An evaluation of the cytochrome p450 inhibition potential of lisdexamfetamine in human liver microsomes

The Pharmacokinetics and Pharmacogenomics of Psychostimulants

The psychostimulants-amphetamine and methylphenidate-have been in clinical use for well more than 60 years. In general, both stimulants are rapidly absorbed with relatively poor bioavailability and short half-lives. The pharmacokinetics of both stimulants are generally linear and dose proportional although substantial interindividual variability in pharmacokinetics is in evidence. Amphetamine (AMP) is highly metabolized by several oxidative enzymes forming multiple metabolites while methylphenidate (MPH) is primarily metabolized by hydrolysis to the inactive metabolite ritalinic acid. At present, pharmacogenomic testing as an aid to guide dosing and personalized treatment cannot be recommended for either agent. Few pharmacokinetically based drug-drug interactions (DDIs) have been documented for either stimulant.

Strong and Selective Inhibitory Effects of the Biflavonoid Selamariscina A against CYP2C8 and CYP2C9 Enzyme Activities in Human Liver Microsomes

Like flavonoids, biflavonoids, dimeric flavonoids, and polyphenolic plant secondary metabolites have antioxidant, antibacterial, antiviral, anti-inflammatory, and anti-cancer properties. However, there is limited data on their effects on cytochrome P450 (P450) and uridine 5'-diphosphoglucuronosyl transferase (UGT) enzyme activities. In this study we evaluate the inhibitory potential of five biflavonoids against nine P450 activities (P450s1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A) in human liver microsomes (HLMs) using cocktail incubation and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The most strongly inhibited P450 activity was CYP2C8-mediated amodiaquine N-dealkylation with IC50 ranges of 0.019~0.123 μM. In addition, the biflavonoids-selamariscina A, amentoflavone, robustaflavone, cupressuflavone, and taiwaniaflavone-noncompetitively inhibited CYP2C8 activity with respective K_i values of 0.018, 0.083, 0.084, 0.103, and 0.142 μM. As selamariscina A showed the strongest effects, we then evaluated it against six UGT isoforms, where it showed weaker inhibition (UGTs1A1, 1A3, 1A4, 1A6, 1A9, and 2B7, IC50 1.7 μM). Returning to the P450 activities, selamariscina A inhibited CYP2C9-mediated diclofenac hydroxylation and tolbutamide hydroxylation with respective K_i values of 0.032 and 0.065 μM in a competitive and noncompetitive manner. However, it only weakly inhibited CYP1A2, CYP2B6, and CYP3A with respective K_i values of 3.1, 7.9, and 4.5 μM. We conclude that selamariscina A has selective and strong inhibitory effects on the CYP2C8 and CYP2C9 isoforms. This information might be useful in predicting herb-drug interaction potential between biflavonoids and co-administered drugs mainly metabolized by CYP2C8 and CYP2C9. In addition, selamariscina A might be used as a strong CYP2C8 and CYP2C9 inhibitor in P450 reaction-phenotyping studies to identify drug-metabolizing enzymes responsible for the metabolism of new chemicals.

Posterior Reversible Encephalopathy Syndrome in Clinical Toxicology: A Systematic Review of Published Case Reports

Background: Posterior reversible encephalopathy syndrome (PRES) is a rare clinical and radiological entity characterized by a typical brain edema. Although several case reports have described PRES in a context of poisoning, to our knowledge, a comprehensive assessment has not been performed. The aim of this systematic review was to raise awareness on poisoning-specific PRES features and to encourage consistent and detailed reporting of substance abuse–and drug overdose–associated PRES.

Methods: Medline/PubMed, Web of Science, and PsycINFO were screened through May 31, 2019, to systematically identify case reports and case series describing PRES associated with poisoning (i.e., alcohol, drugs, illicit drugs, natural toxins, chemical substances) in accidental context, intentional overdose, and substance abuse. The methodological quality of eligible case reports/series was assessed. Patients and exposure characteristics were recorded; relevant toxicological, radiological, and clinical data were extracted.

