IR) or extended release (ER), have been developed to treat Attention-Deficit/Hyperactivity Disorder (ADHD). A better use of these formulations, with a proper choice of their timing, dosage, and combination, can help to attain optimal therapeutic effect while maintaining a good quality of life. In this study, we aim at presenting a quantitative comparison approach to help identify drug regimens that provide best therapeutic performances and respect patients' specific needs.

METHODS

Using pharmacokinetic (PK) models of various MPH formulations constructed with data in hand and a formerly developed performance metric for MPH regimens, we proposed a statistical integral strategy for regimen comparison, which comprises a sequential, a relative, and a probability-over-threshold method. The first is hierarchical in nature and sequentially compares the regimen performance, the total daily dose, and the administration frequency. The second compares two regimens by quantifying their similarity. The third computes the probability of an incremental regimen performance over a specified threshold. The first two comparison approaches are used for naive patients, whereas the third one is for patients under treatment.

RESULTS

PK models of one compartment effectively describe both the IR and ER data. Applied to three frequent MPH clinical situations, the three-methods strategy is able to distinguish the regimens proposed for each. A combined regimen of IR and ER taken at the same time performs better than a single ER dose.

CONCLUSION

The proposed statistical strategy is able to differentiate ADHD regimens in various clinically relevant situations, and adapt the use of MPH drugs to a patient's daily routine. Since it does not compare fixed doses and formulations but rather any MPH regimen, our approach generalizes the current context of bioequivalence study and provides an accessible computational tool for objectively selecting MPH regimens.

New stimulant formulations for pediatric attention-deficit/hyperactivity disorder: a case-based approach for the primary care provider

PURPOSE OF REVIEW

To provide an up-to-date clinical review of U.S. Food and Drug Administration (FDA)-approved stimulant medications for attention-deficit/hyperactivity disorder (ADHD), including a framework for individualized treatment by primary care pediatric providers.

RECENT FINDINGS

Stimulant medications are first-line agents for pediatric ADHD. Since 2012, 11 novel stimulant medications have been approved by the FDA for the treatment of ADHD. Because of an expanded formulary of available methylphenidate-based and amphetamine-based stimulants, primary care providers may be unfamiliar with some novel medications outside a select formulary.

SUMMARY

The current broad formulary of methylphenidate-based and amphetamine-based stimulants provides primary care clinicians with a greater opportunity for personalized medicine within the patient-centered medical home. Through a systematic review of prior relevant medication trials, a consideration of daily symptom burden and thoughtful pragmatics, primary care providers can offer a more precise, customized stimulant treatment.

Lisdexamfetamine Dimesylate: A Review in Paediatric ADHD

Lisdexamfetamine dimesylate (lisdexamfetamine; Elvanse^®; Tyvense^®), an orally-active dexamfetamine prodrug, is indicated in the EU for the treatment of attention-deficit hyperactivity disorder (ADHD) in children aged ≥ 6 years (including adolescents) when the response to previous methylphenidate (MPH) treatment is clinically inadequate. The original approval of the drug was based on the results of phase III trials in children and adolescents with ADHD who had an inadequate response to previous pharmacotherapy (e.g. MPH) or were treatment naïve. In these studies, short-term treatment with flexibly-dosed lisdexamfetamine demonstrated greater efficacy than atomoxetine, based on a prospective comparison, and osmotic-release oral system (OROS)-MPH, based on a post hoc comparison. Improvements in ADHD symptoms were accompanied by improvements in health-related quality of life and functioning that were maintained as long as treatment with lisdexamfetamine was continued in a long-term extension of one of these trials. In subsequent phase IV head-to-head studies in adolescents with ADHD and an inadequate response to previous pharmacotherapy, lisdexamfetamine demonstrated greater efficacy than OROS-MPH when both medications were force-titrated, but not when they were flexibly-titrated. Lisdexamfetamine was generally well tolerated, with an adverse event profile (e.g. decreased appetite, headache, weight reduction, insomnia and irritability) typical of that reported for other stimulants. Thus, lisdexamfetamine provides an alternative option for the treatment of children and/or adolescents with ADHD who have not responded adequately to previous ADHD pharmacotherapies.

