Radiation Effects on Methamphetamine Pharmacokinetics and Pharmacodynamics in Rats.

BACKGROUND AND OBJECTIVES: Whole-body radiation exposure has been shown to alter the pharmacokinetics of certain drugs in both animal models and humans, but little is known about the effect of radiation on psychoactive medications. These drugs may have altered pharmacokinetics when administered during or after space travel or therapeutic or accidental radiation exposure, resulting in reduced efficacy or increased toxicity. METHODS: Methamphetamine was used to determine the effects of acutely administered 1, 3, and 6 Gy radiation on drug pharmacokinetics and pharmacodynamics. Male Wistar rats were exposed to 0, 1, 3, or 6 Gy X-ray radiation on day 0. The serum pharmacokinetics of subcutaneously administered 1 mg/kg methamphetamine was determined on day 3. Methamphetamine-induced (1 mg/kg) locomotor activity was measured on day 5. Brain methamphetamine concentrations were determined 2 h after methamphetamine administration (1 mg/kg) on day 6. Renal and hepatic serum biomarkers were assessed on days 3 and 6, with liver histology performed on day 6. RESULTS: While serum half-life and unchanged methamphetamine urine clearance were unaffected by any radiation dose, maximum methamphetamine concentrations and methamphetamine and amphetamine metabolite area under the serum concentration-time curve values from 0 to 300 min were significantly reduced after 6 Gy radiation exposure. Additionally, methamphetamine-induced locomotor activity and the brain to serum methamphetamine concentration ratio were significantly elevated after 6 Gy radiation. CONCLUSIONS: While 1-6 Gy radiation exposure did not affect methamphetamine elimination, 6 Gy exposure had effects on both subcutaneous absorption and brain distribution. These effects should be considered when administering drugs during or after radiation exposure.

Pharmacokinetics, Safety, and Tolerability of SHP465 Mixed Amphetamine Salts After Administration of Multiple Daily Doses in Children Aged 4-5 Years with Attention-Deficit/Hyperactivity Disorder.

BACKGROUND: Given the limited treatment options for younger children with attention-deficit/hyperactivity disorder (ADHD), a clinical study for SHP465 treatment was warranted. OBJECTIVES: We aimed to evaluate the pharmacokinetics, safety, and tolerability of SHP465 mixed amphetamine salts (MAS) 6.25 mg after multiple once-daily doses in children aged 4-5 years with ADHD. METHODS: In this open-label multicenter study, SHP465 MAS 6.25 mg once daily was administered for 28 days to children aged 4-5 years with ADHD; baseline ADHD Rating Scale-5 total score ≥ 28 (boys) or ≥ 24 (girls) and Clinical Global Impression-Severity scale score ≥ 4. Blood samples were collected in the pharmacokinetic-rich group predose on day 1 week 1 and day 7 week 4 (predose, postdose at 2, 5, 8, 12, 16, 24, and 48 hours); and in the pharmacokinetic-sparse group predose on day 1 weeks 1, 2, and 3 and 24 hours postdose on day 7 week 4 . Key pharmacokinetic parameters included maximum plasma drug concentration (Cmax), plasma trough drug concentration, time to Cmax during a dosing interval (tmax), area under the concentration-time curve from time 0 to time of last collected sample, area under the concentration-time curve over the dosing interval (24 h) at steady state (AUCtau,ss), first-order rate constant associated with the terminal phase of elimination, terminal half-life (t1/2), total clearance of drug from plasma after oral administration, and apparent volume of distribution at steady state. Safety endpoints included treatment-emergent adverse events and vital signs. RESULTS: Mean ± standard deviation age and body mass index of 24 participants (66.7% male) were 4.8 ± 0.41 years and 17.2 ± 3.18 kg/m2, respectively. The most common ADHD was the combined presentation (91.7%); ratings were 50% markedly ill and 45.8% moderately ill on the Clinical Global Impression-Severity scale. Plasma d-amphetamine and l-amphetamine steady state was attained by predose on treatment day 8, consistent with the half-life. Peak steady-state plasma concentration (median tmax) for both d-amphetamine and l-amphetamine occurred at 7.92 h postdose on day 7 week 4 and thereafter declined monoexponentially, with a geometric mean t1/2 of 10.4 and 12.3 h for d-amphetamine and l-amphetamine, respectively. For both d-amphetamine and l-amphetamine, Cmax and AUCtau,ss were comparable between children aged 4 years (n = 3) and children aged 5 years (n = 8) regardless of sex. In total, 14 treatment-emergent adverse events were reported by 45.8% (11/24) of participants. Five treatment-emergent adverse events, reported for four (16.7%) participants, were considered treatment related; affect lability occurred in two (8.3%) participants, and insomnia, accidental overdose, and increased blood pressure each occurred in one (4.2%) participant. CONCLUSIONS: In children aged 4-5 years with ADHD, following multiple once-daily administrations of SHP465 MAS 6.25 mg, the pharmacokinetic profile of plasma d-amphetamine and l-amphetamine was generally consistent among participants. Between-individual variability of plasma d-amphetamine and l-amphetamine steady-state exposure was low to moderate. SHP465 MAS was generally well tolerated in this study. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03327402 (31 October, 2017).