Results: Forty-one case reports and one case series reporting 42 unique cases were included. The median time to PRES onset from the start of exposure was 3 days (IQR 2–10). Acute high blood pressure, visual disturbance, and seizure were reported in 70, 55, and 50% of patients, respectively. The initial clinical presentation was alertness disorders in 64% of patients. Nine patients (21%) required mechanical ventilation. One-third of patients had at least one risk factor for PRES such as chronic hypertension (17%) or acute/chronic kidney failure (24%). The main imaging pattern (67%) was the combination of classical parieto-occipital edema with another anatomical region (e.g., frontal, basal ganglia, posterior fossa involvement). Vasogenic edema was found in 86% of patients. Intracranial hemorrhage occurred in 14% of patients. Both brain infarction and reversible cerebral vasoconstriction syndrome were diagnosed in 5% of patients. Three patients (12%, 3/25) had non-reversible lesions on follow-up magnetic resonance imaging. The median time required to hospital discharge was 14 days (IQR 7–18). Mortality and neurological recurrence rate were null.

Conclusions: Comorbidities such as chronic hypertension and kidney failure were less frequent than in patients with other PRES etiologies. Imaging analysis did not highlight a specific pattern for poisoning-induced PRES. Although less described, PRES in the context of poisoning, which shares most of the clinical and radiological characteristics of other etiologies, is not to be ignored.

Ochratoxin A-Induced Hepatotoxicity through Phase I and Phase II Reactions Regulated by AhR in Liver Cells

Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of the genera Aspergillus and Penicillium. OTA exists in a variety of foods, including rice, oats, and coffee and is hepatotoxic, with a similar mode of action as aflatoxin B1. The precise mechanism of cytotoxicity is not yet known, but oxidative damage is suspected to contribute to its cytotoxic effects. In this study, human hepatocyte HepG2 cells were treated with various concentrations of OTA (5-500 nM) for 48 h. OTA triggered oxidative stress as demonstrated by glutathione depletion and increased reactive oxygen species, malondialdehyde level, and nitric oxide production. Apoptosis was observed with 500 nM OTA treatment. OTA increased both the mRNA and protein expression of phase I and II enzymes. The same results were observed in an in vivo study using ICR mice. Furthermore, the relationship between phase I and II enzymes was demonstrated by the knockdown of the aryl hydrocarbon receptor (AhR) and NF-E2-related factor 2 (Nrf2) with siRNA. Taken together, our results show that OTA induces oxidative stress through the phase I reaction regulated by AhR and induces apoptosis, and that the phase II reaction is activated by Nrf2 in the presence of oxidative stress.

Drug-drug interactions and clinical considerations with co-administration of antiretrovirals and psychotropic drugs

Psychotropic medications are frequently co-prescribed with antiretroviral therapy (ART), owing to a high prevalence of psychiatric illness within the population living with HIV, as well as a 7-fold increased risk of HIV infection among patients with psychiatric illness. While ART has been notoriously associated with a multitude of pharmacokinetic drug interactions involving the cytochrome P450 enzyme system, the magnitude and clinical impact of these interactions with psychotropics may range from negligible effects on plasma concentrations to life-threatening torsades de pointes or respiratory depression. This comprehensive review summarizes the currently available information regarding drug-drug interactions between antiretrovirals and pharmacologic agents utilized in the treatment of psychiatric disorders-antidepressants, stimulants, antipsychotics, anxiolytics, mood stabilizers, and treatments for opioid use disorder and alcohol use disorder-and provides recommendations for their management. Additionally, overlapping toxicities between antiretrovirals and the psychotropic classes are highlighted. Knowledge of the interaction and adverse effect potential of specific antiretrovirals and psychotropics will allow clinicians to make informed prescribing decisions to better promote the health and wellness of this high-risk population.

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.

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 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.