Stimulant 'rapid metabolizers': wrong label, real phenomena

This is a review of the empirical literature regarding what has been described anecdotally as patients who are 'rapid metabolizers' of stimulant medication. The authors propose that this is a misnomer used to describe two types of atypical pharmacokinetic patterns of response: high-dose responders, short-duration responders and two types of atypical pharmacodynamics patterns of response: patients who develop either acute or chronic tolerance. The authors propose that use of more precise terminology should facilitate both patient education and research to better understand the physiology and clinical management of atypical response patterns to stimulant treatment. Presently, the understanding of the pharmacokinetics and pharmacodynamics of psychostimulants is still quite limited. Further scientific research is needed to understand unusual patterns of pharmacological response seen in the clinic. Careful identification and precise description of these patterns would facilitate understanding the pharmacokinetics and pharmacodynamics of stimulants impacts the atypical response patterns seen in the clinic.

Methylphenidate doses in Attention Deficit/Hyperactivity Disorder and comorbid substance use disorders

Patients with Attention Deficit/Hyperactivity Disorder (ADHD) and comorbid Substance Use Disorders (SUD) are increasingly being treated with central stimulant medication despite limited evidence for its effectiveness. Lack of longitudinal follow-up studies of dosing and adverse effects has resulted in conflicting treatment guidelines. This study aims to explore whether individuals with ADHD and comorbid SUD are treated with higher stimulant doses than individuals with ADHD only, and whether doses increase over time as a sign of tolerance, a core symptom of addiction. Information on methylphenidate doses for 14 314 Swedish adults, including 4870 individuals with comorbid SUD was obtained through linkages of Swedish national registers between 2006 and 2009. Differences in doses between patients with and without SUD were estimated using logistic regression while a linear regression model calculated time trends in mean doses. Individuals with SUD were prescribed higher methylphenidate doses than those without (OR_day365; 2.12, 95% CI 1.81-2.47: OR_day730 2.65, 95% CI 2.13-3.30). Patients with SUD were, two years after initiating stimulant treatment, prescribed approximately 40% higher doses compared to individuals with ADHD only. The results may suggest a need for increased doses in this population to achieve optimal ADHD symptom control. A tendency towards increasing doses during the first years of treatment, more pronounced in individuals with comorbid SUD, may reflect a reluctance to prescribe adequate doses due to lack of clinical guidelines. Mean doses stabilized after about two years in both groups, which does not lend support to continuously increasing tolerance over time.

Methylphenidate for Treating ADHD: A Naturalistic Clinical Study of Methylphenidate Blood Concentrations in Children and Adults With Optimized Dosage

Background

Methylphenidate (MPH), along with behavioral and psychosocial interventions, is the first-line medication to treat attention-deficit hyperactivity disorder (ADHD) in Sweden. The dose of MPH for good symptom control differs between patients. However, studies of MPH concentration measurement in ADHD treatment are limited.

Objective

To describe blood and oral fluid (OF) concentrations of MPH after administration of medication in patients with well-adjusted MPH treatment for ADHD, and to identify the most suitable matrix for accurate MPH concentration during treatment.

Methods

Patients were recruited from Child and Adolescent Psychiatry (CAP), General Psychiatry (GP), and the Department of Dependency (DD). Blood and OF samples were collected in the morning before MPH administration as well as 1 and 6 h after administration of the prescribed morning dose of MPH.

Results

Fifty-nine patients aged between 9 and 69 years, 76 % males. The daily dose of MPH varied from 18 to 180 mg, but the median daily dose per body weight was similar, approximately 1.0 mg/kg body weight. The median MPH concentration in blood 1 and 6 h after the morning dose was 5.4 and 9.3 ng/mL, respectively. Highly variable OF-to-blood ratios for MPH were found at all time points for all three groups.

Conclusions

Weight is a reliable clinical parameter for optimal dose titration. Otherwise, MPH blood concentration might be used for individual dose optimization and for monitoring of the prescribed dose. Relying only on the outcome in OF cannot be recommended for evaluation of accurate MPH concentrations for treatment monitoring.