Single-Dose Pharmacokinetics of Amphetamine Extended-Release Oral Suspension in Healthy Adults.

Purpose: This single-dose pivotal study evaluated the pharmacokinetics of amphetamine extended-release oral suspension (AMPH EROS) under fasted and fed conditions and the relative bioavailability of AMPH EROS and immediate-release mixed amphetamine salts (IR MAS) in adults. Methods: This open-label, randomized, three-period, three-treatment, six-sequence crossover study enrolled 30 healthy adult participants who were randomly assigned to receive either 1 dose of AMPH EROS 18.8 mg under fed or fasted conditions or 30 mg of IR MAS under fasted conditions. Participants crossed over with a 7-day washout period between each of the three periods. Plasma samples were measured for Cmax, AUC0-t, AUC0-5, AUC5-t, and AUC0-∞ for comparative bioavailability. Results: The geometric mean ratios for Cmax, AUC0-t, and AUC0-∞ were within the 90% confidence limits [80.0%, 125.0%] for comparable bioavailability. There was no food effect for AMPH EROS. Both the AMPH EROS and IR MAS formulations were generally well tolerated with no serious adverse events reported. Conclusions: The bioavailability of a single dose of AMPH EROS was comparable to two 15 mg doses of IR MAS, given 4 hr apart, with no food effect or safety concerns observed.

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.

Relationship Between Amphetamine Concentrations in Saliva and Serum in Children and Adolescents With Attention-Deficit/Hyperactivity Disorder.

BACKGROUND: Therapeutic drug monitoring (TDM) is a valid tool for the optimization of psychopharmacotherapy; however, in child and adolescent psychiatry, uncomfortable intravenous sample collection is the main challenge and restricts the use of TDM. Therefore, it is important to evaluate alternate specimens to facilitate TDM. The aim of this study was to evaluate the feasibility of using saliva for the TDM of amphetamine in children and adolescents with attention-deficit/hyperactivity disorder. METHODS: In this study, 28 patient samples (mean age, 11.3 years; boys, 23; and girls, 5) treated with lisdexamfetamine were included. The active compound amphetamine was extracted and derivatized before quantification by high-performance liquid chromatography with fluorescence detection. Nonparametric Spearman rank correlations were used for correlation analyses; for clinical validation, Bland-Altman analysis was applied. RESULTS: The median amphetamine concentrations in saliva were 2.7 times higher (range 0.7-23.6) than those in serum (257.8 ng/mL versus 77.2 ng/mL; z = -4.51, P < 0.001). A strong positive linear correlation was observed between saliva and serum concentrations (ρ = 0.628, P < 0.001). The ratio of saliva-to-serum concentration was strongly pH dependent (ρ = -0.712, P < 0.001). Therefore, a transformation formula, factoring in salivary pH, to calculate serum concentrations from the measured saliva concentrations was applied. Theoretical and measured serum amphetamine concentrations were subjected to Bland-Altman analysis. Using an acceptance limit of 20%, only 21% (n = 6) of samples fulfilled this criterion. CONCLUSIONS: Amphetamine paired saliva-to-serum concentrations were highly variable and strongly affected by salivary pH, indicating that saliva is an inappropriate sampling matrix for TDM of amphetamine. Furthermore, Bland-Altman analysis did not support saliva as a suitable matrix for TDM.