The pharmacokinetics of DPH after the administration of a single intravenous or intramuscular dose in healthy dogs

The objective of this study was to determine the pharmacokinetics of diphenhydramine (DPH) in healthy dogs following a single i.v. or i.m. dose. Dogs were randomly allocated in two treatment groups and received DPH at 1 mg/kg, i.v., or 2 mg/kg, i.m. Blood samples were collected serially over 24 h. Plasma concentrations of DPH were determined by high-performance liquid chromatography, and noncompartmental pharmacokinetic analysis was performed with the commercially available software. Cardio-respiratory parameters, rectal temperature and effects on behaviour, such as sedation or excitement, were recorded. Diphenhydramine Clarea , Vdarea and T1/2 were 20.7 ± 2.9 mL/kg/min, 7.6 ± 0.7 L/kg and 4.2 ± 0.5 h for the i.v. route, respectively, and Clarea /F, Vdarea /F and T1/2 20.8 ± 2.7 mL/kg/min, 12.3 ± 1.2 L/kg and 6.8 ± 0.7 h for the i.m. route, respectively. Bioavailability was 88% after i.m. administration. No significant differences were found in physiological parameters between groups or within dogs of the same group, and values remained within normal limits. No adverse effects or changes in mental status were observed after the administration of DPH. Both routes of administration resulted in DPH plasma concentrations which exceeded levels considered therapeutic in humans.

Pharmacokinetics of coadministered guanfacine extended release and lisdexamfetamine dimesylate

BACKGROUND

In clinical practice, α₂-adrenoceptor agonists have been adjunctively administered with psychostimulants for the treatment of attention-deficit/hyperactivity disorder (ADHD). Two studies have examined the adjunctive use of guanfacine extended release (GXR, Intuniv®; Shire Development LLC, Wayne, PA, USA) with psychostimulants in children and adolescents with a suboptimal response to psychostimulant treatment. However, the potential for pharmacokinetic drug-drug interactions (DDIs) between GXR and lisdexamfetamine dimesylate (LDX, Vyvanse®; Shire US LLC, Wayne, PA, USA) has not been thoroughly evaluated.

OBJECTIVE

The primary objective of this study was to examine the pharmacokinetics of GXR 4 mg and LDX 50 mg given as single doses alone and in combination.

STUDY DESIGN

This was an open-label, randomized, three-period crossover, DDI study.

SETTING

The study was conducted in a single clinical research center.

PARTICIPANTS

Forty-two healthy adults were randomized in this study.

INTERVENTIONS

Subjects were administered single oral doses of GXR 4 mg, LDX 50 mg, or GXR and LDX in combination.

MAIN OUTCOME MEASURES

Blood samples collected predose and up to 72 h postdose assessed guanfacine, LDX, and d-amphetamine levels. Bioequivalence was defined as the 90% confidence intervals (CIs) of the geometric mean ratios of the area under the plasma concentration-time curve extrapolated to infinity (AUC0-∞) and maximum plasma concentration (Cmax) falling within the bioequivalence reference interval (0.80-1.25). Safety measures included adverse events, vital signs, and electrocardiograms (ECGs).

RESULTS

Forty subjects completed the study. Following administration of LDX alone or in combination with GXR, the statistical comparisons of the AUC0-∞ and Cmax of d-amphetamine fell entirely within the reference interval. For guanfacine, the 90% CI of the geometric mean ratio of AUC∞ for the two treatments was within the bioequivalence criteria, but for Cmax the upper bound of the 90% CI exceeded the standard range for bioequivalence by 7%. This relatively small change is unlikely to be clinically meaningful. Treatment-emergent adverse events (TEAEs) were reported by 42.9% of subjects; the most commonly reported TEAEs included dizziness (5.0, 7.3, and 7.3%) and headache (7.5, 4.9, and 7.3%) following administration of GXR, LDX, and GXR and LDX in combination, respectively. Clinically significant ECG abnormalities occurred in one subject following administration of LDX and in one subject following coadministration of GXR and LDX.

CONCLUSIONS

In healthy adults, coadministration of GXR and LDX did not result in a clinically meaningful pharmacokinetic DDI compared with either treatment alone. No unique TEAEs were observed with coadministration of GXR and LDX compared with either treatment alone.

