Lisdexamfetamine: A pharmacokinetic review

Role of vesicular monoamine transporter-2 for treating attention deficit hyperactivity disorder: a review

RATIONALE

The Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) classifies attention deficit hyperactivity disorder (ADHD) as a neurodevelopmental disorder that interferes with human functioning and development. As the clinical presentation of ADHD involves a deficiency in executive function, neurocognitive deficits involving distinctive neuropathological changes must be present for clinical diagnosis.

OBJECTIVES

The vesicular monoamine transporter (VMAT), specifically VMAT-2, plays a role in ADHD pathogenesis. In addition, experimental data show that the stimulants (amphetamines and methylphenidate) are first-line treatments for the condition because of their extensive interaction with VMAT-2. The interactions of peptides, bupropion, and nutritional supplements with VMAT-2 receptors have been researched, but more evidence is needed to elucidate their pharmacodynamic properties. Therefore, this literature review evaluated the current pharmacological treatment modalities, peptides, and nutritional supplements for ADHD that target the VMAT-2 system.

METHODS, RESULTS, AND CONCLUSIONS

We obtained relevant studies from several platforms, including the National Center for Biotechnology, Clinical Key, Access Medicine, and PubMed. From the results of these studies, we observed that stimulants interact highly with the VMAT-2 transporter, with omega-3 fatty acids, peptides, and bupropion exerting some modulatory activity on VMAT-2. These agents should be considered for the future treatment of ADHD, although clinical-level research involving human participants is necessary.

Lisdexamfetamine dimesylate-exposition in male rats during the peripubertal period impairs inflammatory mechanisms, antioxidant activity, and apoptosis process in kidneys of male pubertal rats

Lisdexamfetamine dimesylate (LDX) is a prodrug of dextroamphetamine, which has been widely recommended for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD). There are still no data in the literature relating the possible toxic effects of LDX in the kidney. Therefore, the present study aims to evaluate the effects of LDX exposure on morphological, oxidative stress, cell death and inflammation parameters in the kidneys of male pubertal Wistar rats, since the kidneys are organs related to the excretion of most drugs. For this, twenty male Wistar rats were distributed randomly into two experimental groups: LDX group-received 11,3 mg/kg/day of LDX; and Control group-received tap water. Animals were treated by gavage from postnatal day (PND) 25 to 65. At PND 66, plasma was collected to the biochemical dosage, and the kidneys were collected for determinations of the inflammatory profile, oxidative status, cell death, and for histochemical, and morphometric analyses. Our results show that there was an increase in the number of cells marked for cell death, and a reduction of proximal and distal convoluted tubules mean diameter in the group that received LDX. In addition, our results also showed an increase in MPO and NAG activity, indicating an inflammatory response. The oxidative status showed that the antioxidant system is working undisrupted and avoiding oxidative stress. Therefore, LDX-exposition in male rats during the peripubertal period causes renal changes in pubertal age involving inflammatory mechanisms, antioxidant activity and apoptosis process.

Single Dose Comparative Bioavailability Study of Lisdexamfetamine Dimesylate as Oral Solution Versus Reference Hard Capsules in Healthy Volunteers

Lisdexamfetamine is an inactive prodrug of dexamfetamine that is used for the second-line treatment of attention-deficit/hyperactivity disorder (ADHD) and moderate to severe binge eating disorder (BED). Once in the blood, the prodrug is hydrolyzed in erythrocyte cytosol, thus releasing the active dexamfetamine. We here present a fully validated HPLC-MS/MS analytical method for simultaneous determination of lisdexamfetamine and dexamfetamine in human plasma and the first published comparative bioavailability study of lisdexamfetamine including a GMP finished product formulated as oral solution. The Test (T)/Reference (R) ratios for the geometric means (%) of the primary pharmacokinetic (PK) parameters and their corresponding two-sided 90% confidence intervals (CIs) were contained within the predefined regulatory limits of 80.00–125.00% for both lisdexamfetamine and dexamfetamine. While for the lisdexamfetamine prodrug, PK results for the two formulations were slightly different due to the distinct dissolution state at administration, the PK parameters calculated for dexamfetamine were almost identical. A potential explanation of this phenomenon, already described in literature, is that biotransformation of lisdexamfetamine by red blood cells (rather than its release within the gastrointestinal tract) is the process controlling the rate of dexamfetamine delivery.