Daily Symptom Profiles of Children With ADHD Treated With Modified-Release Methylphenidate

OBJECTIVE

The aim was to identify subgroups of patients with ADHD with different daily symptom profiles and to characterize their response to modified-release methylphenidate (MR MPH) treatment, using data from the observational trial OBSEER.

METHOD

OBSEER included patients aged 6 to 17 years receiving MR MPH under routine care. To detect subgroups, a latent class cluster analysis was applied. Sex, age, MR MPH dose, and emotional symptoms were considered predictors of response.

RESULTS

The analysis included 637 patients (81.3% male), with a mean age (standard deviation) of 10.1 (2.5) years. A two-class solution best fit the data, identifying a high-severity group (49.8%) with pronounced symptom reduction, and a low-severity group (50.2%) with minor changes throughout the day. Younger age, male sex, and higher MPH doses were predictive of the high-severity class.

CONCLUSION

Children with ADHD treated with MR MPH are heterogeneous, and subgroups with differential treatment response can be identified.

Lisdexamfetamine Dimesylate: Prodrug Delivery, Amphetamine Exposure and Duration of Efficacy

Lisdexamfetamine dimesylate (LDX) is a long-acting d-amphetamine prodrug used to treat attention-deficit/hyperactivity disorder (ADHD) in children, adolescents and adults. LDX is hydrolysed in the blood to yield d-amphetamine, and the pharmacokinetic profile of d-amphetamine following oral administration of LDX has a lower maximum plasma concentration (C_max), extended time to C_max (T_max) and lower inter- and intra-individual variability in exposure compared with the pharmacokinetic profile of an equivalent dose of immediate-release (IR) d-amphetamine. The therapeutic action of LDX extends to at least 13 h post-dose in children and 14 h post-dose in adults, longer than that reported for any other long-acting formulation. Drug-liking scores for LDX are lower than for an equivalent dose of IR d-amphetamine, which may result from the reduced euphorigenic potential associated with its pharmacokinetic profile. These pharmacokinetic and pharmacodynamic characteristics of LDX may be beneficial in the management of symptoms in children, adolescents and adults with ADHD.

Classics in Chemical Neuroscience: Methylphenidate

As the first drug to see widespread use for the treatment of attention deficit hyperactivity disorder (ADHD), methylphenidate was the forerunner and catalyst to the modern era of rapidly increasing diagnosis, treatment, and medication development for this condition. During its often controversial history, it has variously elucidated the importance of dopamine signaling in memory and attention, provoked concerns about pharmaceutical cognitive enhancement, driven innovation in controlled-release technologies and enantiospecific therapeutics, and stimulated debate about the impact of pharmaceutical sales techniques on the practice of medicine. In this Review, we will illustrate the history and importance of methylphenidate to ADHD treatment and neuroscience in general, as well as provide key information about its synthesis, structure-activity relationship, pharmacological activity, metabolism, manufacturing, FDA-approved indications, and adverse effects.

Efficacy of Methylphenidate Hydrochloride Extended-Release Capsules (Aptensio XR™) in Children and Adolescents with Attention-Deficit/Hyperactivity Disorder: A Phase III, Randomized, Double-Blind Study

BACKGROUND

Psychostimulants remain first-line treatment options for the management of attention-deficit/hyperactivity disorder (ADHD). A multilayer extended-release bead methylphenidate capsule (provisional name Aptensio XR™, MPH-MLR) with unique release properties is being investigated for the treatment of ADHD.

OBJECTIVE

The aim of this study was to assess the efficacy (primary) and safety and tolerability (secondary) of MPH-MLR compared with placebo in children and adolescents aged 6-18 years with ADHD.