Preclinical pharmacokinetics, pharmacology and toxicology of lisdexamfetamine: a novel d-amphetamine pro-drug

Lisdexamfetamine dimesylate (LDX) is a novel pro-drug of d-amphetamine that is currently used for the treatment of attention-deficit/hyperactivity disorder in children aged ≥ 6 years and adults. LDX is enzymatically cleaved to form d-amphetamine following contact with red blood cells, which reduces the rate of appearance and magnitude of d-amphetamine concentration in the blood and hence the brain when compared with immediate-release d-amphetamine at equimolar doses. Thus, the increase of striatal dopamine efflux and subsequent increase of locomotor activity following d-amphetamine is less prominent and slower to attain maximal effect following an equimolar dose of LDX. Furthermore, unlike d-amphetamine, the pharmacodynamic effects of LDX are independent of the route of administration underlining the requirement to be hydrolyzed by contact with red blood cells. It is conceivable that these pharmacokinetic and pharmacodynamic differences may impact the psychostimulant properties of LDX in the clinic. This article reviews the preclinical pharmacokinetics, pharmacology, and toxicology of LDX. This article is part of the Special Issue entitled 'CNS Stimulants'.

Lisdexamfetamine prodrug activation by peptidase-mediated hydrolysis in the cytosol of red blood cells

Lisdexamfetamine dimesylate (LDX) is approved as a once-daily treatment for attention-deficit/hyperactivity disorder in children, adolescents, and adults in some countries. LDX is a prodrug comprising d-amphetamine covalently linked to l-lysine via a peptide bond. Following oral administration, LDX is rapidly taken up from the small intestine by active carrier-mediated transport, probably via peptide transporter 1. Enzymatic hydrolysis of the peptide bond to release d-amphetamine has previously been shown to occur in human red blood cells but not in several other tissues. Here, we report that LDX hydrolytic activity resides in human red blood cell lysate and cytosolic extract but not in the membrane fraction. Among several inhibitors tested, a protease inhibitor cocktail, bestatin, and ethylenediaminetetra-acetic acid each potently inhibited d-amphetamine production from LDX in cytosolic extract. These results suggest that an aminopeptidase is responsible for hydrolytic cleavage of the LDX peptide bond, although purified recombinant aminopeptidase B was not able to release d-amphetamine from LDX in vitro. The demonstration that aminopeptidase-like activity in red blood cell cytosol is responsible for the hydrolysis of LDX extends our understanding of the smooth and consistent systemic delivery of d-amphetamine by LDX and the long daily duration of efficacy of the drug in relieving the symptoms of attention-deficit/hyperactivity disorder.

An open-label investigation of the pharmacokinetic profiles of lisdexamfetamine dimesylate and venlafaxine extended-release, administered alone and in combination, in healthy adults

Background

Lisdexamfetamine dimesylate (LDX), a prodrug consisting of d-amphetamine and l-lysine, is being studied in clinical trials of major depressive disorder. Additional drug-drug interaction studies were warranted.

Objective

This study aimed to describe the pharmacokinetics and safety of LDX and venlafaxine extended-release (VXR), alone or combined.

Study Design

The study was an open-label, two-arm, single-sequence crossover investigation with randomization to treatment sequence.

Setting and Participants

The study was conducted at two clinical study centres and included healthy adult males and females (18–45 years of age).

Intervention

The study included two single-sequence crossover designs: LDX alone followed by LDX + VXR (Treatment Arm A); and VXR alone followed by VXR + LDX (Treatment Arm B). Drug treatment was initiated on day 1 with once-daily LDX or VXR alone with 15 days’ titration to final dose (LDX 30, 50 and 70 mg for 5 days each; VXR 75, 150 and 225 mg for 5 days each). On days 16–30, VXR, titrated to a final dose of 225 mg, or LDX, titrated to a final dose of 70 mg, was coadministered for participants in Treatment Arm A or B, respectively. On days 31–38, VXR doses were tapered.

Main Outcome Measures

On days 1–2, 15–16 and 30–31, safety evaluations and blood samples were obtained pre-dose through 24 h post-dose for analysis of LDX, d-amphetamine, venlafaxine (VEN), and O-desmethylvenlafaxine (ODV). Combination treatment was considered bioequivalent to single treatment if 90 % confidence intervals (CIs) for geometric mean ratios (GMRs) of analytes fell within the interval 0.80–1.25 based on maximum plasma concentration (C_max) and area under the plasma concentration-time curve (AUC) from time zero to time of last measurable concentration (AUC_τ). Safety assessments included treatment-emergent adverse events (TEAEs), pulse rate and blood pressure (BP), clinical laboratory assessments, and 12-lead electrocardiograms (ECG).

