Relative Bioavailability of Lisdexamfetamine 70-mg Capsules in Fasted and Fed Healthy Adult Volunteers and in Solution: A Single-Dose, Crossover Pharmacokinetic Study

Comparative pharmacology and abuse potential of oral dexamphetamine and lisdexamfetamine-A literature review

OBJECTIVE

To compare the pharmacology and abuse potential of oral dexamphetamine and lisdexamfetamine (LDX).

METHODS

A search of Medline and Embase was conducted to identify relevant articles for this literature review.

RESULTS

Dexamphetamine and LDX, a prodrug of dexamphetamine, are indicated for the treatment of attention-deficit/hyperactivity disorder. It has been suggested that LDX may have a reduced potential for oral abuse compared to immediate-release dexamphetamine. As a prodrug, LDX has the same pharmacodynamic properties as dexamphetamine. A study in healthy adults showed that the pharmacokinetic profile of dexamphetamine following oral administration of LDX is essentially identical to that of an equimolar dose of dexamphetamine administered 1 h later. In addition, dexamphetamine produced subjective drug liking effects comparable to those produced by LDX. LDX showed linear dose proportional pharmacokinetics up to a dose of 250 mg, indicating a lack of overdose protection at supratherapeutic doses. Furthermore, the exposure to dexamphetamine released from LDX may be prolonged by the consumption of alkalizing agents.

CONCLUSIONS

The available evidence from pharmacodynamic, pharmacokinetic and abuse liability studies suggests a comparable potential for oral abuse of dexamphetamine and LDX.

Cobalt-catalyzed amination of aziridines and azetidines toward 1,2- and 1,3-diamines

Diamines play important roles in synthetic organic chemistry and thus facilitate life and materials sciences. Herein we report a cobalt-catalyzed ring opening, nucleophilic amination of aziridines and azetidines with N-fluorosulfonamides toward a wide range of 1,2- and 1,3-diamine derivatives in moderate to good yields under mild conditions.

In silico evaluation of the role of lisdexamfetamine on attention-deficit/hyperactivity disorder common psychiatric comorbidities: mechanistic insights on binge eating disorder and depression

Attention-deficit/hyperactivity disorder (ADHD) is a psychiatric condition well recognized in the pediatric population that can persist into adulthood. The vast majority of patients with ADHD present psychiatric comorbidities that have been suggested to share, to some extent, the pathophysiological mechanism of ADHD. Lisdexamfetamine (LDX) is a stimulant prodrug approved for treating ADHD and, in the US, also for binge eating disorder (BED). Herein, we evaluated, through a systems biology-based in silico method, the efficacy of a virtual model of LDX (vLDX) as ADHD treatment to improve five common ADHD psychiatric comorbidities in adults and children, and we explored the molecular mechanisms behind LDX's predicted efficacy. After the molecular characterization of vLDX and the comorbidities (anxiety, BED, bipolar disorder, depression, and tics disorder), we created a protein-protein interaction human network to which we applied artificial neural networks (ANN) algorithms. We also generated virtual populations of adults and children-adolescents totaling 2,600 individuals and obtained the predicted protein activity from Therapeutic Performance Mapping System models. The latter showed that ADHD molecular description shared 53% of its protein effectors with at least one studied psychiatric comorbidity. According to the ANN analysis, proteins targeted by vLDX are predicted to have a high probability of being related to BED and depression. In BED, vLDX was modeled to act upon neurotransmission and neuroplasticity regulators, and, in depression, vLDX regulated the hypothalamic-pituitary-adrenal axis, neuroinflammation, oxidative stress, and glutamatergic excitotoxicity. In conclusion, our modeling results, despite their limitations and although requiring in vitro or in vivo validation, could supplement the design of preclinical and potentially clinical studies that investigate treatment for patients with ADHD with psychiatric comorbidities, especially from a molecular point of view.

In silico clinical trial evaluating lisdexamfetamine's and methylphenidate's mechanism of action computational models in an attention-deficit/hyperactivity disorder virtual patients' population

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is an impairing psychiatric condition with the stimulants, lisdexamfetamine (LDX), and methylphenidate (MPH), as the first lines pharmacological treatment.

Methods

Herein, we applied a novel in silico method to evaluate virtual LDX (vLDX) and vMPH as treatments for ADHD applying quantitative systems pharmacology (QSP) models. The objectives were to evaluate the model's output, considering the model characteristics and the information used to build them, to compare both virtual drugs' efficacy mechanisms, and to assess how demographic (age, body mass index, and sex) and clinical characteristics may affect vLDX's and vMPH's relative efficacies.

Results and Discussion

We molecularly characterized the drugs and pathologies based on a bibliographic search, and generated virtual populations of adults and children-adolescents totaling 2,600 individuals. For each virtual patient and virtual drug, we created physiologically based pharmacokinetic and QSP models applying the systems biology-based Therapeutic Performance Mapping System technology. The resulting models' predicted protein activity indicated that both virtual drugs modulated ADHD through similar mechanisms, albeit with some differences. vMPH induced several general synaptic, neurotransmitter, and nerve impulse-related processes, whereas vLDX seemed to modulate neural processes more specific to ADHD, such as GABAergic inhibitory synapses and regulation of the reward system. While both drugs' models were linked to an effect over neuroinflammation and altered neural viability, vLDX had a significant impact on neurotransmitter imbalance and vMPH on circadian system deregulation. Among demographic characteristics, age and body mass index affected the efficacy of both virtual treatments, although the effect was more marked for vLDX. Regarding comorbidities, only depression negatively impacted both virtual drugs' efficacy mechanisms and, while that of vLDX were more affected by the co-treatment of tic disorders, the efficacy mechanisms of vMPH were disturbed by wide-spectrum psychiatric drugs. Our in silico results suggested that both drugs could have similar efficacy mechanisms as ADHD treatment in adult and pediatric populations and allowed raising hypotheses for their differential impact in specific patient groups, although these results require prospective validation for clinical translatability.

Pharmacokinetics of a Modified-Release Dexamphetamine Sulfate Formulation Following Single and Multiple Dosing in Healthy Adults: Comparative Bioavailability with Immediate-Release Dexamphetamine Sulfate, between Strengths, Assessment of Food and Meal Composition Effects

Background

A modified-release dexamphetamine sulfate formulation (DEX-MR) is under development for the treatment of attention-deficit/hyperactivity disorder.

Objective

We investigated the bioequivalence of once-daily DEX-MR to twice-daily immediate-release dexamphetamine sulfate (DEX-IR) after single and multiple dosing and between strengths, and effects of food and meal types.

Method

Three randomized, open-label, crossover studies in healthy males were conducted. In the single-dose study, participants received DEX-MR 20 mg, DEX-MR 10 mg (20 mg dose), and twice-daily DEX-IR 10 mg under fasted conditions and after a high-fat, high-calorie breakfast. In the breakfast study, participants received DEX-MR 20 mg and twice-daily DEX-IR 10 mg after a normocaloric and a high-fat, high-calorie breakfast. In the multiple-dose study, participants received DEX-MR 20 mg and twice-daily DEX-IR 10 mg for seven days each. In the run-in period (five days), participants consumed a normocaloric breakfast; on profile days, participants consumed a normocaloric breakfast (day 6) or a high-fat, high-calorie breakfast (day 7).

