Pharmacokinetics of Long-Acting Methylphenidate: Formulation Differences, Bioequivalence, Interchangeability

BACKGROUND AND OBJECTIVE: Attention deficit hyperactivity disorder is one of the most common neuropsychiatric conditions in children, and methylphenidate (MPH) is one of the first-line therapies. MPH is available in a variety of extended-release (ER) formulations worldwide, and most formulations are not considered bioequivalent due to differences in pharmacokinetics. It is hypothesized that the current bioequivalence guidelines from the different regulatory bodies may generate inconsistent findings or recommendations when assessing the bioequivalence of ER MPH formulations. This manuscript aims to conduct a comprehensive and narrative critical literature review to analyze pharmacokinetic data pertaining to ER formulations of MPH in order to assess bioequivalence, differences in regulatory guidelines, and additional pharmacokinetic-pharmacodynamic parameters that may help define interchangeability.

METHODS

A literature search was conducted in EMBASE, Medline, and Cochrane Library with no time limits. Study characteristics, non-compartmental pharmacokinetic parameters, and bioequivalence data were extracted for analysis.

RESULTS

Thirty-three studies were identified with primary pharmacokinetic data after the administration of ER MPH, of which 10 were direct comparative studies (i.e., at least 2 formulations tested within a single setting) and 23 were indirect comparisons (i.e., different experimental settings). Two formulations were consistently reported as bioequivalent across the regulatory bodies using criteria from their guidance documents, although inconsistencies have been observed. However, when additional kinetic criteria (discussed in this manuscript) were imposed, only one study met the more stringent definition of bioequivalence. Various clinical factors also had inconsistent effects on the pharmacokinetics and interchangeability of the different formulations, which were associated with a lack of standardization for assessing covariates across the regulatory agencies.

CONCLUSION

Additional pharmacokinetic parameters and consistency in guidelines across the regulatory bodies may improve bioequivalence assessments. Based on our findings, more research is also required to understand whether bioequivalence is an appropriate measure for determining MPH interchangeability. This critical review is suitable for formulation scientists, clinical pharmacologists, and clinicians.

Modeling Developmental Changes in Caffeine Clearance Considering Differences between Pre- and Postnatal Period

Taguchi et al. reported that postmenstrual age (PMA) is a promising factor in describing and understanding the developmental change of caffeine (CAF) clearance. The aim of the present study was to quantify how developmental changes occur and to determine the effect of the length of the gestational period on CAF clearance. We performed a nonlinear mixed effect model (NONMEM) analysis and evaluated the fit of six models. A total of 115 samples were obtained from 52 patients with a mean age of 34.3 ± 18.2 d. The median values of gestational age (GA) and postnatal age (PNA) were 196 and 31 d, respectively. Serum CAF levels corrected for dose per body surface area (BSA) (C/D ratioBSA) were dependent on PMA rather than PNA, which supports the findings of a previous study. NONMEM analysis provided the following final model of oral clearance: CL/F = 0.00603∙WT∙∙0.877GA ≤ 196 L/h. This model takes into account developmental changes during prenatal and postnatal periods separately. The model successfully described the variation in clearance of CAF. Our findings suggest that the dosage of CAF in preterm infants should be determined based not only on body weight (WT) but also on both PNA and GA.

Modafinil, an atypical CNS stimulant?

Modafinil is a central nervous system stimulant approved for the treatment of narcolepsy and sleep disorders. Due to its wide range of biochemical actions, modafinil has been explored for other potential therapeutic uses. Indeed, it has shown promise as a therapy for cognitive disfunction resulting from neurologic disorders like ADHD, and as a smart drug in non-medical settings. The mechanism(s) of actions underlying the therapeutic efficacy of this agent remains largely elusive. Modafinil is known to inhibit the dopamine transporter, thus decreasing dopamine reuptake following neuronal release, an effect shared by addictive psychostimulants. However, modafinil is unique in that only a few cases of dependence on this drug have been reported, as compared to other psychostimulants. Moreover, modafinil has been tested, with some success, as a potential therapeutic agent to combat psychostimulant and other substance use disorders. Modafinil has additional, but less understood, actions on other neurotransmitter systems (GABA, glutamate, serotonin, norepinephrine, etc.). These interactions, together with its ability to activate selected brain regions, are likely one of the keys to understand its unique pharmacology and therapeutic activity as a CNS stimulant. In this chapter, we outline the pharmacokinetics and pharmacodynamics of modafinil that suggest it has an "atypical" CNS stimulant profile. We also highlight the current approved and off label uses of modafinil, including its beneficial effects as a treatment for sleep disorders, cognitive functions, and substance use disorders.