Results

Among 80 enrolled subjects, 77 were included in pharmacokinetic and safety analyses. Combination LDX + VXR was bioequivalent to LDX alone, based on exposure to d-amphetamine (GMR [95 % CI], C_max (ng/mL): 0.97 [0.82, 1.14], AUC_τ: 0.95 [0.81, 1.12]). Exposure to VEN with LDX + VXR (vs. VXR alone) was increased (C_max: 1.10 [0.88, 1.38], AUC_τ: 1.13 [0.88, 1.45]) and ODV decreased (C_max: 0.91 [0.77, 1.06], AUC_τ: 0.83 [0.71, 0.96]), whereas composite VEN + ODV was bioequivalent to VXR alone (C_max: 0.96 [0.84, 1.09], AUC_τ: 0.98 [0.85, 1.13]). TEAEs with LDX or LDX + VXR were similar. Maximum mean increases from baseline were: pulse rate, +8.73 to 12.76 beats/min with either treatment alone and +17.67 to 20.85 beats/min with LDX + VXR; systolic BP, +4.32 to 6.56 mmHg with either treatment alone and +12.96 to 13.78 mmHg with LDX + VXR; diastolic BP, +5.39 to 5.74 mmHg with either treatment alone and +12.09 to 12.46 mmHg with LDX + VXR. One participant was withdrawn due to a serious TEAE (presyncope). No unexpected, clinically meaningful trends or changes from baseline in mean laboratory or ECG parameters were observed during the trial.

Conclusion

In healthy adults, combination LDX + VXR (vs. LDX alone) did not alter exposure to d-amphetamine. Although small changes in exposure to VEN (increased) and ODV (decreased) were seen with combination treatment, total VEN + ODV exposure showed no change (vs. VEN alone). LDX + VXR led to increases in BP and pulse rate, supporting existing recommendations for vital sign monitoring when using these medications.

The effect of lisdexamfetamine dimesylate on body weight, metabolic parameters, and attention deficit hyperactivity disorder symptomatology in adults with bipolar I/II disorder

OBJECTIVES

We primarily sought to determine the effect of adjunctive lisdexamfetamine dimesylate (LDX) on anthropometric and metabolic parameters. Our secondary aim was to evaluate the effect of LDX on attention deficit hyperactivity disorder (ADHD) symptom severity in adults with bipolar I/II disorder.

METHODS

Forty-five stable adults (i.e., non-rapid cycling, absence of clinically significant hypo/manic symptoms) with bipolar I/II disorder and comorbid ADHD were enrolled in a phase IV, 4-week, flexible dose, open-label study of adjunctive LDX. All subjects were initiated at 30 mg/day of adjunctive LDX for the first week with flexible dosing (i.e., 30-70 mg/day) between weeks 2 and 4.

RESULTS

Of the 45 subjects enrolled, 40 received adjunctive LDX (mean dose = 60 ± 10 mg/day). A statistically significant decrease from baseline to endpoint was evident in weight (p < 0.001), body mass index (p < 0.001), fasting total cholesterol (p = 0.011), low density lipoprotein cholesterol (p = 0.044), high density lipoprotein cholesterol (p = 0.015) but not triglycerides, or blood glucose. Significant reductions were also observed in leptin (p = 0.047), but not in ghrelin, adiponectin, or resistin levels. Diastolic blood pressure and pulse increased significantly over time but on average remained within the normal range (p < 0.001). There was a significant reduction from baseline to endpoint in the total score of the ADHD Self-Report Scale. Significant improvement from baseline to endpoint was also observed in the Montgomery-Åsberg Depression Rating Scale total score as well as the Clinical Global Impression Severity and Improvement score.

CONCLUSIONS

Short-term adjunctive LDX treatment was well tolerated by this sample of adults with stable bipolar I/II disorder. Lisdexamfetamine dimesylate offered beneficial effects on body weight, body mass index and several metabolic parameters. In addition to demonstrating short-term (i.e., 4 weeks) safety and tolerability, beneficial effects of LDX were also observed in mitigating depressive and ADHD symptom severity.