Analysis of methylphenidate, ethylphenidate, lisdexamfetamine, and amphetamine in oral fluid by liquid chromatography-tandem mass spectrometry

Oral fluid is an alternative matrix that has proven to be useful for the detection of drugs. Oral fluid is easy to collect, noninvasive, and may indicate recent drug use. There are limited methods available that analyze cognitive stimulants in oral fluid. Cognitive stimulants are used to treat attention-deficit/hyperactivity disorder (ADHD), a neurological disorder that emerges from lack of dopamine in the brain. To combat this disorder, medications inhibit dopamine and norepinephrine reuptake by blocking transporters in the brain. Though commonly diagnosed in children, ADHD may extend beyond adolescence and abuse of medications in college students is not uncommon. The goal of this study was to develop and validate a quantitative method for methylphenidate, ethylphenidate, lisdexamfetamine, and amphetamine in oral fluid using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Analytes were isolated by solid-phase extraction and analyzed on an Agilent 1290 Infinity II Liquid Chromatograph coupled to an Agilent 6470 Triple Quadrupole Mass Spectrometer. The linear range was 0.5-100 ng/ml (except lisdexamfetamine at 5-500 ng/ml). Bias and between-run precision were acceptable (±11.0% bias and ±12.2%CV). No interferences or carryover were observed and dilution integrity was sustained. This validated method was applied to four authentic oral fluid samples collected with Quantisal^® devices from college students. Lisdexamfetamine was quantified in one sample at 5.8 ng/ml while amphetamine was quantified in all four samples at 6.0-78.8 ng/ml. This is the first known quantitative method in oral fluid that includes these analytes using LC-MS/MS and may give rise to interpretive value in a forensic toxicology setting.

Practitioner's review: medication for children and adolescents with autism spectrum disorder (ASD) and comorbid conditions

Alleviating the multiple problems of children with autism spectrum disorder (ASD) and its comorbid conditions presents major challenges for the affected children, parents, and therapists. Because of a complex psychopathology, structured therapy and parent training are not always sufficient, especially for those patients with intellectual disability (ID) and multiple comorbidities. Moreover, structured therapy is not available for a large number of patients, and pharmacological support is often needed, especially in those children with additional attention deficit/hyperactivity and oppositional defiant, conduct, and sleep disorders.

Oral Drug Delivery: Conventional to Long Acting New-Age Designs

The Oral route of administration forms the heartwood of the ever-growing tree of drug delivery technology. It is one of the most preferred dosage forms among patients and controlled release community. Despite the high patient compliance, the deliveries of anti-cancerous drugs, vaccines, proteins, etc. via the oral route are limited and have recorded a very low bioavailability. The oral administration must overcome the physiological barriers (low solubility, permeation and early degradation) to achieve efficient and sustained delivery. This review aims at highlighting the conventional and modern-age strategies that address some of these physiological barriers. The modern age designs include the 3D printed devices and formulations. The superiority of 3D dosage forms over conventional cargos is summarized with a focus on long-acting designs. The innovations in Pharmaceutical organizations (Lyndra, Assertio and Intec) that have taken giant steps towards commercialization of long-acting vehicles are discussed. The recent advancements made in the arena of oral peptide delivery are also highlighted. The review represents a comprehensive journey from Nano-formulations to micro-fabricated oral implants aiming at specific patient-centric designs.

Use of Lisdexamfetamine or Amphetamine? Interpretation of Chiral Amphetamine Analyses

Amphetamine is frequently detected in forensic toxicological cases. Differentiating between the two isomers of amphetamine (d-amphetamine and l-amphetamine) and determining their relative proportion is fundamental to correctly interpret the results of toxicological analyses. The aim of this study was to examine the profile of amphetamine as well as storage stability of the isomers in authentic samples from patients chronically treated with lisdexamfetamine (LDX), the most prescribed medical amphetamine product in Sweden. Blood and urine samples were collected from 18 patients. The samples were analyzed with an achiral (racemate) method for quantification of amphetamine and with a chiral method to determine the proportion of each isomer of amphetamine. The median daily dose of LDX was 40 mg (range, 20-70 mg). The median amphetamine concentration was 0.06 µg/g (range, 0.02-0.15 µg/g) in blood and 6 µg/mL (range, 1-22 µg/mL) in urine. Only d-amphetamine was found in the blood and urine samples from the included patients. Furthermore, no formation of l-amphetamine occurred during storage for three months at 4°C, nine months at -20°C and three freeze-thaw cycles. The results from this study may be helpful in the interpretation of whether the source of identified amphetamine in biological samples are from LDX drug intake or not.

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.

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.

Updates on Genome-Wide Association Findings in Eating Disorders and Future Application to Precision Medicine

Heterogeneity, frequent diagnostic fluctuation across presentations, and global concerns with the absence of effective treatments all encourage science that moves the field toward individualized or precision medicine in eating disorders. We review recent advances in psychiatric genetics focusing on genome-wide association studies (GWAS) in eating disorders. Given that the only eating disorder to be the subject of GWAS to date is anorexia nervosa, we review anorexia GWAS and enumerate the prospects and challenges of a genomics-driven approach towards personalized intervention in eating disorders.