Effect of Colonic Absorption on the Pharmacokinetic Properties of Delayed-Release and Extended-Release Methylphenidate: In Vivo, In Vitro, and Modeling Evaluations

Most stimulants used to treat attention‐deficit/hyperactivity disorder are administered in the morning and absorbed in the upper gastrointestinal tract. DR/ER‐MPH (formerly HLD200), an evening‐dosed delayed‐release and extended‐release methylphenidate, is predicted to be absorbed in the proximal colon. The pharmacokinetic (PK) profile of DR/ER‐MPH is characterized by an 8‐ to 10‐hour delay in initial methylphenidate absorption and a subsequent gradual increase in plasma concentration, followed by a slow decline. To examine the relationship of absorption site to pharmacokinetics, the DR/ER‐MPH formulation was altered to release methylphenidate in the small intestine and distal colon. The 3 formulations were administered in an open‐label, 3‐way, crossover study in healthy adults (N = 18). Compared with the small intestine formulation, the PK profile of the proximal colon (DR/ER‐MPH) formulation exhibited a longer delay before initial methylphenidate absorption, decreased peak methylphenidate concentration, increased time to peak concentration, and decreased bioavailability; these characteristics were amplified in the distal colon formulation. Safety profiles fell within the expectations for methylphenidate products. Modeled PK profiles were similar between the small intestine formulation and a morning‐dosed extended‐release methylphenidate (both predicted to release methylphenidate in the upper gastrointestinal tract), providing additional evidence that the PK profile of DR/ER‐MPH is shaped by colonic absorption.

Comparative Neuropharmacology and Pharmacokinetics of Methamphetamine and Its Thiophene Analog Methiopropamine in Rodents

Methiopropamine is a novel psychoactive substance (NPS) that is associated with several cases of clinical toxicity, yet little information is available regarding its neuropharmacological properties. Here, we employed in vitro and in vivo methods to compare the pharmacokinetics and neurobiological effects of methiopropamine and its structural analog methamphetamine. Methiopropamine was rapidly distributed to the blood and brain after injection in C57BL/6 mice, with a pharmacokinetic profile similar to that of methamphetamine. Methiopropamine induced psychomotor activity, but higher doses were needed (E_max 12.5 mg/kg; i.p.) compared to methamphetamine (E_max 3.75 mg/kg; i.p.). A steep increase in locomotor activity was seen after a modest increase in the methiopropamine dose from 10 to 12.5 mg/kg, suggesting that a small increase in dosage may engender unexpectedly strong effects and heighten the risk of unintended overdose in NPS users. In vitro studies revealed that methiopropamine mediates its effects through inhibition of norepinephrine and dopamine uptake into presynaptic nerve terminals (IC₅₀ = 0.47 and 0.74 µM, respectively), while the plasmalemmal serotonin uptake and vesicular uptake are affected only at high concentrations (IC₅₀ > 25 µM). In summary, methiopropamine closely resembles methamphetamine with regard to its pharmacokinetics, pharmacodynamic effects and mechanism of action, with a potency that is approximately five times lower than that of methamphetamine.

Pharmacokinetics of Synthetic Cathinones Found in Bath Salts in Mouse Brain and Plasma Using High-Pressure Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND AND OBJECTIVES

Approximately 10 years ago, "bath salts" became popular as legal alternatives to the psychostimulants cocaine and the amphetamines. These products contained synthetic cathinones, including 3,4-methylenedioxypyrovalerone (MDPV), 4-methylmethcathinone (mephedrone), and 3,4-methylenedioxymethcathinone (methylone). Most preclinical investigations have only assessed the effects of these synthetic cathinones independently; however, case reports and Drug Enforcement Administration (DEA) studies indicate that bath salts contain mixtures of these substances. In this study, we examine the pharmacokinetic interactions of the drug combination. We hypothesized that combined exposure to MDPV, mephedrone, and methylone would result in increased drug concentrations and enhanced total drug concentrations when compared to individual administration.