Clinical implications and management of drug-drug interactions between antiretroviral agents and psychotropic medications

Medications used in the treatment of human immunodeficiency virus (HIV) often have drug-drug interactions which complicate treatment of psychiatric illnesses in HIV-infected patients. Protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) are the two classes of HIV medications most likely to be involved with interactions, with the majority occurring via the cytochrome P450 (CYP450) system. These interactions can result in either increased or decreased exposure to psychotropic and antiretroviral medications, often requiring dosage adjustments and increased monitoring. This article reviews some of the major drug interactions with antiretroviral agents.

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.

[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.

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

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

Guanfacine extended release as adjunctive therapy to psychostimulants in children and adolescents with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder associated with a wide range of impairments. Psychostimulants are generally first-line pharmacotherapy, but symptom improvement is suboptimal in some patients. In these patients, clinicians frequently use a combination of psychostimulants and nonscheduled medications to manage ADHD, although published evidence supporting this practice was relatively scarce until recently.Guanfacine extended release (GXR), a selective alpha2A-adrenoceptor agonist, is approved as a monotherapy and adjunctive therapy to psychostimulant medications for ADHD in patients 6-17 years of age. Drug-drug interaction studies have demonstrated that the adjunctive administration of GXR with a long-acting methylphenidate preparation or lisdexamfetamine dimesylate did not change exposure to the active components of either medication in a clinically meaningful way compared with either treatment alone.Data supporting the potential efficacy of GXR adjunctive to psychostimulants were preliminarily observed in a 9-week, open-label, dose-escalation study and subsequent extension study (≤ 24 months) in subjects aged 6-17 years with suboptimal control of ADHD symptoms on psychostimulant monotherapy. In a subsequent 9-week, randomized, double-blind, placebocontrolled study of subjects aged 6-17 years with suboptimal response to a long-acting, extendedrelease, oral psychostimulant, adjunctive GXR (administered in the morning or evening) was associated with significantly greater symptom reduction than placebo and psychostimulant (ADHD Rating Scale IV [ADHD-RS-IV] total score, placebo-adjusted least squares mean reductions: GXR AM, -4.5, P = 0.002; GXR PM, -5.3, P < 0.001, based on Dunnett's test). Across multiple studies, the safety and tolerability profile of GXR administered adjunctively to psychostimulants has been consistent with the known profiles of each medication. Additional studies should further explore the role of adjunctive GXR in clinical practice to help identify those patients most likely to benefit from such therapy.

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.

Eosinophilic hepatitis in an adolescent during lisdexamfetamine dimesylate treatment for ADHD

We describe here the case of an adolescent who developed eosinophilic hepatitis during treatment for attention-deficit/hyperactivity disorder with lisdexamfetamine dimesylate (Vyvanse [Shire US Inc, Wayne, PA]). A 14-year-old boy presented to his primary care provider with abdominal pain and worsening jaundice. A diagnosis of hepatitis was made with biochemical markers, but evaluation failed to provide an etiology. Worsening hepatitis prompted hospitalization and initiation of steroids for presumed autoimmune hepatitis. A subsequent liver biopsy showed evidence of eosinophilic hepatitis. Known causes of eosinophilic hepatitis were ruled out, and a presumptive diagnosis of reaction to lisdexamfetamine dimesylate was made. Discontinuation of the medication led to resolution of the hepatitis and normalization of the liver biopsy. To our knowledge, this is the first report of hepatic injury attributed to lisdexamfetamine dimesylate.

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: in attention-deficit hyperactivity disorder in adults

Lisdexamfetamine dimesylate is a long-acting amfetamine prodrug that requires in vivo hydrolysis to gradually release active d-amfetamine. It is approved in the US for the treatment of attention-deficit hyperactivity disorder (ADHD) in adults and in children aged 6-12 years. In a study in adult stimulant abusers, oral lisdexamfetamine 50 or 100 mg showed less 'likability' response than immediate-release d-amfetamine 40 mg on the Drug Rating Questionnaire-Subject (DRQS) Liking scale. However, there was no significant difference between lisdexamfetamine 150 mg and d-amfetamine 40 mg. In a randomized, double-blind, phase III trial in adult patients with ADHD, oral lisdexamfetamine 30, 50 or 70 mg/day for 4 weeks caused a significantly greater improvement in ADHD-Rating Scale (ADHD-RS) total score than placebo; significant between-group differences favouring lisdexamfetamine were evident after 1 week. Lisdexamfetamine was generally well tolerated in adult patients with ADHD, with most treatment-emergent adverse events being of mild to moderate severity and consistent with the known effects of psychostimulants.