Mechanistic PBPK Modeling of Urine pH Effect on Renal and Systemic Disposition of Methamphetamine and Amphetamine.

The effect of urine pH on renal excretion and systemic disposition has been observed for many drugs and metabolites. When urine pH is altered, tubular ionization, passive reabsorption, renal clearance, and systemic exposure of drugs and metabolites may all change dramatically, raising clinically significant concerns. Surprisingly, the urine pH effect on drug disposition is not routinely explored in humans, and regulatory agencies have neither developed guidance on this issue nor required industry to conduct pertinent human trials. In this study, we hypothesized that physiologically based pharmacokinetic (PBPK) modeling could be used as a cost-effective method to examine potential urine pH effect on drug and metabolite disposition. Our previously developed and verified mechanistic kidney model was integrated with a full-body PBPK model to simulate renal clearance and area under the plasma concentration-time curve (AUC) with varying urine pH statuses using methamphetamine and amphetamine as model compounds. We first developed and verified drug models for methamphetamine and amphetamine under normal urine pH condition [absolute average fold error (AAFE) < 1.25 at study level]. Then, acidic and alkaline urine scenarios were simulated. Our simulation results show that the renal excretion and plasma concentration-time profiles for methamphetamine and amphetamine could be recapitulated under different urine pH (AAFE < 2 at individual level). The methamphetamine-amphetamine parent-metabolite full-body PBPK model also successfully simulated amphetamine plasma concentration-time profiles (AAFE < 1.25 at study level) and amphetamine/methamphetamine urinary concentration ratios (AAFE < 2 at individual level) after dosing methamphetamine. This demonstrates that our mechanistic PBPK model can predict urine pH effect on systemic and urinary disposition of drugs and metabolites. SIGNIFICANCE STATEMENT: Our study shows that integrating mechanistic kidney model with full-body physiologically based pharmacokinetic model can predict the magnitude of alteration in renal excretion and area under the plasma concentration-time curve (AUC) of drugs and metabolites when urine pH is changed. This provides a cost-effective method to evaluate the likelihood of renal and systemic disposition changes due to varying urine pH. This is important because multiple drugs and diseases can alter urine pH, leading to quantitatively and clinically significant changes in drug and metabolite disposition that may require adjustment of therapy.

Single-dose pharmacokinetics of amphetamine extended-release tablets compared with amphetamine extended-release oral suspension.

OBJECTIVE: Evaluate the relative bioavailability of single-dose amphetamine extended-release tablet (AMPH ER TAB) 20 mg, swallowed whole or chewed, and amphetamine extended-release oral suspension (AMPH EROS) 2.5 mg/mL; evaluate food effect on AMPH ER TAB. METHODS: Healthy volunteers (18-55 years) were randomized to 1 dose of AMPH ER TAB 20 mg swallowed (fasted), chewed (fed/fasted), or 20 mg AMPH EROS (fasted). A crossover study design was used. Plasma samples were collected each period predose and at time points to 60 hours postdose. d- and l-amphetamine were measured and pharmacokinetic (PK) was calculated (90% confidence intervals of the ratios of the plasma levels) for AUC0-t, AUC0-∞, and Cmax. Comparative relative bioavailability between formulations was determined when ratios were within 80% and 125%. Safety was also assessed. RESULTS: Thirty-two subjects completed the study. AMPH ER TAB swallowed versus AMPH EROS (fasted): for d- and l-amphetamine, the total and peak exposure was similar: d: AUC0-t: 100.68% to 108.08%, AUC0-∞: 101.47% to 109.52%, Cmax: 98.10% to 103.17%; l: AUC0-t: 100.31% to 108.57%, AUC0-∞: 101.27% to 111.09%, Cmax: 98.2% to 103.37%. For d- and l-amphetamine when the tablet is swallowed whole, Tmax was 5.00 hours (with a range of 2.00-9.00 hours). AMPH ER TAB chewed versus AMPH EROS (fasted): for d- and l-amphetamine, the total and peak exposure was similar: d: AUC0-t: 99.23% to 106.62%, AUC0-∞: 99.58% to 107.59%, Cmax: 99.91% to 105.14%; l: AUC0-t: 98.16% to 106.35%, AUC0-∞: 98.44% to 108.11%, Cmax: 99.53% to 104.75%. For d- and l-amphetamine when the tablet has been chewed, Tmax was 5.00 hours (with a range of 3.00-7.00 hours). PK results were similar for patients in the fasted and fed groups, indicative of no presence of food effect. No serious adverse events (AEs) were reported, overall AE profiles between the tablet and oral suspension were comparable without any unanticipated safety concerns. CONCLUSIONS: Single doses of AMPH ER TAB for both d- and l-amphetamine demonstrated comparable bioavailability to a 20 mg dose of AMPH EROS, 2.5 mg/mL under fasted conditions when chewed and swallowed whole, and demonstrated equivalent peak and overall exposure without apparent food effect. AMPH ER TAB was well-tolerated and consistent with adverse events noted in other amphetamine formulations.