Results

Once-daily DEX-MR at a dose of 20 mg was bioequivalent to twice-daily DEX-IR 10 mg after single dosing under fasted and fed conditions and after multiple dosing under fed conditions. DEX-MR 10 mg and DEX-MR 20 mg were bioequivalent when administered as a single 20 mg dose. Food slightly reduced the rate and extent of absorption of DEX-MR and delayed the time to peak plasma concentration (tmax) by approximately two hours compared to the fasted state. Bioavailability of DEX-MR was comparable under different meal conditions (normocaloric vs. high-fat, high-calorie breakfast) both after single and multiple dosing.

Conclusions

Bioequivalence of once-daily DEX-MR and twice-daily DEX-IR was established. 1×2 DEX-MR 10 mg was bioequivalent to 1×1 DEX-MR 20 mg. DEX-MR should be administered with/after a meal to achieve the targeted pharmacokinetic profile (delayed tmax). Bioavailability of DEX-MR is not affected by meal composition (i.e., fat and caloric content).

Nanowired Delivery of Mesenchymal Stem Cells with Antioxidant Compound H-290/51 Reduces Exacerbation of Methamphetamine Neurotoxicity in Hot Environment

Military personnel are often exposed to hot environments either for combat operations or peacekeeping missions. Hot environment is a severe stressful situation leading to profound hyperthermia, fatigue and neurological impairments. To avoid stressful environment, some people frequently use methamphetamine (METH) or other psychostimulants to feel comfortable under adverse situations. Our studies show that heat stress alone induces breakdown of the blood-brain barrier (BBB) and edema formation associated with reduced cerebral blood flow (CBF). On the other hand, METH alone induces hyperthermia and neurotoxicity. These effects of METH are exacerbated at high ambient temperatures as seen with greater breakdown of the BBB and brain pathology. Thus, a combination of METH use at hot environment may further enhance the brain damage-associated behavioral dysfunctions. METH is well known to induce severe oxidative stress leading to brain pathology. In this investigation, METH intoxication at hot environment was examined on brain pathology and to explore suitable strategies to induce neuroprotection. Accordingly, TiO₂-nanowired delivery of H-290/51 (150 mg/kg, i.p.), a potent chain-breaking antioxidant in combination with mesenchymal stem cells (MSCs), is investigated in attenuating METH-induced brain damage at hot environment in model experiments. Our results show that nanodelivery of H-290/51 with MSCs significantly enhanced CBF and reduced BBB breakdown, edema formation and brain pathology following METH exposure at hot environment. These observations are the first to point out that METH exacerbated brain pathology at hot environment probably due to enhanced oxidative stress, and MSCs attenuate these adverse effects, not reported earlier.

Methods to Develop an in silico Clinical Trial: Computational Head-to-Head Comparison of Lisdexamfetamine and Methylphenidate

Regulatory agencies encourage computer modeling and simulation to reduce the time and cost of clinical trials. Although still not classified in formal guidelines, system biology-based models represent a powerful tool for generating hypotheses with great molecular detail. Herein, we have applied a mechanistic head-to-head in silico clinical trial (ISCT) between two treatments for attention-deficit/hyperactivity disorder, to wit lisdexamfetamine (LDX) and methylphenidate (MPH). The ISCT was generated through three phases comprising (i) the molecular characterization of drugs and pathologies, (ii) the generation of adult and children virtual populations (vPOPs) totaling 2,600 individuals and the creation of physiologically based pharmacokinetic (PBPK) and quantitative systems pharmacology (QSP) models, and (iii) data analysis with artificial intelligence methods. The characteristics of our vPOPs were in close agreement with real reference populations extracted from clinical trials, as did our PBPK models with in vivo parameters. The mechanisms of action of LDX and MPH were obtained from QSP models combining PBPK modeling of dosing schemes and systems biology-based modeling technology, i.e., therapeutic performance mapping system. The step-by-step process described here to undertake a head-to-head ISCT would allow obtaining mechanistic conclusions that could be extrapolated or used for predictions to a certain extent at the clinical level. Altogether, these computational techniques are proven an excellent tool for hypothesis-generation and would help reach a personalized medicine.

Lisdexamfetamine and amphetamine pharmacokinetics in oral fluid, plasma, and urine after controlled oral administration of lisdexamfetamine

Lisdexamfetamine (LDX) is a long-acting prodrug stimulant indicated for the treatment of attention-deficit/hyperactivity disorder (ADHD) and binge-eating disorder (BED) symptoms. In vivo hydrolysis of the LDX amide bond releases the therapeutically active d-amphetamine (d-AMPH). This study aims to describe the pharmacokinetics of LDX and its major metabolite d-AMPH in human oral fluid, urine and plasma after a single 70 mg oral dose of LDX dimesylate. Six volunteers participated in the study. Oral fluid and blood samples were collected for up to 72 h and urine for up to 120 h post-drug administration for the pharmacokinetic evaluation of intact LDX and d-AMPH. Samples were analyzed by LC-MS/MS. Regarding noncompartmental analysis, d-AMPH reached the maximum concentration at 3.8 and 4 h post-administration in plasma and oral fluid, respectively, with a mean peak concentration value almost six-fold higher in oral fluid. LDX reached maximum concentration at 1.2 and 1.8 h post-administration in plasma and oral fluid, respectively, with a mean peak concentration value almost three-fold higher in plasma. Intact LDX and d-AMPH were detected in the three matrices. The best fit of compartmental analysis was found in the one-compartment model for both analytes in plasma and oral fluid. There was a correlation between oral fluid and plasma d-AMPH concentrations and between parent to metabolite concentration ratios over time in plasma as well as in oral fluid.

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.

Effects of Food on the Bioavailability of Amphetamine in Healthy Adults After Administration of SHP465 Mixed Amphetamine Salts Extended-Release Capsules

Background and objective

SHP465 mixed amphetamine salts extended release is a once-daily, single-entity, mixed amphetamine salts capsule product for attention-deficit/hyperactivity disorder. The objective of this study was to evaluate amphetamine pharmacokinetics following SHP465 mixed amphetamine salts under three administration conditions.

Methods

Healthy adults (n = 16) enrolled in an open-label, randomized, three-period crossover study with three single-dose 50-mg SHP465 mixed amphetamine salts treatments (fasting ≥ 10 h before administration [reference]; high-fat meal consumption 30 min before administration; sprinkling capsule contents on applesauce) separated by ≥ 7-day washouts. Blood samples for evaluating d- and l-amphetamine pharmacokinetics were collected pre-dose and up to 60 h post-dose. Assessments included maximum plasma concentration, time to maximum plasma concentration, and area under the plasma concentration–time curve from 0 to infinity. Exponentiated least-squares mean ratios with 90% confidence intervals for test treatments relative to the reference treatment were calculated, with the absence of an effect indicated by the 90% confidence intervals falling within the 80–125% range.

Results

Least-squares mean (90% confidence interval) ratios for maximum plasma concentration and area under the plasma concentration–time curve from 0 to infinity indicated neither consuming a high-fat meal (d-amphetamine: 85.33 [80.44, 90.50] and 91.11 [86.69, 95.75], respectively; l-amphetamine: 85.22 [80.18, 90.59] and 88.74 [83.89, 93.87]) nor sprinkling the capsule contents on applesauce (d-amphetamine: 95.76 [90.28, 101.57] and 95.77 [91.13, 100.65]; l-amphetamine: 96.90 [91.16, 103.00] and 94.78 [89.60, 100.26]) altered amphetamine exposure. Consuming a high-fat meal prolonged median time to maximum plasma concentration for d- and l-amphetamine by 5.0 and 4.5 h, respectively, relative to reference treatment.