METHODS

Adolescent male Swiss-Webster mice were injected intraperitoneally with either 10 mg/kg MDPV, 10 mg/kg mephedrone, 10 mg/kg methylone, or 10 mg/kg combined MDPV, mephedrone, and methylone. Following injection, brains and plasma were collected at 1, 10, 15, 30, 60, and 120 min. Drugs were extracted via solid-phase extraction, and concentrations were determined using a previously published high-pressure liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method.

RESULTS

All drugs crossed the blood-brain barrier quickly. For methylone, the maximal concentration (C_max) and the total drug exposure [as represented by the area under the concentration-time curve (AUC)] were significantly higher when combined with mephedrone and MDPV in both matrices (2.89-fold increase for both C_max and AUC with combined treatment). For mephedrone, the C_max was unchanged, but the AUC in brain was increased when in combination by approximately 34%. Interestingly, for MDPV, the C_max was unchanged, yet the AUC was higher when MDPV was administered individually (there was a 62% decrease in AUC with combined treatment).

CONCLUSIONS

The pharmacokinetics of methylone, mepedrone, and MDPV are altered when the drugs are used in combination. These data provide insight into the consequences of co-exposure to synthetic cathinones in popular bath salt products.

Pharmacokinetics of Coadministered Viloxazine Extended-Release (SPN-812) and Lisdexamfetamine in Healthy Adults

BACKGROUND

Viloxazine extended-release is a novel nonstimulant under investigation as a potential treatment for attention-deficit/hyperactivity disorder (ADHD). Given the potential for viloxazine extended-release to be co-administered with stimulant ADHD pharmacotherapies, this trial investigated the pharmacokinetics and safety of combination viloxazine extended-release + lisdexamfetamine dimesylate (lisdexamfetamine) versus viloxazine extended-release and lisdexamfetamine alone.

METHODS

In this single-center, cross-over, open-label trial, healthy, non-ADHD adults received single oral doses of 700 mg viloxazine extended-release alone, 50 mg lisdexamfetamine alone, and a combination of viloxazine extended-release (700 mg) + lisdexamfetamine (50 mg), with blood samples collected over 4 days postadministration. The active drug in viloxazine extended-release (viloxazine) and primary metabolite of lisdexamfetamine (d-amphetamine) were measured using chromatographic tandem mass spectrometry. Safety assessments included adverse events, vital signs, echocardiograms, and clinical laboratory evaluations.

RESULTS

Thirty-six adults were enrolled, and 34 completed the trial. The least squares geometric mean ratios are reported as [combination / single drug (90% confidence intervals)]. Viloxazine extended-release: Cmax = 95.96% (91.33-100.82), area under the concentration-time curve from 0 to the last measurable time (AUC0-t) = 99.19% (96.53-101.91), and area under the concentration-time curve from 0 to infinity (AUCinf) = 99.23% (96.61-101.93). Lisdexamfetamine: Cmax = 112.78% (109.93-115.71), AUC0-t = 109.64% (105.25-114.22), and AUCinf = 109.52% (105.19-114.03). All reported adverse events, except 1 (moderate vomiting), were mild in severity.

CONCLUSIONS

Co-administration of viloxazine extended-release and lisdexamfetamine did not impact the pharmacokinetics of viloxazine or d-amphetamine relative to administration of either drug alone. After single dose administration, the combination appeared to be safe and well tolerated.

Effect of bile duct ligation-induced liver dysfunction on methamphetamine pharmacokinetics in male and female rats

BACKGROUND

Several disease states commonly associated with methamphetamine (METH) use produce liver dysfunction, and in the bile duct ligation (BDL) model of hepatic dysfunction, rats with liver injury are more sensitive to METH effects. Additionally, both female rats and humans are known to be more sensitive to METH than males. In consideration of known sex-dependent differences in METH pharmacokinetics, this study sought to determine the potential interaction between sex and liver dysfunction variables on METH pharmacokinetics.