METHODS

This study was a parallel, double-blind, multicenter, placebo-controlled, forced-dose, phase III study in which patients were randomized to placebo or MPH-MLR 10, 15, 20, or 40 mg given once daily. There were four study phases: (1) 4-week screening/baseline; (2) 1-week, double-blind treatment (DBP); (3) 11-week, open-label, dose-optimization period; and (4) 30-day follow-up call. During the open-label dose-optimization period all patients started with MPH-MLR 10 mg, unless the investigator deemed it necessary to begin at a higher dose, and were titrated to an optimized dose (10, 15, 20, 30, 40, 50, 60 mg; all given once daily) based on response and adverse events (AEs). The primary endpoint was the change from baseline to end of DBP in ADHD Rating Scale, 4th Edition (ADHD-RS-IV) total score. Secondary endpoints included changes in ADHD-RS-IV subscales and Clinical Global Impression-Improvement Scale (CGI-I) at the end of the DBP. The primary analysis was an analysis of covariance including terms for treatment, site, and baseline ADHD-RS-IV total score.

RESULTS

A total of 221 patients completed the DBP. The primary endpoint had a statistically significant difference among treatments (p = 0.0046) and sites (p = 0.0018), and baseline covariate made a significant contribution (p < 0.0001). As the MPH-MLR dose increased, the ADHD-RS-IV total score improved; the 20 and 40 mg doses were statistically different (p = 0.0145 and p = 0.0011, respectively) from placebo. Females responded differently than did males (p = 0.0238); there was a significant difference among treatments for males but not for females, partly because only one-third of subjects were female and partly because some females who received placebo had considerable improvement during the DBP. Similarly, the ADHD-RS-IV subscales and CGI-I scores at the end of the DBP also showed more improvement as the dose of MPH-MLR increased. During the open-label phase, ADHD-RS-IV total scores improved (mean change from baseline -22.5) and correlated as the dose of MPH-MLR increased; CGI-I scores also improved. No unexpected AEs were noted.

CONCLUSIONS

Dose-related improvements in ADHD-RS-IV scores that exceeded those of placebo were observed in patients treated with MPH-MLR. No new safety signals were noted.

Single-dose pharmacokinetics of methylphenidate extended-release multiple layer beads administered as intact capsule or sprinkles versus methylphenidate immediate-release tablets (Ritalin(®)) in healthy adult volunteers

OBJECTIVES

The purpose of this study was to evaluate the relative bioavailability and safety of a multilayer extended-release bead methylphenidate (MPH) hydrochloride 80 mg (MPH-MLR) capsule or sprinkles (37% immediate-release [IR]) versus MPH hydrochloride IR(Ritalin(®)) tablets, and to develop a pharmacokinetic (PK) model simulating MPH concentration-time data for different MPH-MLR dosage strengths.

METHODS

This was a single-center, randomized, open-label, three-period crossover study conducted in 26 fasted healthy adults (mean weight±standard deviation, 70.4±11.7 kg) assigned to single-dose oral MPH-MLR 80 mg capsule or sprinkles with applesauce, or Ritalin IR 25 mg (1×5 mg and 1×20 mg tablet) administered at 0, 4, and 8 hours.

RESULTS

MPH-MLR 80 mg capsule and sprinkles were bioequivalent; ratios for maximum concentration (Cmax), area under plasma drug concentration versus time curve (AUC)0-t, and AUC0-inf were 1.04 (95% confidence interval [CI], 96.3-112.4), 0.99 (95% CI, 95.3-102.8), and 0.99 (95% CI, 95.4-103.0), respectively. MPH-MLR capsule/sprinkles produced highly comparable, biphasic profiles of plasma MPH concentrations characterized by rapid initial peak, followed by moderate decline until 5 hours postdose, and gradual increase until 7 hours postdose, culminating in an attenuated second peak. Based on 90% CIs, total systemic exposure to MPH-MLR 80 mg capsule/sprinkles was similar to that for Ritalin IR 25 mg three times daily, but marked differences in Cmax values indicated that MPH-MLR regimens were not bioequivalent to Ritalin. MPH Cmax and total systemic exposure over the first 4 hours postdose with MPH-MLR capsule/sprinkles was markedly higher than that associated with the first dose of Ritalin. All study drugs were safe and well tolerated. The PK modeling in adults suggested that differences in MPH pharmacokinetics between MPH-MLR and Ritalin are the result of dosage form design attributes and the associated absorption profiles of MPH.