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).

Can a Person with Attention Deficit Hyperactivity Disorder be an Athlete?

Attention-deficit–hyperactivity disorder (ADHD) is a common neuropsychiatric disorder that impairs academic, social and occupational functioning in children, adolescents and adults. It is characterized by excessive activity, restlessness, and nervousness. The disease occurs in general at children before the age of 7 and usually is not easy to be detected, due to various symptoms. When the diagnosis is established the physician can prescribe two types of drugs, stimulants: amphetamine, dexamphetamine, lisdexamphetamine, methylphenidate, and non-stimulants such as: guanfacine, atomoxetine, and clonidine. So what can be done for a person who has ADHD, and wants to be an elite athlete? Due to the rules established by the World Anti-Doping Agency the stimulant drugs are prohibited in competition and if traces of a prohibited substance are detected in the sample of blood of the athlete his access to competition can be blocked from 2-4 years, from that date of the incident. Fortunately for some athletes the disease was acute in childhood but as they grew up the symptoms were reminiscent and they could concentrate at the sporting task that was supposed to be achieved. What about those athletes that still have the symptoms? Well, they can be treated with the non-stimulant drugs, but their doctor must monthly verify if the list of prohibited drugs has been changed. In conclusion we can say that ADHD can be an impediment, but with the help of parents, teachers, and physicians the athlete can achieve very good performances.

Review of Lisdexamfetamine Dimesylate in Adults With Attention-Deficit/Hyperactivity Disorder

Lisdexamfetamine dimesylate (LDX) is the first prodrug stimulant used for the treatment of attention-deficit/hyperactivity disorder (ADHD) dosed once daily. Due to its long-acting properties, LDX remains pharmacologically inactive until an enzymatic process predominantly associated with red blood cells converts it to the active ingredient, d-amphetamine and the amino acid lysine. The efficacy of LDX over placebo has been demonstrated in several studies in adults with moderate to severe ADHD with significant improvements noted in ADHD rating scales, Clinical Global Improvement scores, and assessments of executive function, for all doses of LDX (30-70 mg daily). Lisdexamfetamine dimesylate has demonstrated efficacy at 14 hours post dose in adults and may be used as a long-acting stimulant for managing ADHD symptoms, which may extend late into the day. Lisdexamfetamine dimesylate has demonstrated a safety profile consistent with long-acting stimulants use. Relevant English language articles were identified through computerized searches of MEDLINE (PubMed and EMBASE) from 1995 to 2016 using the following search terms: lisdexamfetamine dimesylate, attention-deficit hyperactivity disorder, NRP104, and Vyvanse.

A Phase 3, Multicenter, Open-Label, 12-Month Extension Safety and Tolerability Trial of Lisdexamfetamine Dimesylate in Adults With Binge Eating Disorder

BACKGROUND

A 12-month, open-label extension study assessed the long-term safety and tolerability of lisdexamfetamine dimesylate (LDX) in adults with binge eating disorder (BED).

METHODS

Adults (aged 18-55 y) with BED who completed 1 of 3 antecedent studies were enrolled in a 52-week, open-label extension study (dose optimization, 4 weeks [initial titration dose, 30-mg LDX; target doses, 50- or 70-mg LDX]; dose maintenance, 48 weeks). Safety evaluations included the occurrence of treatment-emergent adverse events (TEAEs), vital sign and weight assessments, and Columbia-Suicide Severity Rating Scale responses.

RESULTS

Of the 604 enrolled participants, 599 (521 women and 78 men) comprised the safety analysis set, and 369 completed the study. Mean (SD) LDX exposure was 284.3 (118.84) days; cumulative LDX exposure duration was 12 months or longer in 344 participants (57.4%). A total of 506 participants (84.5%) reported TEAEs (TEAEs leading to treatment discontinuation, 54 [9.0%]; severe TEAEs, 42 [7.0%]; serious TEAEs, 17 [2.8%]). Treatment-emergent adverse events reported in greater than or equal to 10% of participants were dry mouth (27.2%), headache (13.2%), insomnia (12.4%), and upper respiratory tract infection (11.4%). Mean (SD) changes from antecedent study baseline in systolic and diastolic blood pressure, pulse, and weight at week 52/early termination (n = 597) were 2.19 (11.043) and 1.77 (7.848) mm Hg, 6.58 (10.572) beats per minute, and -7.04 (7.534) kg, respectively. On the Columbia-Suicide Severity Rating Scale, there were 2 positive responses for any active suicidal ideations; there were no positive responses for suicidal behavior or completed suicides.

CONCLUSIONS

In this 12-month, open-label, extension study, the long-term safety and tolerability of LDX in adults with BED were generally consistent with its established profile for attention-deficit/hyperactivity disorder.