METHODS

Sham or BDL surgery was performed on male and female rats on day 0. Serum biomarker and pharmacokinetics studies with 3 mg/kg subcutaneous (SC) METH were performed on day 7. METH-induced weight loss was measured on day 8. Liver histology evaluation and brain METH concentration measurements were performed on day 9.

RESULTS

While BDL surgery produced significantly elevated alanine aminotransferase and bile duct proliferation in male compared to female rats, there were no significant interactions between sex and liver function in the pharmacokinetic parameters. Both liver dysfunction and female sex, however, were associated with significantly slower METH serum clearance and significantly higher brain METH concentrations (p < .05).

CONCLUSIONS

BDL-induced hepatic dysfunction produces substantial reductions in METH clearance and increased brain METH concentrations in both male and female rats, despite less liver injury in females. This preclinical model may be useful to identify and correct potential liver dysfunction comorbidity-related problems with future pharmacotherapy for stimulant use disorder with METH prior to expensive clinical trials.

Caffeine preserves quiet sleep in preterm neonates

Caffeine is widely used in preterm neonates suffering from apnea of prematurity (AOP), and it has become one of the most frequently prescribed medications in neonatal intensive care units. Goal of this study is to investigate how caffeine citrate treatment affects sleep-wake behavior in preterm neonates. The observational study consists of 64 preterm neonates during their first 5 days of life with gestational age (GA) <32 weeks or very low birthweight of < 1500 g. A total of 52 patients treated with caffeine citrate and 12 patients without caffeine citrate were included. Sleep-wake behavior was scored in three stages: active sleep, quiet sleep, and wakefulness. Individual caffeine concentration of every neonate was simulated with a pharmacokinetic model. In neonates with GA ≥ 28 weeks, wakefulness increased and active sleep decreased with increasing caffeine concentrations, whereas quiet sleep remained unchanged. In neonates with GA < 28 weeks, no clear caffeine effects on sleep-wake behavior could be demonstrated. Caffeine increases fraction of wakefulness, alertness, and most probably also arousability at cost of active but not quiet sleep in preterm neonates. As such, caffeine should therefore not affect time for physical and cerebral regeneration during sleep in preterm neonates.

Dose-Related Concentrations of Neuroactive/Psychoactive Drugs Expected in Blood of Children and Adolescents

PURPOSE

Therapeutic drug monitoring is highly recommended for children and adolescents treated with neurotropic/psychotropic drugs. For interpretation of therapeutic drug monitoring results, drug concentrations (C/D) expected in a "normal" population are helpful to identify pharmacokinetic abnormalities or nonadherence. Using dose-related concentration (DRC) factors obtained from pharmacokinetic data, C/D ranges expected under steady state can be easily calculated by multiplication of DRC by the daily dose. DRC factors, however, are defined only for adults so far. Therefore, it was the aim of this study to estimate DRC factors for children and adolescents and compare them with those of adults.

METHODS

To obtain pharmacokinetic data (apparent total clearance of drugs from plasma after oral administration, elimination half-life, area under the curve, and minimum serum drug concentration) from children and adolescents treated with psychotropic drugs, a systematic review of published literature was performed, and the pharmaceutical companies that market these drugs were contacted. Available information was used for the calculation of DRC factors.

RESULTS

Fourteen of 26 drugs had similar DRC factors to those reported for adults; 8 and 4 had higher and lower factors, respectively. The antidepressants citalopram, clomipramine, fluvoxamine, and imipramine and the antipsychotics haloperidol and olanzapine showed higher DRC factors than those calculated for adults. The DRC factors of amphetamine and methylphenidate were higher in children (6-12 years) but not in adolescents (13-17 years). On the contrary, the antipsychotic quetiapine and the mood-stabilizing antiepileptics lamotrigine, oxcarbazepine, and topiramate showed lower DRC factors than those calculated for adults.

CONCLUSIONS

It was concluded that concentrations of neuroactive/psychoactive drugs to be expected in blood for a given dose may differ between adults and children or adolescents, most probably owing to age-dependent differences in the elimination of these drugs.