Conclusions

These findings demonstrate SHP465 mixed amphetamine salts capsules can be swallowed whole with or without food or the capsule contents can be sprinkled on applesauce.

Relative Bioavailabilities of Lisdexamfetamine Dimesylate and D-Amphetamine in Healthy Adults in an Open-Label, Randomized, Crossover Study After Mixing Lisdexamfetamine Dimesylate With Food or Drink

Supplemental Digital Content is Available in the Text.

Background:

This open-label, crossover study examined lisdexamfetamine dimesylate (LDX) and d-amphetamine pharmacokinetics in healthy adults after administration of an intact LDX capsule or after the capsule was emptied into orange juice or yogurt and the contents consumed.

Methods:

Healthy adult volunteers (N = 30) were administered a 70-mg LDX capsule or the contents of a 70-mg capsule mixed with yogurt or orange juice using a 3-way crossover design. Blood samples were collected serially for up to 96 hours after dose. Pharmacokinetic endpoints included maximum plasma concentration (C_max) and area under the plasma concentration versus time curve from zero to infinity (AUC_0–∞) or to last assessment (AUC_last). Relative LDX and d-amphetamine bioavailabilities from the contents of a 70-mg LDX capsule mixed with orange juice or yogurt were compared with those from the intact LDX capsule using bioequivalence-testing procedures.

Results:

Geometric least squares mean ratios (90% confidence intervals [CIs]) for d-amphetamine (active moiety) were within the prespecified bioequivalence range (0.80–1.25) when the contents of a 70-mg LDX capsule were mixed with orange juice [C_max: 0.971 (0.945, 0.998); AUC_0–∞: 0.986 (0.955, 1.019); AUC_last: 0.970 (0.937, 1.004)] or yogurt [C_max: 0.970 (0.944, 0.997); AUC_0–∞: 0.945 (0.915, 0.976); AUC_last: 0.944 (0.912, 0.977)]. Geometric least squares mean ratios (90% CIs) for LDX (inactive prodrug) were below the accepted range when the contents of a 70-mg LDX capsule were mixed with orange juice [C_max: 0.641 (0.582, 0.707); AUC_0–∞: 0.716 (0.647, 0.792); AUC_last: 0.708 (0.655, 0.766)]; the lower 90% CI for C_max [0.828 (0.752, 0.912)] was below the accepted range when the contents of a 70-mg LDX capsule were mixed with yogurt.

Conclusions:

Relative bioavailability of d-amphetamine (the active moiety) did not differ across administrations, which suggests that emptying an LDX capsule into orange juice or yogurt and consuming it is an alternative to intact capsules.

A Single-Dose, Open-Label Study of the Pharmacokinetics, Safety, and Tolerability of Lisdexamfetamine Dimesylate in Individuals With Normal and Impaired Renal Function

BACKGROUND

Lisdexamfetamine (LDX) and D-amphetamine pharmacokinetics were assessed in individuals with normal and impaired renal function after a single LDX dose; LDX and D-amphetamine dialyzability was also examined.

METHODS

Adults (N = 40; 8/group) were enrolled in 1 of 5 renal function groups [normal function, mild impairment, moderate impairment, severe impairment/end-stage renal disease (ESRD) not requiring hemodialysis, and ESRD requiring hemodialysis] as estimated by glomerular filtration rate (GFR). Participants with normal and mild to severe renal impairment received 30 mg LDX; blood samples were collected predose and serially for 96 hours. Participants with ESRD requiring hemodialysis received 30 mg LDX predialysis and postdialysis separated by a washout period of 7-14 days. Predialysis blood samples were collected predose, serially for 72 hours, and from the dialyzer during hemodialysis; postdialysis blood samples were collected predose and serially for 48 hours. Pharmacokinetic end points included maximum plasma concentration (Cmax) and area under the plasma concentration versus time curve from time 0 to infinity (AUC0-∞) or to last assessment (AUClast).

RESULTS

Mean LDX Cmax, AUClast, and AUC0-∞ in participants with mild to severe renal impairment did not differ from those with normal renal function; participants with ESRD had higher mean Cmax and AUClast than those with normal renal function. D-amphetamine exposure (AUClast and AUC0-∞) increased and Cmax decreased as renal impairment increased. Almost no LDX and little D-amphetamine were recovered in the dialyzate.

CONCLUSIONS

There seems to be prolonged D-amphetamine exposure after 30 mg LDX as renal impairment increases. In individuals with severe renal impairment (GFR: 15 ≤ 30 mL·min·1.73 m), the maximum LDX dose is 50 mg/d; in patients with ESRD (GFR: <15 mL·min·1.73 m), the maximum LDX dose is 30 mg/d. Neither LDX nor D-amphetamine is dialyzable.

The Clinical Pharmacokinetics of Amphetamines Utilized in the Treatment of Attention-Deficit/Hyperactivity Disorder

Amphetamine (AMP), an indirectly acting psychostimulant approved for the treatment of attention-deficit/hyperactivity disorder (ADHD) in children, adolescents, and adults, is among the most long-standing therapeutic agents in all of clinical psychopharmacology. This review focuses on AMP absorption, metabolism, and elimination brought to bear on comparative pharmacokinetics in its various formulations. A comprehensive search of the published literature was conducted using MEDLINE (PubMed) and Google Scholar databases through April 2017 to retrieve all pertinent in vitro and human studies for review and synthesis. Additionally, Food and Drug Administration (FDA) databases were accessed for otherwise unavailable data when possible. Initially available as racemic (dl)-AMP, this drug was later supplanted by enantiopure (d)-AMPH or enantioenriched (75:25 dl)-AMP formulations; although racemic AMP returned as an approved drug to treat ADHD in 2014. Presently, there are several immediate-release (IR) formulations available, including d-AMP, dl-AMP, and mixed amphetamine salts, which are neither racemic nor the pure d-enantiomer (i.e., a 3:1 mixture of d-AMP and l-AMP). Furthermore, new modified-release AMP formulations, including an oral suspension and an orally disintegrating tablet, are now available. A lysine-bonded prodrug form of d-AMP also serves as a treatment option. Oral AMP is rapidly absorbed, with high absolute bioavailability, followed by extensive metabolism involving multiple enzymes. Some metabolic pathways exhibit stereoselective biotransformations favoring the l-isomer substrate. Drug exposure exhibits dose-proportional pharmacokinetics. Body weight is a fundamental determinant of differences in observed AMP plasma concentrations. IR formulations typically provide a T_max from 2 to 3 hours. In replicated studies, children exhibit a shorter plasma T_1/2 (∼7 hours) relative to adults (∼10 to 12 hours). There are few documented pharmacokinetic drug interactions of clinical significance beyond influences of drug-induced alteration of urinary pH. The array of AMP formulations addressed in this review offer flexibility in dosing, drug onset, and offset to assist in individualized pharmacotherapy of ADHD.