CONCLUSIONS

MPH-MLR 80 mg provides a long-acting biphasic pattern of plasma MPH concentrations with one less peak and trough than Ritalin IR.

A systematic review of the safety of lisdexamfetamine dimesylate

BACKGROUND

Here we review the safety and tolerability profile of lisdexamfetamine dimesylate (LDX), the first long-acting prodrug stimulant for the treatment of attention-deficit/hyperactivity disorder (ADHD).

METHODS

A PubMed search was conducted for English-language articles published up to 16 September 2013 using the following search terms: (lisdexamfetamine OR lisdexamphetamine OR SPD489 OR Vyvanse OR Venvanse OR NRP104 NOT review [publication type]).

RESULTS

In short-term, parallel-group, placebo-controlled, phase III trials, treatment-emergent adverse events (TEAEs) in children, adolescents, and adults receiving LDX were typical for those reported for stimulants in general. Decreased appetite was reported by 25-39 % of patients and insomnia by 11-19 %. The most frequently reported TEAEs in long-term studies were similar to those reported in the short-term trials. Most TEAEs were mild or moderate in severity. Literature relating to four specific safety concerns associated with stimulant medications was evaluated in detail in patients receiving LDX. Gains in weight, height, and body mass index were smaller in children and adolescents receiving LDX than in placebo controls or untreated norms. Insomnia was a frequently reported TEAE in patients with ADHD of all ages receiving LDX, although the available data indicated no overall worsening of sleep quality in adults. Post-marketing survey data suggest that the rate of non-medical use of LDX was lower than that for short-acting stimulants and lower than or equivalent to long-acting stimulant formulations. Small mean increases were seen in blood pressure and pulse rate in patients receiving LDX.

CONCLUSIONS

The safety and tolerability profile of LDX in individuals with ADHD is similar to that of other stimulants.

Comparison of therapy augmentation and deviation rates from the recommended once-daily dosing regimen between LDX and commonly prescribed long-acting stimulants for the treatment of ADHD in youth and adults

OBJECTIVE

To compare therapy augmentation and deviation rates from the recommended once-daily dosing regimen in Attention Deficit Hyperactivity Disorder (ADHD) patients initiated on lisdexamfetamine (LDX) vs other once-daily Food and Drug Administration (FDA) approved stimulants.

METHODS

ADHD patients initiated on a long-acting ADHD stimulant medication (index medication) in/after 2007 were selected from a large U.S. administrative claims database. Patients were required to be persistent for ≥90 days and continuously enrolled in their healthcare plan for ≥12 months following treatment initiation date. Based on age and previous treatment status, patients were classified into treatment-naïve children and adolescents (6-17 years old), previously treated children and adolescents, treatment-naïve adults (≥18 years old), and previously treated adults. Furthermore, patients were classified into four mutually exclusive treatment groups, based on index medication: lisdexamfetamine (LDX), osmotic release methylphenidate hydrochloride long-acting (OROS MPH), other methylphenidate/dexmethylphenidate long-acting (MPH LA), and amphetamine/dextroamphetamine long-acting (AMPH LA). The average daily consumption was measured as the quantity of index medication supplied in the 12-month study period divided by the total number of days of supply. Therapy augmentation was defined as the use of another ADHD medication concomitantly with the index medication for ≥28 consecutive days. Therapy augmentation and deviation rates from the recommended once-daily dosing regimen were compared between treatment groups using multivariate logistic regression models.

RESULTS

Compared to the other treatment groups, LDX patients were less likely to augment with another ADHD medication (range odds ratios [OR]; 1.28-3.30) and to deviate from the recommended once-daily dosing regimen (range OR; 1.73-4.55), except for previously treated adult patients, where therapy augmentation differences were not statistically significant when compared to OROS MPH and MPH LA patients.

LIMITATION

This study did not control for ADHD severity.

CONCLUSION

Overall, compared to LDX-treated patients, patients initiated on other ADHD medications were equally or more likely to have a therapy augmentation and more likely to deviate from the recommended once-daily dosing regimen.