Long-term Effects of Multimodal Treatment on Adult Attention-Deficit/Hyperactivity Disorder Symptoms: Follow-up Analysis of the COMPAS Trial

IMPORTANCE

Knowledge about the long-term effects of multimodal treatment in adult attention-deficit/hyperactivity disorder (ADHD) is much needed.

OBJECTIVE

To evaluate the long-term efficacy of multimodal treatment for adult ADHD.

DESIGN, SETTING, AND PARTICIPANTS

This observer-masked, 1.5-year follow-up of the Comparison of Methylphenidate and Psychotherapy in Adult ADHD Study (COMPAS), a prospective, multicenter randomized clinical trial, compared cognitive behavioral group psychotherapy (GPT) with individual clinical management (CM) and methylphenidate (MPH) with placebo (2 × 2 factorial design). Recruitment started January 2007 and ended August 2010, and treatments were finalized in August 2011 with follow-up through March 2013. Overall, 433 adults with ADHD participated in the trial, and 256 (59.1%) participated in the follow-up assessment. Analysis began in November 2013 and was completed in February 2018.

INTERVENTIONS

After 1-year treatment with GPT or CM and MPH or placebo, no further treatment restrictions were imposed.

MAIN OUTCOMES AND MEASURES

The primary outcome was change in the observer-masked ADHD Index of Conners Adult ADHD Rating Scale score from baseline to follow-up. Secondary outcomes included further ADHD rating scale scores, observer-masked ratings of the Clinical Global Impression scale, and self-ratings of depression on the Beck Depression Inventory.

RESULTS

At follow-up, 256 of 433 randomized patients (baseline measured in 419 individuals) participated. Of the 256 patients participating in follow-up, the observer-masked ADHD Index of Conners Adult ADHD Rating Scale score was assessed for 251; the mean (SD) baseline age was 36.3 (10.1) years; 125 patients (49.8%) were men; and the sample was well-balanced with respect to prior randomization (GPT and MPH: 64 of 107; GPT and placebo: 67 of 109; CM and MPH: 70 of 110; and CM and placebo: 55 of 107). At baseline, the all-group mean ADHD Index of Conners Adult ADHD Rating Scale score was 20.6, which improved to adjusted means of 14.2 for the GPT arm and 14.7 for the CM arm at follow-up with no significant difference between groups (difference, -0.5; 95% CI, -1.9 to 0.9; P = .48). The adjusted mean decreased to 13.8 for the MPH arm and 15.2 for the placebo arm (difference, -1.4; 95% CI, -2.8 to -0.1; P = .04). As in the core study, MPH was associated with a larger reduction in symptoms than placebo at follow-up. These results remained unchanged when accounting for MPH intake at follow-up. Compared with participants in the CM arm, patients who participated in group psychotherapy were associated with less severe symptoms as measured by the self-reported ADHD Symptoms Total Score according to the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) of Conners Adult ADHD Rating Scale (AMD, -2.1; 95% CI, -4.2 to -0.1; P = .04) and in the subscale of reducing pure hyperactive symptoms, measured via the Diagnostic Checklist for the diagnosis of ADHD in adults (AMD, -1.3; 95% CI, -2.8 to 0.1; P = .08). Regarding the Clinical Global Impression scale assessment of effectiveness, the difference between GPT and CM remained significant at follow-up (odds ratio, 1.63; 95% CI, 1.03-2.59; P = .04). No differences were found for any comparison concerning depression as measured with the Beck Depression Inventory.

CONCLUSIONS AND RELEVANCE

Results from COMPAS demonstrate a maintained improvement in ADHD symptoms for adults 1.5 years after the end of a 52-week controlled multimodal treatment period. The results indicate that MPH treatment combined with GPT or CM provides a benefit lasting 1.5 years. Confirming the results of the core study, GPT was not associated with better results regarding the primary outcome compared with CM.

TRIAL REGISTRATION

isrctn.org Identifier: ISRCTN54096201.