An Open-Label, Multicenter, Single-Dose Pharmacokinetic Study of a Novel Amphetamine Extended-Release Orally Disintegrating Tablet in Preschool-Aged Children.

Objective: In the U.S. ∼33% of children with attention-deficit/hyperactivity disorder (ADHD) are diagnosed during their preschool years (<6 years of age). The majority of these children are treated with a psychopharmacological treatment, despite limited data on pharmacokinetics (PKs), efficacy, or safety of these medications in this population. A phase 4, single-dose open-label study was conducted to assess the PK profile of amphetamine extended-release orally disintegrating tablets (AMP XR-ODT) under fasted conditions in preschool-aged children with ADHD. Methods: Preschool-aged children (aged 4 to <6 years) with a confirmed ADHD diagnosis were enrolled and administered AMP XR-ODT 3.1 mg under fasted conditions. Plasma samples were analyzed for d- and l-amphetamine (AMP) via liquid chromatography-tandem mass spectrometry. Area under the concentration-time curve from time 0 extrapolated to infinity (AUC0-inf), area under the concentration-time curve from time 0 to the last measurable plasma concentration (AUC0-T), maximum plasma concentration (Cmax), time to maximum plasma concentration (Tmax), terminal half-life (t1/2), apparent volume of distribution (Vz/F), and apparent clearance (CL/F) for d- and l-AMP and safety were assessed. Results: The PK and safety analyses included 15 preschool-aged children (4 years old, n = 6; 5 years old, n = 9); 14 completed the study. Quantifiable plasma concentrations for d- and l-AMP were observed 1.5 hours postdose and throughout the 24-hour sampling period. For d- and l-AMP, mean AUC0-inf was 315.2 and 104.4 h·ng/mL, AUC0-T was 296.0 and 96.8 h·ng/mL, t1/2 was 8.0 and 9.2 hours, Cmax was 23.0 and 7.0 ng/mL, Tmax was 3.9 and 4.0 hours, CL/F was 6996.3 and 6837.1 mL/h, and Vz/F was 75,874.5 and 84,140.0 mL, respectively. Adverse events included tachycardia (n = 2), neutropenia (n = 1), increased alanine aminotransferase (n = 1), and aspartate aminotransferase (n = 1). Conclusions: AMP XR-ODT 3.1 mg was well tolerated in preschool-aged children, with detectable plasma AMP concentrations over 24 hours, and a PK profile consistent with once-daily dosing.

Pharmacokinetics of AR19, an Immediate-Release Amphetamine Sulfate Formulation Designed to Deter Manipulation for Administration Via Nonoral Routes: Bioequivalence to Reference Racemic Amphetamine Sulfate, Dose Proportionality, and Food Effect.