An observational study of response heterogeneity in children with attention deficit hyperactivity disorder following treatment switch to modified-release methylphenidate

BACKGROUND

Methylphenidate (MPH) has been shown to be effective in the treatment of attention deficit hyperactivity disorder (ADHD) in children. The overall population of children and adolescents with ADHD may comprise distinct clusters of patients that differ in response to MPH. The aim of this analysis was to look for subgroups with different treatment trajectories and to identify their distinctive features.

METHODS

OBSEER was a prospective, observational study examining the effectiveness and safety of once-daily modified-release MPH over 3 months in patients (aged 6-17 years) with ADHD under routine care. Assessments were carried out at baseline (Visit 1), after 1-3 weeks (Visit 2) and 6-12 weeks (Visit 3) after first use of once-daily modified-release MPH. Change in ADHD symptoms, as rated by parents and teachers, was examined post hoc in patients of the intent-to-treat-population (N = 822), using growth-mixture modelling to detect response trajectory groups after switching medication. Age, MPH dose at Visit 1 before medication switch, prescribed once-daily modified-release MPH dose at Visits 1 and 2, conduct problems and emotional symptoms were considered predictors of response subgroups.

RESULTS

Assessing formal statistical criteria and usefulness of the models, a 4-class solution best fitted the data: after switching medication two response groups with severe symptoms at study start and subsequent substantial treatment effects, and two showing no or comparatively little treatment effect, one of which had severe and the other less severe symptoms at study start. Patient age, conduct problems and MPH dose at Visit 1 were predictors of inclusion in subgroups.

CONCLUSIONS

Older children and children with few conduct problems were more likely to be members of a patient cluster with fewer symptoms at study start. Children with a low MPH dose before medication switch had a higher chance of being in the patient cluster with a strong treatment response after switching medication. The current analyses should assist in identifying children likely to achieve a favourable treatment course with MPH and, additionally, those who are in need of alternative treatment options.

Long-acting stimulants for treatment of attention-deficit/hyperactivity disorder: a focus on extended-release formulations and the prodrug lisdexamfetamine dimesylate to address continuing clinical challenges

Individuals with attention-deficit/hyperactivity disorder (ADHD) show pervasive impairments across family, peer, and school or work functioning that may extend throughout the day. Psychostimulants are highly effective medications for the treatment of ADHD, and the development of long-acting stimulant formulations has greatly expanded the treatment options for individuals with ADHD. Strategies for the formulation of long-acting stimulants include the combination of immediate-release and delayed-release beads, and an osmotic-release oral system. A recent development is the availability of the first prodrug stimulant, lisdexamfetamine dimesylate (LDX). LDX itself is inactive but is cleaved enzymatically, primarily in the bloodstream, to release d-amphetamine (d-AMP). Several clinical trials have demonstrated that long-acting stimulants are effective in reducing ADHD symptoms compared with placebo. Analog classroom and simulated adult workplace environment studies have shown that long-acting stimulants produce symptom reduction for at least 12 h. Long-acting stimulants exhibit similar tolerability and safety profiles to short-acting equivalents. While variations in gastric pH and motility can alter the availability and absorption of stimulants released from long-acting formulations, the systemic exposure to d-AMP following LDX administration is unlikely to be affected by gastrointestinal conditions. Long-acting formulations may also improve adherence and lower abuse potential compared with their short-acting counterparts. The development of long-acting stimulants provides physicians with an increased range of medication options to help tailor treatment for individuals with ADHD.

A post hoc comparison of the effects of lisdexamfetamine dimesylate and osmotic-release oral system methylphenidate on symptoms of attention-deficit hyperactivity disorder in children and adolescents

INTRODUCTION

There are limited head-to-head data comparing the efficacy of long-acting amfetamine- and methylphenidate-based psychostimulants as treatments for individuals with attention-deficit hyperactivity disorder (ADHD). This post hoc analysis provides the first parallel-group comparison of the effect of lisdexamfetamine dimesylate (lisdexamfetamine) and osmotic-release oral system methylphenidate (OROS-MPH) on symptoms of ADHD in children and adolescents.

STUDY DESIGN

This was a post hoc analysis of a randomized, double-blind, parallel-group, dose-optimized, placebo-controlled, phase III study.