Stimulant Use in Pregnancy: An Under-recognized Epidemic Among Pregnant Women

Stimulant use, including cocaine, methamphetamines, ecstasy, and prescription stimulants, in pregnancy is increasingly common. In the United States, stimulants are the second most widely used and abused substances during pregnancy and pregnant women using stimulants in pregnancy are at increased risk of adverse perinatal, neonatal, and childhood outcomes. In this review, we describe the pharmacology, pathophysiology, and epidemiology of stimulants, summarize the maternal and neonatal effects of perinatal stimulant use, and outline treatment options for stimulant use disorders among pregnant women. Development of effective treatment strategies for stimulant use disorders identified among pregnant women are urgently needed.

Lisdexamfetamine Dimesylate: A Review in Paediatric ADHD

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

Effects of Caffeine Supplementation on Performance in Ball Games

Although a large body of evidence exists documenting the ergogenic properties of caffeine, most studies have focused on endurance performance. However, findings from endurance sports cannot be generalized to performance in ball games where, apart from having a high level of endurance, successful athletic performances require a combination of physiological, technical and cognitive capabilities. The purpose of this review was to critically evaluate studies that have examined the effect of a single dose of caffeine in isolation on one or more of the following performance measures: total distance, sprint performance, agility, vertical jump performance and accuracy in ball games. Searches of three major databases resulted in 19 studies (invasion games: 13; net-barrier games: 6) that evaluated the acute effects of caffeine on human participants, provided the caffeine dose administered, and included a ball games specific task or simulated match. Improvements in sprint performance were observed in 8 of 10 studies (80%), and vertical jump in 7 of 8 studies (88%). Equivocal results were reported for distance covered, agility and accuracy. Minor side effects were reported in 4 of 19 studies reviewed. Pre-exercise caffeine ingestion between 3.0 and 6.0 mg/kg of body mass appears to be a safe ergogenic aid for athletes in ball games. However, the efficacy of caffeine varies depending on various factors, including, but not limited to, the nature of the game, physical status and caffeine habituation. More research is warranted to clarify the effects of caffeine on performance measures unique to ball games, such as agility and accuracy. It is essential that athletes, coaches and practitioners evaluate the risk-benefit ratio of caffeine ingestion strategies on an individual case-by-case basis.

Controlling for caffeine in cardiovascular research: A critical review

Caffeine, the most widely consumed drug in the world, exerts numerous effects on cardiovascular activity. Thus, it is important and advisable to control for caffeine consumption in studies examining caffeine and/or cardiovascular activity and reactivity. This paper 1) reviews the literature concerning caffeine's effects on cardiovascular parameters; 2) summarizes the widely varying protocols used to control for the drug in extant cardiovascular literature, and 3) provide guidelines for caffeine control procedures to minimize potentially confounding acute and withdrawal effects of the drug. An abstention period equal to the average half-life of the drug is recommended for creation of methodological controls for caffeine. Additional methodological recommendations are described concerning factors that moderate the half-life of caffeine. When feasible, researchers should consider and aim to control for caffeine's acute and extended psychophysiological effects. This understudied issue has fundamental implications for caffeine-related investigations and research in psychophysiology and behavioral medicine.

[Side effects of methylphenidate in children and the young]

INTRODUCTION

The use of psychostimulants has been present in common medical practice since the 20th century and has undergone an exponential growth in terms of the number of prescriptions.

AIM

To review the current state of knowledge about the side effects of psychostimulants in the child and teen populations.

DEVELOPMENT

A review was performed by searching in different databases and included clinical analyses, observational prospective studies and systematic reviews. A minimum increase in blood pressure and heart rate are observed, but some studies highlight an underestimation of the long-term risk. As regards appetite and growth, almost all the current literature points to a slowing of the rate of growth, which is regained on interrupting treatment. One important factor, as is the parallel evolution of bone age, has not been evaluated in most of the studies carried out to date. No significant worsening of sleep was noted in patients treated with psychostimulants with respect to those who are not being treated. With regard to the central nervous system, there does not seem to be any evidence of an increased risk of the appearance or exacerbation of tics following introduction of the treatment. Affect and emotion are areas that have been barely explored.

CONCLUSIONS

It is important to have more evidence on the safety of these drugs. It is therefore essential to have access to studies that cover a period of time consistent with the duration of these treatments.