Objectives: We evaluated the pharmacokinetics (PK) of an investigational immediate-release amphetamine (AMP) sulfate formulation (AR19) designed to deter nonoral administration versus reference racemic amphetamine sulfate (RA-AMPH). We investigated AMP bioavailability from AR19, the effect of taking AR19 with food or sprinkling the capsules on food, and dose proportionality. Methods: Participants received AR19 (20 mg) or reference RA-AMPH (20 mg) (bioequivalence study) or AR19 5 or 30 mg (dose comparison study). Food effect study participants received AR19 (20 mg) as intact capsule while fasted or after high-fat/-calorie meal, or as pellets sprinkled on applesauce or yogurt (≥6-day washout). Blood samples were analyzed for dextroamphetamine (d-AMP) and levoamphetamine (l-AMP) PK: Cmax, AUClast, AUCinf, λz, T½, and Tmax. Safety was assessed. Results: Bioequivalence, dose comparison, and food effect studies included 36, 24, and 36 participants. The 90% confidence intervals (CIs) of Cmax, AUClast, and AUCinf for AR19 20 mg versus reference RA-AMPH or AR19 with intact capsule and meal or sprinkled AR19 pellets on food versus fasted were between 80% and 125%. Dose-normalized Cmax/D, AUClast/D, and AUCinf/D for AR19 5 versus 30 mg had CIs within 80%-125%. Mean ± standard deviation (SD) Tmax was comparable for AMP (d-AMP; l-AMP) following AR19 20 mg (2.84 ± 1.05; 3.05 ± 1.22) versus reference RA-AMPH (2.52 ± 0.75; 2.75 ± 1.00), and AR19 5 mg (2.48 ± 0.57; 2.65 ± 0.65) versus AR19 30 mg (2.55 ± 0.56; 2.72 ± 0.65). Mean ± SD Tmax for AMP (d-AMP; l-AMP) was higher with intact capsule and meal (5.59 ± 1.57; 5.59 ± 1.59) versus fasted (2.85 ± 0.76; 2.97 ± 0.79). No serious adverse events were reported. Conclusion: AR19 was bioequivalent to reference RA-AMPH. Bioavailability was similar at doses between 5 and 30 mg and was not impacted by meal consumption or sprinkling on food. AR19 at tested doses was 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.

Amphetamine extended-release oral suspension for attention-deficit/hyperactivity disorder.

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder known to respond to amphetamine (AMPH). Multiple AMPH formulations have been developed during the past two decades and have focused mainly on extending the duration of effect. AMPH extended-release oral suspension, Dyanavel XR, (AMPH EROS) was developed to address the unmet needs of patients who have difficulty swallowing intact extended-release (ER) tablets and capsules. Areas covered: The pharmacokinetic profile of the AMPH EROS in children and adults is discussed along with the technology responsible for its release profile. Efficacy data from two clinical trials are presented and AMPH EROS is compared with other marketed AMPH ER formulations in the United States. Expert opinion: Multiple AMPH ER formulations that do not require ingestion of an intact tablet or capsule have been developed. Initial products allowed for sprinkling or dissolving of capsule contents. Recently, oral disintegrating tablets, chewable tablets, and oral suspensions have been marketed. Each formulation has positive attributes. Tablets may be more portable. However, as a suspension, AMPH EROS dosing can differ depending on daily requirements. Dose can also be titrated with a single prescription. Despite its convenience, AMPH EROS is a branded product, so price may be prohibitive for some patients.

New Formulations of Stimulants: An Update for Clinicians.

In the last 15 years, there has been a marked increase in the number of available stimulant formulations with the emphasis on long-acting formulations, and the introduction of several novel delivery systems such as orally dissolving tablets, chewable tablets, extended-release liquid formulations, transdermal patches, and novel "beaded" technology. All of these formulations involve changes to the pharmaceutical delivery systems of the two existing compounds most commonly employed to treat attention-deficit/hyperactivity disorder (ADHD), amphetamine (AMP) and methylphenidate (MPH). In addition to these new formulations, our knowledge about the individual differences in response has advanced and contributes to a more nuanced approach to treatment. The clinician can now make increasingly informed choices about these formulations and more effectively individualize treatment in a way that had not been possible before. In the absence of reliable biomarkers that can predict individualized response to ADHD treatment, clinical knowledge about differences in MPH and AMP pharmacodynamics, pharmacokinetics, and metabolism can be utilized to personalize treatment and optimize response. Different properties of these new formulations (delivery modality, onset of action, duration of response, safety, and tolerability) will most likely weigh heavily into the clinician's choice of formulation. To manage the broad range of options that are now available, clinicians should familiarize themselves in each of these categories for both stimulant compounds. This review is meant to serve as an update and a guide to newer stimulant formulations and includes a brief review of ADHD and stimulant properties.