SETTING

The phase III study was carried out in 48 centres across ten European countries.

PATIENTS

The phase III study enrolled children and adolescents (aged 6-17 years) who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision criteria for a primary diagnosis of ADHD and who had a baseline ADHD Rating Scale IV (ADHD-RS-IV) total score of 28 or higher.

INTERVENTION

Eligible patients were randomized (1:1:1) to receive a once-daily, optimized dose of lisdexamfetamine (30, 50 or 70 mg/day), placebo or OROS-MPH (18, 36 or 54 mg/day) for 7 weeks.

MAIN OUTCOME MEASURES

In this post hoc analysis, efficacy was assessed using the ADHD-RS-IV and Clinical Global Impressions-Improvement (CGI-I) scale. Responders were defined as those achieving at least a 30% reduction from baseline in ADHD-RS-IV total score and a CGI-I score of 1 (very much improved) or 2 (much improved). The proportion of patients achieving an ADHD-RS-IV total score less than or equal to the mean for their age (based on normative data) was also determined. Endpoint was the last on-treatment visit with a valid assessment. Safety assessments included treatment-emergent adverse events (TEAEs) and vital signs.

RESULTS

Of the 336 patients randomized, 332 were included in the safety population, 317 were included in the full analysis set and 196 completed the study. The mean (standard deviation) ADHD-RS-IV total score at baseline was 40.7 (7.31) for lisdexamfetamine, 41.0 (7.14) for placebo and 40.5 (6.72) for OROS-MPH. The least-squares (LS) mean change (standard error) in ADHD-RS-IV total score from baseline to endpoint was -24.3 (1.16) for lisdexamfetamine, -5.7 (1.13) for placebo and -18.7 (1.14) for OROS-MPH. The difference between lisdexamfetamine and OROS-MPH in LS mean change (95% confidence interval [CI]) in ADHD-RS-IV total score from baseline to endpoint was statistically significant in favour of lisdexamfetamine (-5.6 [-8.4 to -2.7]; p < 0.001). The difference between lisdexamfetamine and OROS-MPH in the percentage of patients (95% CI) with a CGI-I score of 1 or 2 at endpoint was 17.4 (5.0-29.8; p < 0.05; number needed to treat [NNT] 6), and the difference in the percentage of patients (95% CI) achieving at least a 30% reduction in ADHD-RS-IV total score and a CGI-I score of 1 or 2 was 18.3 (5.4-31.3; p < 0.05; NNT 6). The difference between lisdexamfetamine and OROS-MPH in the percentage of patients (95% CI) with an ADHD-RS-IV total score less than or equal to the mean for their age at endpoint was 14.0 (0.6-27.4; p = 0.050). The overall frequency of TEAEs and the frequencies of decreased appetite, insomnia, decreased weight, nausea and anorexia TEAEs were greater in patients treated with lisdexamfetamine than in those treated with OROS-MPH, whereas headache and nasopharyngitis were more frequently reported in patients receiving OROS-MPH.

CONCLUSIONS

This post hoc analysis showed that, at the doses tested, patients treated with lisdexamfetamine showed statistically significantly greater improvement in symptoms of ADHD than those receiving OROS-MPH, as assessed using the ADHD-RS-IV and CGI-I. The safety profiles of lisdexamfetamine and OROS-MPH were consistent with the known effects of stimulant medications.

Treating attention-deficit/hyperactivity disorder in adults: focus on once-daily medications

OBJECTIVE

To review the efficacy, safety, and abuse liability of approved treatments in adults with attention-deficit/hyperactivity disorder (ADHD), with a focus on once-daily medications.

DATA SOURCES

PubMed was searched for relevant studies/reviews in English from 2002 to 2011 on adult ADHD treatments.

STUDY SELECTION

Keywords used in the search were ADHD, adults, and treatment. Limits included only clinical trials, meta-analyses, randomized controlled trials, and reviews including adults (aged ≥ 19 years).

DATA EXTRACTION

Selection criteria returned 471 publications. Retrieved studies were excluded if they primarily focused on children, treatments not indicated for ADHD, or ADHD and comorbid conditions.