Pharmacokinetics and Pharmacodynamics of Lisdexamfetamine Compared with D-Amphetamine in Healthy Subjects

Rationale: Lisdexamfetamine is a prodrug of D-amphetamine used for the treatment of attention-deficit/hyperactivity disorder (ADHD). Lisdexamfetamine is thought to have a prolonged pharmacokinetic profile compared with oral D-amphetamine, possibly associated with lower drug liking and a lower risk of oral misuse. However, differences in the pharmacokinetics and pharmacodynamics of lisdexamfetamine and D-amphetamine have not been directly compared. Methods: Equimolar doses of D-amphetamine (40 mg) and lisdexamfetamine (100 mg), and placebo were administered in 24 healthy subjects in a randomized, double-blind, placebo-controlled, cross-over study. Plasma concentrations of amphetamine, subjective effects, and vital signs were repeatedly assessed. The pharmacokinetic parameters were determined using compartmental modeling. Results: The increase in plasma concentrations of amphetamine had a 0.6 ± 0.6 h (mean ± SD) longer lag time and reached peak levels 1.1 ± 1.5 h later after lisdexamfetamine administration compared with D-amphetamine administration, but no differences in maximal concentrations or total exposure (AUC) were found between the two treatments. Consistent with the pharmacokinetics, the subjective and cardiovascular stimulant effects of lisdexamfetamine also occurred later compared with D-amphetamine. However, no differences in peak ratings of potentially abuse-related subjective drug effects (e.g., drug liking, drug high, stimulation, happy, well-being, and self-confidence) were observed after lisdexamfetamine administration compared with D-amphetamine administration. Lisdexamfetamine and D-amphetamine also produced similar peak increases in mean arterial blood pressure, heart rate, body temperature, pupil size, and adverse effects. Conclusion: The pharmacokinetics and pharmacodynamics of lisdexamfetamine are similar to D-amphetamine administered 1h later. Lisdexamfetamine is likely associated with a similar risk of oral abuse as D-amphetamine. The study was registered at ClinicalTrials.gov (NCT02668926).

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.

Lisdexamfetamine: A Review in ADHD in Adults

Lisdexamfetamine dimesylate (lisdexamfetamine) is a long-acting amfetamine prodrug with a convenient once-daily oral regimen that offers the potential for improved adherence and reduced abuse compared with short-acting preparations of amfetamines. Lisdexamfetamine (as Elvanse Adult(®); Tyvense Adult™) has been approved for use in adults with attention-deficit hyperactivity disorder (ADHD) under the EU decentralization procedure, with the first approvals in the UK, Sweden and Denmark. This approval reflects the results of three short-term trials in adults with ADHD in which fixed- or flexible-dose lisdexamfetamine produced significantly greater improvements than placebo in ADHD symptoms, overall functioning, executive functioning (including in patients with significant pre-existing impairment) and quality of life. Of note, a post hoc analysis of one of these studies suggested that the response to lisdexamfetamine was generally similar in treatment-naïve patients and those who had already received-and not responded satisfactorily to-previous ADHD therapies, including methylphenidate (MPH). Two further studies demonstrated the longer-term effectiveness of flexible-dose lisdexamfetamine in reducing ADHD symptoms, albeit maintenance of efficacy required ongoing treatment with the drug. Lisdexamfetamine was generally well tolerated in clinical trials, with an adverse event profile typical of that reported for other long-acting stimulants. Head-to-head comparisons with other long-acting agents, notably MPH and atomoxetine, are lacking. Nonetheless, on the basis of the available data, lisdexamfetamine provides a useful alternative option for the treatment of adults with ADHD, including those who have not responded adequately to previous ADHD therapies, including MPH.

Lisdexamfetamine Dimesylate Effects on the Pharmacokinetics of Cytochrome P450 Substrates in Healthy Adults in an Open-Label, Randomized, Crossover Study

INTRODUCTION

This open-label, randomized, two-period drug interaction study assessed lisdexamfetamine dimesylate (LDX) effects on cytochrome P450 (CYP) enzyme (CYP1A2, CYP2D6, CYP2C19, and CYP3A) activity.

METHODS

Thirty healthy volunteers were administered the Cooperstown cocktail (CYP1A2 [caffeine 200 mg], CYP2D6 [dextromethorphan 30 mg], CYP2C19 [omeprazole 40 mg], and CYP3A [midazolam 0.025 mg/kg] substrates) or Cooperstown cocktail + oral LDX 70 mg. Blood samples for pharmacokinetic analysis were collected pre-dose and serially for 72 h post-dose. Treatment differences in the primary endpoints, maximum plasma concentration (C max) and area under the plasma concentration versus time curve from 0 to infinity (AUC0-∞), were assessed using geometric mean ratios with 90 % CIs.

RESULTS

Geometric least squares (LS) means (without versus with LDX) for C max (ng/mL) were 5370 versus 5246 for caffeine, 2.43 versus 2.87 for dextromethorphan, 35.23 versus 35.11 for midazolam, and 677.9 versus 466.9 for omeprazole; and for AUC0-∞ (ng · h/mL) were 56,207 versus 56,688 for caffeine, 34.85 versus 37.27 for dextromethorphan, 92.07 versus 93.04 for midazolam, and 1428 versus 1499 for omeprazole. Geometric LS mean ratios were within the standard bioequivalence testing range, except for omeprazole and dextromethorphan C max. Parent/metabolite C max and AUC0-∞ ratios were similar between treatments except for dextromethorphan/dextrorphan AUC0-∞ ratio, which was lower with LDX. No serious or severe treatment-emergent adverse events were reported.

CONCLUSIONS

LDX did not alter CYP1A2, CYP2D6, or CYP3A activity. A small C max reduction for omeprazole and its metabolite was observed, possibly reflecting an effect either on the activity of CYP2C19 or omeprazole absorption.

Pilot study of the effects of lisdexamfetamine on cocaine use: A randomized, double-blind, placebo-controlled trial

BACKGROUND

Amphetamine analogs have been demonstrated to have some efficacy in reducing use in cocaine dependent individuals. However, these agents also have potential for abuse. Lisdexamfetamine (LDX), a lysine+dextroamphetamine formulation, has been approved for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD) and as a prodrug, has less abuse potential.

OBJECTIVE

This pilot study sought to evaluate the safety, tolerability, and efficacy of LDX as a candidate treatment for cocaine dependence.

METHODS

A randomized, double-blind, placebo-controlled parallel group study served to evaluate LDX in 43 cocaine-dependent individuals: (1) placebo (PBO; 0mg, n=21), (2) LDX (70mg, n=22). Participants received medication for 14 weeks. Cocaine use was determined based on urine analysis for benzoylecgonine (BE; a cocaine metabolite).

RESULTS

Retention rates were higher though not significantly different in the PBO (71.4%) than the LDX condition (57.1%). Compared to those in the PBO condition, those receiving LDX were more likely to report experiencing (ps<0.05) diarrhea (45.5% vs. 14.3%), headaches (45.5% vs. 9.5%), and anxiety (31.8% vs. 4.8%). No differences in medication conditions were observed for blood pressure, heart rate, or body weight. In the randomized sample, no differences in cocaine use were seen. Those receiving LDX reported significantly less craving for cocaine than participants receiving PBO.

CONCLUSIONS

LDX did not significantly reduce cocaine use compared to PBO in the randomized sample.

Lisdexamfetamine for binge eating disorder in adults: a systematic review of the efficacy and safety profile for this newly approved indication - what is the number needed to treat, number needed to harm and likelihood to be helped or harmed?

OBJECTIVE

To describe the efficacy and safety of lisdexamfetamine dimesylate (LDX) for the treatment of binge eating disorder (BED).