New Formulations of Methylphenidate for the Treatment of Attention-Deficit/Hyperactivity Disorder: Pharmacokinetics, Efficacy, and Tolerability

Psychostimulants are the recommended first-line pharmacological treatment for attention-deficit/hyperactivity disorder (ADHD). Methylphenidate is one of the most commonly used psychostimulants worldwide. Given that immediate-release and/or tablet/capsule formulations may decrease adherence to methylphenidate treatment, several drug companies have been developing novel long-acting and/or liquid/chewable formulations that may improve adherence as well as (for long-acting formulations) reduce abuse potential, decrease stigma associated with multiple administrations per day, and decrease the potential for adverse effects related to dosage peak. Here, we review the pharmacokinetics, efficacy, and tolerability of novel formulations of methylphenidate that are in development or have been approved by the US FDA or European Medicines Agency (EMA) in the last 5 years. We searched the websites of the FDA, EMA, ClinicalTrials.gov, and the pertinent drug companies. We also searched PubMed, Ovid databases (MEDLINE, PsycINFO, Embase + Embase classic), and ISI Web of Knowledge (Web of Science [Science Citation Index Expanded], Biological Abstracts, Biosis, Food Science and Technology Abstracts) to retrieve any additional pertinent information. We found data from trials for the following compounds: (1) methylphenidate extended-release oral suspension (MEROS; NWP06, Quillivant™); (2) methylphenidate extended-release chewable capsules (NWP09, QuilliChew ER™); (3) methylphenidate hydrochloride extended-release capsules (Aptensio XR™); (4) methylphenidate extended-release orally disintegrating tablets (XR-ODT; NT-0102, Cotempla™); (5) ORADUR technology (once-daily tamper-resistant formulation) methylphenidate sustained release (SR); and (6) methylphenidate modified-release (HLD-200; Bejorna™). Overall, available evidence based on trials suggests these compounds have good efficacy and tolerability. Future research should further explore the effectiveness and tolerability of these new formulations as well as their potential to improve adherence to treatment in the 'real world' via pragmatic trials.

Metabolism and pharmacokinetics of morphine in neonates: A review

Morphine is an agonist of the µ and k receptors, whose activation results in analgesia. Morphine-like agonists act through the µ opioid receptors to cause pain relief, sedation, euphoria and respiratory depression. Morphine is glucuronidated and sulfated at positions 3 and 6; the plasma concentration ratios correlate positively with birth weight, which probably reflects increased liver weight with increasing birth weight. Moreover, morphine clearance correlates positively with gestational age and birth weight. Steady-state morphine plasma concentrations are achieved after 24-48 hours of infusion, but the glucuronide metabolite plasma concentrations do not reach steady state before 60 hours. The morphine-3-glucuronide metabolite has lower clearance, a shorter half-life and a smaller distribution volume compared with the morphine-6 metabolite, which is the most active morphine-like agonist. Ordinary doses cause constipation, urinary retention and respiratory depression. Neonatal pain relief may require a blood level of approximately 120 ng/ml, whereas lower levels (20-40 ng/ml) seem adequate for children. A bibliographic search was performed using the PubMed database and the keywords "morphine metabolism neonate" and "morphine pharmacokinetics neonate". The initial and final cutoff points were January 1990 and September 2015, respectively. The results indicate that morphine is extensively glucuronidated and sulfated at positions 3 and 6, and that the glucuronidation rate is lower in younger neonates compared with older infants. Although much is known about morphine in neonates, further research will be required to ensure that recommended therapeutic doses for analgesia in neonates are evidence based.