Lisdexamfetamine for treatment of attention-deficit/hyperactivity disorder

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, and safety of the prodrug lisdexamfetamine for the treatment of attention-deficit/hyperactivity disorder (ADHD) in children and adults and describe its potential place in therapy.

DATA SOURCES

Primary literature published between January 1, 1990, and August 1, 2008, was selected from PubMed using the search key words lisdexamfetamine, Vyvanse, and NRP104. References of selected publications were also reviewed. Posters and abstracts of research presented at national meetings were reviewed when available. The product labeling for Vyvanse was also used.

STUDY SELECTION AND DATA EXTRACTION

Preference was given to published, randomized, and controlled research describing the pharmacokinetics, efficacy, and safety of lisdexamfetamine. Noncontrolled studies, postmarketing reports, and poster presentations were considered secondly. All published studies were included.

DATA SYNTHESIS

Lisdexamfetamine is a prodrug of dextroamphetamine covalently bound to l-lysine, which is activated during first-pass metabolism. The unique pharmacokinetic profile owing to lisdexamfetamine's prodrug design and rate-limited enzymatic biotransformation allows for once-daily dosing with a duration of activity of approximately 12 hours. Lisdexamfetamine has been proven to reduce the symptoms of ADHD both in children aged 6-12 years and adults aged 18-55 years, decreasing ADHD rating scale scores by approximately 27 and 19 points, respectively. Adverse effects with an incidence greater than 10% during preclinical trials included appetite suppression, insomnia, and headache. Lisdexamfetamine's unique pharmacokinetic properties may provide additional safety with regard to reducing abuse potential. As with other central nervous system (CNS) stimulants, concerns regarding sudden cardiac death and adverse effects on growth also apply to lisdexamfetamine.

CONCLUSIONS

Lisdexamfetamine provides another amphetamine-based CNS stimulant option for treatment of children and adults with ADHD. However, its use may be limited by a lack of significant differentiation when compared with currently used stimulants and a lack of evidence to support its use in adolescents.

Lisdexamfetamine: a prodrug stimulant for ADHD

This article reviews the unique prodrug stimulant lisdexamfetamine dimesylate (LDX, Vyvanse), an approved treatment for attention-deficit/hyperactivity disorder. LDX is an inactive prodrug in which l-lysine is chemically bonded to d-amphetamine. Although its efficacy is not significantly different from that of other stimulants, LDX may be different with respect to potential toxicity and abuse liability. In this article, I will review the short-term controlled studies that were the basis for LDX's approval for both children and adults; the lack of and need for more long-term studies; two double-blind, placebo-controlled, crossover studies that examined LDX's abuse liability; and clinical uses for the drug. The clinical implications stemming from LDX's unique characteristics are also discussed.

Lisdexamfetamine

Lisdexamfetamine is an amphetamine prodrug, comprising an l-lysine amino acid covalently bonded to dextroamphetamine (d-amphetamine). Lisdexamfetamine is approved in the US for the treatment of attention-deficit hyperactivity disorder in children aged 6-12 years. Lisdexamfetamine is a therapeutically inactive molecule. After oral ingestion, lisdexamfetamine is hydrolyzed to l-lysine, a naturally occurring essential amino acid, and active d-amphetamine, which is responsible for the activity of the drug. In a well designed pharmacodynamic study in adult stimulant abusers, 50 or 100 mg doses of oral lisdexamfetamine had less likability than d-amphetamine 40 mg, suggesting a reduced abuse potential. Through rate-limited hydrolysis in the body, l-lysine is cleaved, gradually releasing pharmacologically active d-amphetamine. The pharmacokinetics of lisdexamfetamine suggest a reduced potential for abuse. In two well designed trials in children aged 6-12 years with attention-deficit hyperactivity disorder (ADHD), the efficacy of lisdexamfetamine was superior to that of placebo in improving symptoms associated with ADHD. Adverse events with lisdexamfetamine were, in general, mild to moderate in severity and consistent with those commonly reported with amphetamine.