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.

Pharmacokinetics of selegiline, R-methamphetamine, R-amphetamine, and desmethylselegiline in oral fluid after a single oral administration of selegiline.

BACKGROUND: Chiral analysis is a crucial way to differentiate selegiline (SG) intake from drug abuse. Oral fluid (OF) has been successfully used as an alternative matrix for blood testing in several pharmacokinetic studies. OBJECTIVE: The aim of this study is to describe the pharmacokinetics of SG and its main metabolites in OF after a single oral administration of SG which is meaningful for results interpretation in forensic analysis. METHODS: Ten milligrams of SG were orally administered to 8 volunteers, and OF samples were collected for up to 96 hours by having participants spit into polypropylene tubes without stimulation. These samples were submitted to liquid-liquid extraction before analysis by liquid chromatography-tandem mass spectrometry operating in positive ion multiple-reaction monitoring mode. RESULTS AND CONCLUSIONS: After oral administration, each analyte could be detected in OF specimens from all volunteers with an initial detection time of 0.50 hours. The Cmax values of SG, R-MA, R-AM and DM-SG were 50.93-992.67 ng/mL, 29.78-653.64 ng/mL, 8.22-150.15 ng/mL, and 4.34-16.25 ng/mL, respectively, at 0.5 hours, 1-11 hours, 1.5-11 hours, and 0.5-6 hours post dose. The times when the compounds were last determined in OF were 5-24 hours for SG, 52-96 hours for R-MA, 31-96 hours for R-AM, and 13-31 hours for DM-SG after oral administration. There is a period of time in OF in which only MA and AM are present without SG and DM-SG after a single dose of SG. The pharmacokinetic data could provide supplementary interpretation for OF tests in forensic science and drug treatment programs.

Pharmacokinetics of a New Amphetamine Extended-Release Oral Suspension in Children with Attention-Deficit/Hyperactivity Disorder.

OBJECTIVE: An extended-release amphetamine (AMP) oral suspension has been developed to facilitate medication ingestion and dose titration. This study sought to determine the pharmacokinetic (PK) profile of this new formulation in children with attention-deficit/hyperactivity disorder (ADHD). METHODS: This was an open-label, single-period, PK study in 29 pediatric participants with ADHD. Participants were stratified into age groups 1 (6-7 years), 2 (8-9 years), and 3 (10-12 years), and dosed with 15 mL extended-release AMP liquid suspension (equivalent to 30 mg mixed AMP salts) after an overnight fast. Blood samples were collected at prespecified time points and analyzed for d- and l-AMP concentrations. Key PK parameters included maximum plasma concentration (Cmax), time to maximum plasma concentration, half-life (T1/2), area under the curve from time 0 to last quantifiable concentration (AUClast) and to infinity (AUCinf), oral clearance (CL/F), and volume of distribution (Vz/F). The 95% confidence intervals (CIs) about the geometric means of the weight-normalized CL/F, Vz/F, and AUClast were determined. Safety was also assessed. RESULTS: All participants completed the study. As age increased, mean maximum and total exposure to AMP decreased; weight-normalized CL/F slightly increased, resulting in decreasing T1/2 values with age. For d- and l-AMP, the 95% CIs for the geometric means of weight-normalized CL/F/kg and Vz/F/kg were within the 60%-140% range for groups 2 and 3, while those of weight-normalized AUClast were within range for all age groups. Adverse events were mild and consistent with the safety profile of AMP. CONCLUSIONS: Exposure (Cmax, AUCinf, and AUClast) to AMP decreased with age, possibly as a result of the 30-mg/15-mL fixed dose across a range of weights (20-57 kg) and the consequent lower dose per kilogram in older participants, as well as the slight increase in clearance with age.