DATA SOURCES

The pivotal registration trials were accessed by querying http://www.ncbi.nlm.nih.gov/pubmed/, http://www.clinicaltrials.gov and http://www.clinicaltrialsregister.eu for the search terms 'lisdexamfetamine' and 'binge', and by also querying the Web of Science (Thomson Reuters) and Embase (Elsevier) commercial databases, and by asking the manufacturer for copies of posters presented at congresses. Product labelling provided additional information.

STUDY SELECTION

All available clinical reports of studies were identified.

DATA EXTRACTION

Descriptions of the principal results and calculation of number needed to treat (NNT) and number needed to harm (NNH) for relevant dichotomous outcomes were extracted from the available study reports and other sources of information.

DATA SYNTHESIS

LDX is a central nervous system stimulant indicated for the treatment of moderate to severe BED. The recommended dose range is 50-70 mg/day. Approval for the treatment of BED was based on a clinical development programme that included an 11-week Phase II proof-of-concept, placebo-controlled study, testing fixed doses of LDX 30, 50 and 70 mg/day, and two 12-week Phase III placebo-controlled studies examining LDX 50-70 mg/day. Statistically significant reductions in binge eating days/week, the primary outcome measure, were observed for LDX doses of 50 and 70 mg/day, with effect sizes in the Phase III trials ranging from 0.83 to 0.97. The pooled NNT for response across all trials (as defined by a Clinical Global Impressions-Improvement score of 'very much improved' or 'much improved') for LDX vs. placebo was 3 (95% CI 3-4), and NNT for remission (as defined by 4-week cessation of binge eating) for LDX vs. placebo was 4 (95% CI 4-6). Reductions in weight ranged between 5.2% and 6.25% for LDX 50 or 70 mg/day. Discontinuation rates because of adverse events (AEs) were low; NNH for discontinuation because of an AE for LDX vs. placebo was 44 (95% CI 23-1971). The most commonly encountered AEs (incidence ≥ 10% and greater than the rate for placebo) were dry mouth, decreased appetite, insomnia and headache, with NNH values vs. placebo of 4 (95% CI 3-5), 11 (95% CI 8-17), 11 (95% CI 8-18) and 19 (95% CI 11-75), respectively.

CONCLUSIONS

LDX is the first pharmacological agent that has received regulatory approval for the treatment of BED. LDX 50 or 70 mg/day significantly reduced BED symptoms as measured by the number of binge eating days per week. Effect sizes were highly robust. Pending clinical trials include a long-term study examining maintenance of efficacy.

The use of lisdexamfetamine dimesylate for the treatment of ADHD and other psychiatric disorders

Lisdexamfetamine dimesylate (LDX) is a long-acting oral prodrug stimulant. It is inactive until enzymatically hydrolyzed in the blood to active D-amphetamine. The pharmacological action of this compound involves blocking norepinephrine (NE) and dopamine reuptake into presynaptic neurons and promoting the release of NE and dopamine into the extraneuronal space. LDX has been approved for treating ADHD, which is the most common psychiatric disorder in children and adolescents. Also, LDX has been proposed for other psychiatric conditions related with dopaminergic and NE CNS. LDX is the first long-acting oral prodrug indicated for the treatment of ADHD in children (6-12 years), adolescents (13-17 years) and in adults in the USA and Canada, whereas, in Europe, LDX is licensed in several countries for the treatment of children and adolescents with ADHD who have had a clinically inadequate response to methylphenidate. This article covers the most important pharmacological aspects of LDX as well as data on the efficacy, tolerability and safety of this long-acting amphetamine prodrug collected from clinical studies recently published in the literature.

Isotope-dilution mass spectrometric quantification of the prodrug lisdexamfetamine in human urine in doping control analysis

RATIONALE

Therapeutic approaches concerning attention-deficit hyperactivity disorder (ADHD) commonly include the administration of drugs amplifying cerebral dopamine and norepinephrine signals. Among these, compounds belonging to the Prohibited List as established by the World Anti-Doping Agency (WADA) are present such as amfetamine or methylphenidate, and abuse of these can result in sanctions for athletes. The recently approved therapeutic lisdexamfetamine represents a slow-release prodrug of amfetamine for ADHD treatment. In order to support doping control laboratories in differentiating the abuse of amfetamine from a therapeutic administration of lisdexamfetamine, the determination of the prodrug from urine is desirable. Since approximately 2% of lisdexamfetamine are eliminated intact into urine, a liquid chromatography/high-resolution/high accuracy mass spectrometric method was developed, allowing the target analyte and one of its metabolites (4-hydroxyamfetamine sulfate) to be accurately quantified.

METHODS

Urine samples were fortified with fourfold deuterated lisdexamfetamine and analyzed directly using ultrahigh-performance liquid chromatography (UHPLC) interfaced via electrospray ionization to a second-generation quadrupole-orbitrap mass spectrometer. The assay was characterized concerning specificity, limits of quantification (0.15-5 ng/mL), intraday and interday imprecision (4-22%), accuracy (90-120%), linearity, and ion suppression/enhancement effects. A patient's urine samples were analyzed to provide proof-of-principle data demonstrating that the intact prodrug lisdexamfetamine is detectable in urine up to 11 h post-administration at concentrations up to 80 ng/mL. Moreover, amfetamine and sulfoconjugated 4-hydroxyamfetamine were measured, yielding up to 1146 and 56 ng/mL, respectively.

CONCLUSIONS

Considering the observed comparably low urinary concentrations of lisdexamfetamine and 4-hydroxyamfetamine sulfate, the preferred minimally labor-intense sample preparation, and the necessity of fast and robust result generation, the employed instrumental setup proved fit-for-purpose in sports drug testing.

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.

Overdose of drugs for attention-deficit hyperactivity disorder: clinical presentation, mechanisms of toxicity, and management