DATA SYNTHESIS

An epidemiologic survey revealed that 10.9% of adults identified with ADHD had received treatment during the prior 12 months. Treatments for ADHD in adults include pharmacologic and nonpharmacologic options. US Food and Drug Administration-approved long-acting stimulants and a nonstimulant with proven efficacy and safety profiles have been developed and include osmotic-release oral system methylphenidate hydrochloride (OROS-methylphenidate), extended-release dexmethylphenidate hydrochloride, mixed amphetamine salts extended release (MAS-XR), the nonstimulant atomoxetine hydrochloride, and the prodrug lisdexamfetamine dimesylate. Long-acting stimulants differ in formulation characteristics used to achieve extended release, with OROS-methylphenidate employing an osmotic-release technology, extended-release dexmethylphenidate hydrochloride and MAS-XR using pH-dependent beads, and lisdexamfetamine dimesylate using prodrug technology. These features variably affect pharmacokinetic characteristics, duration of action, and abuse liability. While all long-acting medications have varied pharmacokinetic features, mechanism of action, and duration of effect, all are generally efficacious and safety profiles are similar.

CONCLUSION

Approved long-acting treatments in adults with ADHD were effective in improving symptoms and were generally well tolerated.

Psychostimulant treatment of cocaine dependence

The use of stimulant medications for the treatment of cocaine dependence is an evolving scientific line of research. To date, the most promising results are with the higher-potency medications, the amphetamine analogues, or a combination of a dopaminergic medication with a contingency management behavioral intervention. The development of effective pharmacotherapies for opioid and nicotine dependence using an agonist replacement approach suggests that these promising findings needs to continue to be vigorously investigated. In clinical trial reports, there are very few instances of cardiovascular adverse events, which suggests that for well-selected patients with cocaine dependence, stimulant replacement therapy can be safe. However, clinical trial eligibility criteria excludes most high-risk patients from participating, and introducing stimulant substitution to the wider treatment community would likely expose more vulnerable patients to the medical risks associated with stimulant treatment while using cocaine. As treatment development research moves forward, attention must be paid to helping clinicians select patients who are most likely to benefit from stimulant substitution treatment and how to identify those at risk. An additional concern with the use of stimulant medication treatment of cocaine dependence is prescribing controlled substances for patients with active substance use disorders. Again, within a clinical trial, medication supplies are monitored and distributed carefully in small quantities. In a community setting, misuse or diversion will be risks associated with prescribing controlled substances to patients with addictive disorders, but therapeutic strategies for monitoring and limiting that risk can be implemented. Psychostimulant pharmacotherapy is a promising line of research for the treatment of cocaine dependence, a condition for which no effective pharmacotherapy has been identified. Further research is required to confirm positive results from single-site trials, in particular the study of amphetamines as a treatment for cocaine dependence. As this literature evolves, strategies to manage the risk of prescribing controlled substances to patients with addictive disorders need to be tested and refined. Biases against using controlled substances as a treatment for cocaine dependence should be challenged, much in the way the use of agonist treatment transformed the treatment of opioid dependence despite initial resistance from the field.

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

Attention-deficit/hyperactivity disorder is one of the most common neurobehavioral disorders defined by developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. Symptoms begin in childhood and may persist into adolescence and adulthood. Currently available pharmacological treatment options for attention-deficit/hyperactivity disorder in children and adolescents include stimulants that are efficacious and well tolerated; however, many of these preparations require multiple daily dosing and have the potential for abuse. Lisdexamfetamine dimesylate, the first prodrug stimulant, was developed to provide a longer duration of effect. It demonstrates a predictable delivery of the active drug, d-amphetamine, with low interpatient variability, and has a reduced potential for abuse. A literature search of the MEDLINE database and clinical trials register from 1995-2011, as well as relevant abstracts presented at annual professional meetings, on lisdexamfetamine dimesylate in children and adolescents were included for review. This article presents the pharmacokinetic profile, efficacy, and safety of lisdexamfetamine dimesylate for the treatment of attention-deficit/hyperactivity disorder in children and, more recently, in adolescents.