Pharmacokinetics of a New Amphetamine Extended-release Oral Liquid Suspension Under Fasted and Fed Conditions in Healthy Adults: A Randomized, Open-label, Single-dose, 3-treatment Study.

PURPOSE: A new amphetamine extended-release liquid formulation (AMP XR-OS), intended for the treatment of attention-deficit/hyperactivity disorder, has been developed. This study was performed to determine if administration with food affected the rate of absorption or bioavailability of AMP XR-OS. The formulation was also compared with an equivalent dose of an extended-release mixed amphetamine salts reference product (30 mg) under fed conditions. METHODS: Thirty adult volunteers participated in this single-dose, open-label, randomized, 3-period, 3-treatment crossover study. Each participant received a single 15-mL dose of AMP XR-OS (equivalent to 30 mg of the reference drug) under fasted conditions, a single 15-mL dose of AMP XR-OS under fed conditions, and a single dose of the reference drug under fed conditions. A 7-day washout separated the 3 treatment periods. Blood samples were collected at predetermined time points and analyzed for d- and l-amphetamine. Pharmacokinetic parameters reported are AUC0-5, AUC0-last, AUC5-last, and AUC0-∞; Cmax; elimination t1/2; and Tmax. The geometric mean ratios and 90% CIs of Cmax, AUC0-last, and AUC0-∞were determined for the comparison of AMP XR-OS fed and fasted, and Cmax, AUC0-5, AUC5-last, and AUC0-∞ were calculated for AMP XR-OS compared with the reference drug under fed conditions. Safety was also assessed. FINDINGS: Twenty-nine subjects completed the study. Subjects were mostly male, white, and of Hispanic/Latino ethnicity with a mean age of 35.83 years and a mean BMI of 25.36kg/m2. The 90% CIs of Cmax, AUC0-last, and AUC0-∞ for AMP XR-OS fasted versus fed were within the accepted 80% to 125% range, indicating lack of a food effect. In the comparison of AMP XR-OS fed versus the reference product, Cmax, AUC5-last, and AUC0-∞ were within the range to establish bioequivalence; however, AUC0-5 was significantly higher for AMP XR-OS compared with that of the reference drug. This difference between products was likely due to the known delay of Tmax and decreased exposure when the extended-release mixed amphetamine salts reference product is administered with food. A total of 36 mild or moderate adverse events were reported; 1 subject withdrew due to an adverse event, and no deaths occurred. These adverse events were consistent with the known pharmacodynamic effects of amphetamine. IMPLICATIONS: The absence of a food effect may allow for AMP XR-OS to be administered with or without a meal.

A Randomized Phase I Study to Assess the Effect of Alcohol on the Pharmacokinetics of an Extended-release Orally Disintegrating Tablet Formulation of Amphetamine in Healthy Adults.

PURPOSE: There is a strong association between attention-deficit/hyperactivity disorder (ADHD) and alcohol abuse, yet no studies have systematically assessed the effect of alcohol on the pharmacokinetics of psychostimulants such as amphetamine (AMP) in vivo. This study evaluated the effects of alcohol on the rate and extent of absorption of Adzenys™ XR-ODT*, a new extended-release orally disintegrating AMP tablet (AMP XR-ODT) for ADHD. METHODS: A Phase I single-dose, open-label study was conducted in 32 healthy adults. Participants were split into 2 cohorts, allowing for close monitoring of safety profile and tolerability, and were randomized 1:1:1:1 to receive treatment in 1 of 4 sequences. Each treatment included the administration of a single 18.8-mg dose of AMP XR-ODT, followed by 240 mL of deionized water or 4%, 20%, or 40% ethanol. Blood samples were collected at prespecified time points. The pharmacokinetic profiles of d- and l-AMP were comparable across treatment groups. FINDINGS: There was no change in the extent of absorption for d- or l-AMP with alcohol coingestion and no dose dumping of the extended-release portion of the formulation. The 90% CIs for the geometric mean ratios (4%, 20%, and 40% ethanol versus water) for Cmax and systemic exposure (AUC0-5, AUClast, and AUC0-∞) were within 80% to 125%. Adverse events were mild to moderate and were consistent with the known adverse event profile for AMP XR-ODT or alcohol. IMPLICATIONS: Varying concentrations of alcohol (4%-40%) did not significantly alter the pharmacokinetic profile of AMP XR-ODT. These findings are relevant to clinicians who have concerns about alcohol use and/or abuse when treating ADHD.