The prevalence of attention-deficit hyperactivity disorder (ADHD) in the USA is estimated at approximately 4-9% in children and 4% in adults. It is estimated that prescriptions for ADHD medications are written for more than 2.7 million children per year. In 2010, US poison centers reported 17,000 human exposures to ADHD medications, with 80% occurring in children <19 years old and 20% in adults. The drugs used for the treatment of ADHD are diverse but can be roughly separated into two groups: the stimulants such as amphetamine, methylphenidate, and modafinil; and the non-stimulants such as atomoxetine, guanfacine, and clonidine. This review focuses on mechanisms of toxicity after overdose with ADHD medications, clinical effects from overdose, and management. Amphetamine, dextroamphetamine, and methylphenidate act as substrates for the cellular monoamine transporter, especially the dopamine transporter (DAT) and less so the norepinephrine (NET) and serotonin transporter. The mechanism of toxicity is primarily related to excessive extracellular dopamine, norepinephrine, and serotonin. The primary clinical syndrome involves prominent neurological and cardiovascular effects, but secondary complications can involve renal, muscle, pulmonary, and gastrointestinal (GI) effects. In overdose, the patient may present with mydriasis, tremor, agitation, hyperreflexia, combative behavior, confusion, hallucinations, delirium, anxiety, paranoia, movement disorders, and seizures. The management of amphetamine, dextroamphetamine, and methylphenidate overdose is largely supportive, with a focus on interruption of the sympathomimetic syndrome with judicious use of benzodiazepines. In cases where agitation, delirium, and movement disorders are unresponsive to benzodiazepines, second-line therapies include antipsychotics such as ziprasidone or haloperidol, central alpha-adrenoreceptor agonists such as dexmedetomidine, or propofol. Modafinil is not US FDA approved for treatment of ADHD; however, it has been shown to improve ADHD signs and symptoms and has been used as an off-label pharmaceutical for this diagnosis in both adults and children. The mechanism of action of modafinil is complex and not fully understood. It is known to cause an increase in extracellular concentrations of dopamine, norepinephrine, and serotonin in the neocortex. Overdose with modafinil is generally of moderate severity, with reported ingestions of doses up to 8 g. The most common neurological effects include increased anxiety, agitation, headache, dizziness, insomnia, tremors, and dystonia. The management of modafinil overdose is largely supportive, with a focus on sedation, and control of dyskinesias and blood pressure. Atomoxetine is a selective presynaptic norepinephrine transporter inhibitor. The clinical presentation after overdose with atomoxetine has generally been mild. The primary effects have been drowsiness, agitation, hyperactivity, GI upset, tremor, hyperreflexia, tachycardia hypertension, and seizure. The management of atomoxetine overdose is largely supportive, with a focus on sedation, and control of dyskinesias and seizures. Clonidine is a synthetic imidazole derivative with both central and peripheral alpha-adrenergic agonist actions. The primary clinical syndrome involves prominent neurological and cardiovascular effects, with the most commonly reported features of depressed sensorium, bradycardia, and hypotension. While clonidine is an anti-hypertensive medication, a paradoxical hypertension may occur early with overdose. The clinical syndrome after overdose of guanfacine may be mixed depending on central or peripheral alpha-adrenoreceptor effects. Initial clinical effects may be drowsiness, lethargy, dry mouth, and diaphoresis. Cardiovascular effects may depend on time post-ingestion and may present as hypotension or hypertension. The management of guanfacine overdose is largely supportive, with a focus on support of blood pressure. Overdose with ADHD medications can produce major morbidity, with many cases requiring intensive care medicine and prolonged hospital stays. However, fatalities are rare with appropriate care.

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.

Metabolism of the prodrug lisdexamfetamine dimesylate in human red blood cells from normal and sickle cell disease donors

OBJECTIVES

Lisdexamfetamine dimesylate (LDX), a long-acting pro-drug psychostimulant, requires conversion to d-amphetamine for therapeutic activity. Conversion of LDX to d-amphetamine occurs primarily in the blood, specifically red blood cells (RBCs). These in vitro studies examine potential conversion in blood-containing pathologically deformed RBCs.

METHODS

Fresh blood samples from two human male donors with sickle cell disease and two healthy control donors were incubated for up to 4 h with LDX (1 µg/mL) at 37°C. LDX and d-amphetamine were measured by a validated liquid chromatographic mass spectrometric (LC/MS/MS) method.

RESULTS

In incubations of blood from the two donors with sickle cell disease, LDX concentrations declined over time such that 14.1% and 15.3% of initial LDX remained after 4 h. Similarly, in incubations of blood from two healthy donors, LDX concentrations declined over time with 13.1% and 10.5% of initial LDX remaining. Half-life of LDX was 1.30 and 1.36 h for the donors with sickle cell disease and 1.15 and 1.13 h for the healthy donors. Concurrent with the decrease in LDX concentrations, the d-amphetamine concentrations rose in a similar fashion in samples from healthy controls and sickle cell donors. d-Amphetamine levels detected at 4 h with LC/MS/MS were 297.0 ng/mL and 324.3 ng/mL in the two healthy donors and 304.5 ng/mL and 286.6 ng/mL in the two sickle cell donors.

CONCLUSIONS

While the current findings are derived from in vitro investigations on a small number of samples and the applicability of this in vitro experimental system to in vivo function has not been established, biotransformation of LDX and the resulting delivery of active d-amphetamine from LDX are likely to be similar in individuals with or without sickle cell disease.

Double-blind, placebo-controlled, two-period, crossover trial to examine the pharmacokinetics of lisdexamfetamine dimesylate in healthy older adults

BACKGROUND

Pharmacokinetic and safety data on stimulants in older adults are limited. The objective of this study was to characterize the pharmacokinetics of lisdexamfetamine dimesylate (LDX), a d-amphetamine prodrug, in older adults.

METHODS

In this two-period crossover trial, healthy adults (n = 47) stratified by age (55-64, 65-74, and ≥ 75 years) and gender received randomized, double-blind, single doses of LDX 50 mg or placebo. Baseline creatinine clearance, d-amphetamine and intact LDX pharmacokinetics, and safety were assessed.

RESULTS

Mean (±standard deviation) baseline creatinine clearance in participants aged 55-64, 65-74, and ≥ 75 years was 102.5 ± 26.1, 105.3 ± 23.1, and 94.9 ± 27.3 mL per minute, respectively. In the groups aged 55-64, 65-74, and ≥ 75 years, the mean maximum plasma d-amphetamine concentration in men was 44.2 ± 11.1, 47.7 ± 7.0, and 53.4 ± 19.4 ng/mL, respectively; area under the concentration time curve from time 0 extrapolated to infinity (AUC(0-inf)) was 915.0 ± 164.9, 1123.0 ± 227.0, and 1325.0 ± 464.4 nghour/mL; median time to reach peak plasma concentration was 4.5, 3.5, and 5.5 hours; in women, mean maximum plasma d-amphetamine concentration was 51.0 ± 6.7, 50.2 ± 6.8, and 64.3 ± 12.1 ng/mL, AUC(0-inf) was 1034.5 ± 154.6, 988.4 ± 80.5, and 1347.8 ± 198.9 ng hour/mL, and median time to reach peak plasma concentration was 3.5, 4.1, and 5.5 hours, respectively. d-Amphetamine clearance was unrelated to baseline creatinine clearance. Five participants aged 55-64 years reported treatment-emergent adverse events (versus one each aged 65-74 and ≥ 75 years), and as did six women (versus one man). No trends in blood pressure or pulse changes were seen with LDX according to age. In participants aged 55-64, 65-74, and ≥ 75 years, the mean change from time-matched baseline pulse ranged from -5.0 to 14.7, -4.3 to 9.5, and -3.0 to 14.7 beats per minute; for systolic blood pressure, from -3.9 to 18.5 mmHg, -2.1 to 14.5 mmHg, and -5.9 to 16.0 mmHg; for diastolic blood pressure from -2.5 to 8.3 mmHg, from -0.8 to 9.4 mmHg, and -0.6 to 9.5 mmHg. Vital sign changes were similar between men and women.

CONCLUSION

Clearance of d-amphetamine decreased with age and was unrelated to creatinine clearance. No trends in pulse or blood pressure changes with LDX were seen according to age. The safety profile of LDX was consistent with prior observations in younger adult study participants.

Update on optimal use of lisdexamfetamine in the treatment of ADHD

Lisdexamfetamine (LDX) has been a recent addition to the treatment armamentarium for Attention Deficit Hyperactivity Disorder (ADHD). It is unique among stimulants as it is a prodrug, and has been found to be safe and well-tolerated medication in children older than 6 years, adolescents and adults. It has a smooth onset of action, exerts its action up to 13 hours and may have less rebound symptoms. LDX has proven to be effective in the treatment of ADHD in placebo controlled trials, and improved performance in simulated academic and work environments have been noticed. Both stimulant-naïve and stimulant-exposed patients with ADHD appear to benefit from LDX. It has also shown some promise in improving emotional expression and executive function of patients with ADHD. Adverse effects such as decrease in sleep, loss of appetite and others have been reported with LDX use, just as with other stimulant formulations. Since most such studies exclude subjects with preexisting cardiac morbidity, prescribing precautions should be taken with LDX in such subjects, as with any other stimulant. Study subjects on LDX have been reported to have low scores on drug likability scales, even with intravenous use; as a result, LDX may have somewhat less potential for abuse and diversion. There is a need for future studies comparing other long acting stimulants with LDX in ADHD; in fact clinical trials comparing LDX with OROS (osmotic controlled-release oral delivery system) methylphenidate are currently underway. Furthermore, the utility of this medication in other psychiatric disorders and beyond ADHD is being investigated.

Efficacy of lisdexamfetamine dimesylate in adults with attention-deficit/hyperactivity disorder previously treated with amphetamines: analyses from a randomized, double-blind, multicenter, placebo-controlled titration study

Background

To examine the efficacy of lisdexamfetamine dimesylate (LDX) in adults with attention-deficit/hyperactivity disorder (ADHD) who remained symptomatic (ADHD Rating Scale IV [ADHD-RS-IV] total score >18) on amphetamine (AMPH) therapy (mixed AMPH salts and/or d-AMPH formulations) prior to enrollment in a 4-week placebo-controlled LDX trial vs the overall study population. In these post hoc analyses from a multicenter, randomized, double-blind, forced-dose titration study, clinical efficacy of LDX (30-70 mg/d) in adults with ADHD receiving AMPH treatment at screening vs the overall study population was evaluated. ADHD symptoms were assessed using the ADHD-RS-IV with adult prompts at screening, baseline (after prior treatment washout), and endpoint. Safety assessments included treatment-emergent adverse events (TEAEs), vital signs, laboratory findings, and electrocardiogram.

Results

Of 414 participants (62, placebo; 352, LDX) included in the overall study population, 41 were receiving AMPH therapy at screening (2, placebo; 39, LDX); mean AMPH dose was 35.0 and 34.1 mg/d for participants in placebo and all LDX groups, respectively. Of the 41 participants, 36 remained symptomatic (ADHD-RS-IV >18) at screening despite receiving AMPH. For the 36 participants in the placebo (n = 2) and LDX (n = 34) groups, respectively, at endpoint, mean change from screening ADHD-RS-IV total scores were -5.5 and -14.8 and from baseline scores were -13.5 and -17.8. For the overall study population, endpoint mean change from baseline ADHD-RS-IV total scores were -7.8 for placebo and -17.5 for LDX. In the prior AMPH subgroup, 2/2 (100.0%) in the placebo group and 22/39 (56.4%) participants in the LDX (all doses) group reported any TEAE. Events that occurred in ≥5% for LDX were dry mouth (5/39; 12.8%), headache (5/39; 12.8%), fatigue (3/39; 7.7%), insomnia (3/39; 7.7%), decreased appetite (2/39; 5.1%), and nausea (2/39; 5.1%). None of these events occurred in the 2 placebo patients with prior AMPH use.

Conclusion

In these post hoc analyses, adults with significant baseline ADHD symptoms despite adequate AMPH treatment dose showed similar improvements in ADHD symptoms with LDX treatment as the overall study population. Prospective studies are needed to confirm these findings. The safety profile of LDX in the overall study population was consistent with long-acting psychostimulant use.

Trial registry

Study to Assess the Safety and Efficacy of NRP104 in Adults With Attention-Deficit Hyperactivity Disorder (ADHD). Clinicaltrials.gov Identifier: NCT00334880

An update on lisdexamfetamine dimesylate for the treatment of attention deficit hyperactivity disorder

INTRODUCTION

The efficacy and safety of stimulants for the pharmacologic management of attention deficit hyperactivity disorder (ADHD) is well documented. The US Food and Drug Administration approval of additional classes of medication even within stimulant treatments expands the prescribing options for practitioners. The focus of this paper is the prodrug amphetamine stimulant, lisdexamfetamine (LDX) , which is an example of such an agent with a novel delivery system.

AREAS COVERED

This review covers the proof-of-concept and later studies of LDX to describe its use to treat ADHD in pediatric and adult populations. A literature search and review of LDX were carried out using the PubMed database up to August 2012.

EXPERT OPINION

Clinical studies of LDX in children and adults with ADHD demonstrate its tolerability and its efficacy in reducing ADHD symptoms. Future research should be less restrictive in order to address some of the unmet needs in ADHD treatment. The inclusion of patients with ADHD and co-occurring mental health disorders and/or medical conditions is typically not studied in clinical trials nor is the prior ADHD treatment exposure of study participants. The preschool age population also is understudied in recently approved ADHD treatments such as LDX. Finally, how to approach the treatment of participants or first-degree relatives with a medical history or presence of substance use disorder presents an ongoing clinical challenge.

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.

[The medical treatment of attention deficit hyperactivity disorder (ADHD) with amphetamines in children and adolescents]

INTRODUCTION

Psychostimulants (methylphenidate and amphetamines) are the drugs of first choice in the pharmacological treatment of children and adolescents with attention deficit hyperactivity disorder (ADHD).

OBJECTIVE

We summarize the pharmacological characteristics of amphetamines and compare them with methylphenidate, special emphasis being given to a comparison of effects and side effects of the two substances. Finally, we analyze the abuse and addiction risks.

METHODS

Publications were chosen based on a Medline analysis for controlled studies and meta-analyses published between 1980 and 2011; keywords were amphetamine, amphetamine salts, lisdexamphetamine, controlled studies, and metaanalyses.

RESULTS AND DISCUSSION

Amphetamines generally exhibit some pharmacologic similarities with methylphenidate. However, besides inhibiting dopamine reuptake amphetamines also cause the release of monoamines. Moreover, plasma half-life is significantly prolonged. The clinical efficacy and tolerability of amphetamines is comparable to methylphenidate. Amphetamines can therefore be used if the individual response to methylphenidate or tolerability is insufficient before switching to a nonstimulant substance, thus improving the total response rate to psychostimulant treatment. Because of the high abuse potential of amphetamines, especially in adults, the prodrug lisdexamphetamine (Vyvanse) could become an effective treatment alternative. Available study data suggest a combination of high clinical effect size with a beneficial pharmacokinetic profile and a reduced abuse risk.

CONCLUSIONS

In addition to methylphenidate, amphetamines serve as important complements in the psychostimulant treatment of ADHD. Future studies should focus on a differential comparison of the two substances with regard to their effects on different core symptom constellations and the presence of various comorbidities.