Medico-legal assessment of methamphetamine and amphetamine serum concentrations-what can we learn from survived intoxications?

Medico-legal experts are increasingly enlisted to assess the methamphetamine and amphetamine serum concentrations after a criminal offense. However, since criminal users rarely provide useful information to medico-legal experts regarding the substances abused, when the substance(s) was/were used, dose of ingestion tools are needed to interpret the analytical data, which can be used as objective evidence in such cases. A comparative series of methamphetamine and amphetamine serum concentrations were used to analyze the frequency of concentrations, to determine methamphetamine/amphetamine concentration ratios, and prove them as a tool to distinguish pure methamphetamine from mixed amphetamine/methamphetamine ingestion. Additionally, two cases of survived accidental methamphetamine intoxication, resulting from ingestion smuggling which was longitudinally monitored, and pharmacokinetic parameters were assessed. In a series of 628 samples where the most frequent concentration of methamphetamine exceeded the therapeutic level, there was a strong correlation suggesting pure methamphetamine consumption, when the ratios of methamphetamine/amphetamine concentrations were within the range between 3 and 10. In the two cases of methamphetamine bodypacking, the relevant serum concentrations of methamphetamine and amphetamine, which could be measured up to 9 days after ingestion, indicated a decrease of the methamphetamine/amphetamine ratios in an exponential manner. However, the ratios were not always within the range between 3 and 10. Lastly, the course of the serum concentrations suggested an increase of the apparent elimination half-life of methamphetamine. In terms of the objective evidence required in criminal law, calculating methamphetamine/amphetamine concentration ratio is not a suitable to means to distinguish pure methamphetamine intake and that of mixed amphetamine/methamphetamine abuse in an individual case. Instead, methamphetamine high serum concentrations and the possible increase in apparent elimination half-life suggest that an extended detection period may be used to distinguish between "illicit use" as compared to "therapeutic use" of methamphetamine.

Pharmacokinetics of a Novel Amphetamine Extended-Release Orally Disintegrating Tablet in Children with Attention-Deficit/Hyperactivity Disorder.

BACKGROUND: A novel formulation for treating attention-deficit/hyperactivity disorder (ADHD) has recently been developed-amphetamine extended-release orally disintegrating tablets (AMP XR-ODTs). In this study, we assessed the rate of absorption and exposure of AMP XR-ODT under fasted conditions in children with ADHD. METHODS: Children (6-12 years) with ADHD were enrolled in a single-dose, open-label, single-period pharmacokinetic (PK) study. Patients were stratified by age (6-7, 8-9, and 10-12 year olds) and were dosed with 18.8-mg AMP XR-ODT under fasted conditions. Plasma samples were analyzed for d-and l-amphetamine. Maximum plasma concentration (Cmax), time to maximum plasma concentration (Tmax), area under the concentration-time curve from time zero-infinity (AUCinf), weight-normalized clearance (CL/F), and weight-normalized volume of distribution (Vz/F) were assessed. The geometric mean and 95% confidence intervals (CIs) were calculated for weight-normalized CL/F and Vz/F in each age group to determine if the 95% CIs were within the target range of 60%-140%. RESULTS: A total of 28 children completed the study. The 95% CIs for the geometric mean CL/F/kg and Vz/F/kg for both d- and l-amphetamine fell within the target range of 60%-140% for each age group, thus meeting the primary end point. Four participants experienced treatment-related adverse events, including vomiting (n = 3), abdominal pain (n = 2), dry mouth (n = 1), and insomnia (n = 1). CONCLUSIONS: AMP XR-ODT, a novel formulation that does not require swallowing an intact tablet or capsule, was well tolerated and demonstrated a PK profile consistent with once-daily dosing in children with ADHD.