Lisdexamfetamine dimesylate: a new therapeutic option for attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is associated with substantial functional, clinical and economic burdens. It is among the most common psychiatric disorders in children and adolescents, and often persists into adulthood. Both medication and psychosocial interventions are recommended for the treatment of ADHD. However, ADHD treatment practices vary considerably, depending on medication availability, reimbursement and the evolution of clinical practice in each country. In Europe, stimulants and atomoxetine are widely available medications for the treatment of ADHD, whereas in the US approved treatment options also include extended-release formulations of clonidine and guanfacine. Lisdexamfetamine dimesylate (lisdexamfetamine) is a long-acting, prodrug formulation of dexamfetamine. It is currently licensed in the US, Canada and Brazil, and is undergoing phase III studies in Europe. We performed a PubMed/MEDLINE search looking for recent (2005-2012) scientific papers regarding the pharmacokinetics, pharmacodynamics, efficacy and safety of lisdexamfetamine. The lisdexamfetamine molecule is therapeutically inactive and is enzymatically hydrolysed, primarily in the blood, to the active dexamfetamine. This conversion is unaffected by gastrointestinal pH and variations in normal transit times. Lisdexamfetamine was developed with the goal of providing an extended duration of effect that is consistent throughout the day. Clinical trials have demonstrated robust clinical efficacy of lisdexamfetamine in the treatment of children, adolescents and adults with ADHD with dose-dependent improvements in the core symptoms of ADHD. Studies have further shown that the duration of action of lisdexamfetamine continues for 13 hours post-dosing in children and for 14 hours in adults. The tolerability profile of lisdexamfetamine is consistent with those of other stimulant medications, with decreased appetite, insomnia, abdominal pain and irritability among the more frequent treatment-emergent adverse events, most of which are mild to moderate in intensity and transient in nature. There are currently no parallel-group, head-to-head trial data comparing the efficacy and safety of lisdexamfetamine with other medications for ADHD. However, the available data, including a large effect size and consistent plasma concentrations throughout the day, suggest that lisdexamfetamine is a useful treatment option for patients with ADHD.

The use of lisdexamfetamine dimesylate for the treatment of ADHD

ADHD is a common neurobehavioral disorder characterized by significant impairment in attention, hyperactivity and impulsivity. Symptoms begin in childhood and can persist into adulthood. Current data suggest that abnormal functioning of the prefrontal cortex, cortical and subcortical regions of the brain have roles in ADHD. All currently approved drugs used to treat ADHD enhance dopamine and norepinephrine signals in these regions. Lisdexamfetamine dimesylate (LDX) is a long-acting amphetamine prodrug indicated for the treatment of ADHD and has been shown to be effective in children, adolescents and adults. The prodrug properties of LDX make it a desirable treatment because of its long duration of effect, and low intrasubject and intersubject pharmacokinetic variability, and attenuated response on measures of abuse liability when compared with immediate-release amphetamine. However, LDX is still classified as a controlled substance. In this article, the pharmacokinetic parameters and efficacy and safety of LDX are reviewed.

Effect of lisdexamfetamine dimesylate on sleep in children with ADHD

OBJECTIVE

This study evaluated the potential effects of short-term treatment with lisdexamfetamine dimesylate (LDX) on both subjective and objective sleep characteristics in children aged 6 to 12 years (n = 24) with ADHD.

METHOD

Polysomnography (PSG) and actigraph measures as well as assessments of subjective sleep parameters were examined in children before and after treatment with either LDX or placebo in a randomized, double-blind, single-center, parallel-group study.

RESULTS

There was no statistically significant increase in the primary endpoint of latency to persistent sleep (LPS) for the LDX-treated group compared to the placebo group. Secondary PSG or actigraph results generally supported primary endpoint results. Subjective sleep measure results indicated the possibility that responses are influenced by sleep hygiene counseling before and throughout the study.

CONCLUSIONS

In this pilot sleep study in children with ADHD, LDX did not appear to contribute to any sleep disturbances as measured by both objective and subjective sleep parameters. The sample used in this study was small, and the multifarious nature of findings in this study warranted that the study conclusions be interpreted cautiously and that further study is required focusing on the influence of LDX on sleep in larger samples of ADHD children.

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

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

Absorption of lisdexamfetamine dimesylate and its enzymatic conversion to d-amphetamine

These studies investigated the absorption and metabolic conversion of lisdexamfetamine dimesylate (LDX), a prodrug stimulant that requires conversion to d-amphetamine for activity. Oral absorption of LDX was assessed in rat portal and jugular blood, and perfusion of LDX into isolated intestinal segments of anesthetized rats was used to assess regional absorption. Carrier-mediated transport of LDX was investigated in Caco-2 cells and Chinese hamster ovary (CHO) cells expressing human peptide transporter-1 (PEPT1). LDX metabolism was studied in rat and human tissue homogenates and human blood fractions. LDX was approximately10-fold higher in portal blood versus systemic blood. LDX and d-amphetamine were detected in blood following perfusion of the rat small intestine but not the colon. Transport of LDX in Caco-2 cells had permeability apparently similar to cephalexin and was reduced with concurrent PEPT1 inhibitor. Affinity for PEPT1 was also demonstrated in PEPT1-transfected CHO cells. LDX metabolism occurred primarily in whole blood (rat and human), only with red blood cells. Slow hydrolysis in liver and kidney homogenates was probably due to residual blood. The carrier-mediated absorption of intact LDX, likely by the high-capacity PEPT1 transporter, and subsequent metabolism to d-amphetamine in a high-capacity system in blood (ie, red blood cells) may contribute to the consistent, reproducible pharmacokinetic profile of LDX.

New and extended-action treatments in the management of ADHD: a critical appraisal of lisdexamfetamine in adults and children

Treatment guidelines from the American Academy of Child and Adolescent Psychiatry and the American Academy of Pediatrics state that stimulant medications have the most evidence for safety and efficacy in the treatment of childhood attention deficit hyperactivity disorder (ADHD). Longer-acting stimulants are thus considered as first-line for management of ADHD symptoms. Over the years, concerns about the abuse potential of stimulants have led to the development of alternative formulations of these agents. One such recent development, lisdexamfetamine (LDX) was FDA approved for treating ADHD in children in early 2007 and in adults in early 2008. LDX is a prodrug, which when orally ingested, is converted to l- lysine and active d-amphetamine, which is responsible for its therapeutic activity. This unique formulation may lead to a possible reduction of the abuse potential, by bypassing the first-pass metabolism. In fact, a statistically significant difference for the 'liking' effects on the Drug Questionnaire Response has been reported with intravenous LDX compared to d-amphetamine. LDX appears to have an efficacy and tolerability profile comparable to other extended-release stimulant formulations used to treat ADHD, but reduced potential for abuse-related liking effects when compared to equivalent amounts of immediate-release d-amphetamine. The most common adverse events include decreased appetite, insomnia, upper abdominal pain, headache, irritability, weight loss, and nausea.

Lisdexamfetamine dimesylate: a prodrug stimulant for the treatment of ADHD in children and adults

Attention-deficit/hyperactivity disorder (ADHD) is a highly genetic neuropsychiatric disorder that can cause impairment at school, work, home, and in social relationships. Once considered a childhood disorder, as many as 65% of children with ADHD continue to exhibit symptoms into adulthood. While a mainstay of ADHD patient care, immediate-release stimulant use has been constrained by concerns about safety, tolerability, and issues related to nonmedical use and abuse. These concerns have prompted interest in developing modified versions or new delivery systems for stimulants. Prodrugs have been used in pharmaceutical development to optimize delivery of an active drug or to minimize toxicity. Prodrugs are pharmacologically inactive compounds that require in vivo conversion to release therapeutically active medications. Lisdexamfetamine dimesylate (LDX) is an inactive, water-soluble prodrug in which d-amphetamine is bonded to l-lysine, a naturally occurring amino acid. After oral ingestion, LDX is metabolized into l-lysine and active d-amphetamine. This review of LDX presents the efficacy, safety, and pharmacokinetic profile of this novel stimulant medication, and is intended to help clinicians understand its role in treating children and adults with ADHD.