A Comparison of Effectiveness of Parent Behavioral Management Training and Methylphenidate on Reduction of Symptomsof Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is one of the most common psychological disorders of childhood. Methylphenidate is highly effective in the treatment of ADHD. This study aimed to determine the effectiveness of combined Parent behavioral management training (PBMT) and medication treatment (Methylphenidate) in reducing ADHD symptoms in 6-12-year-old children, using randomized sampling. A total of 50 children with ADHD were assigned into two groups: an experimental group of PBMT and a control group of medication treatment (Methylphenidate) without other interventions. Conners' Parent Rating Scale (CPRS-48) was employed before and after interventions to determine the effects. Descriptive Statistics method (consisting of Mean and Standard deviation) and Statistical inference method, (including t-test and Levene's Test) were used for data analysis.  Findings revealed that the combined behavioral intervention of PBMT and methylphenidate treatment is more effective in reduction of ADHD in children. The difference of means between pre-test and post-test of CPRS in the experimental group was equal to 10.77, and it was equal to 1.88 in the control group. In addition, PBMT was more effective in the case of younger parents (P<0.025). However, parents' education level did not affect the behavioral intervention (P<0.025).The findings suggest that combined intervention of PBMT and methylphenidate is effective in reducing the symptoms of ADHD in children.

Characterization of Atomoxetine Biotransformation and Implications for Development of PBPK Models for Dose Individualization in Children

Atomoxetine (ATX) is a second-line nonstimulant medication used to control symptoms of attention deficit hyperactivity disorder (ADHD). Inconsistent therapeutic efficacy has been reported with ATX, which may be related to variable CYP2D6-mediated drug clearance. We characterized ATX metabolism in a panel of human liver samples as a basis for a bottom-up PBPK model to aid in ATX exposure prediction and control. Km, Vmax, and Clint values in pooled human liver microsomes (HLMs) were 2.4 µM, 479 pmol/min/mg protein, and 202 µl/min/mg protein, respectively. Mean population values of kinetic parameters are not adequate to describe variability in a population, given that Km, Vmax, and Clint values from single-donor HLMs ranged from 0.93 to 79.2 µM, 20.0 to 1600 pmol/min/mg protein, and 0.3 to 936 µl/min/mg protein. All kinetic parameters were calculated from 4-hydroxyatomoxetine (4-OH-ATX) formation. CYP2E1 and CYP3A contributed to 4-OH-ATX formation in livers with CYP2D6 intermediate and poor metabolizer status. In HLMs with lower CYP2D6 activity levels, 2-hydroxymethylatomoxetine (2-CH2OH-ATX) formation became a more predominant pathway of metabolism, which appeared to be catalyzed by CYP2B6. ATX biotransformation at clinically relevant plasma concentrations was characterized in a panel of pediatric HLM (n = 116) samples by evaluating primary metabolites. Competing pathways of ATX metabolism [N-desmethylatomoxetine (NDM-ATX) and 2-CH2OH-ATX formation] had increasing importance in livers with lesser CYP2D6 activity, but, overall ATX clearance was still compromised. Modeling ATX exposure to individualize therapy would require comprehensive knowledge of factors that affect CYP2D6 activity as well as an understanding of competing pathways, particularly for individuals with lower CYP2D6 activity.

Synergistic Skin Penetration Enhancer and Nanoemulsion Formulations Promote the Human Epidermal Permeation of Caffeine and Naproxen

We examined the extent of skin permeation enhancement of the hydrophilic drug caffeine and lipophilic drug naproxen applied in nanoemulsions incorporating skin penetration enhancers. Infinite doses of fully characterized oil-in-water nanoemulsions containing the skin penetration enhancers oleic acid or eucalyptol as oil phases and caffeine (3%) or naproxen (2%) were applied to human epidermal membranes in Franz diffusion cells, along with aqueous control solutions. Caffeine and naproxen fluxes were determined over 8 h. Solute solubility in the formulations and in the stratum corneum (SC), as well as the uptake of product components into the SC were measured. The nanoemulsions significantly enhanced the skin penetration of caffeine and naproxen, compared to aqueous control solutions. Caffeine maximum flux enhancement was associated with a synergistic increase in both caffeine SC solubility and skin diffusivity, whereas a formulation-increased solubility in the SC was the dominant determinant for increased naproxen fluxes. Enhancements in SC solubility were related to the uptake of the formulation excipients containing the active compounds into the SC. Enhanced skin penetration in these systems is largely driven by uptake of formulation excipients containing the active compounds into the SC with impacts on SC solubility and diffusivity.

Metabolomics of cocaine: implications in toxicity

Cocaine is the most commonly used illicit drug among those seeking care in Emergency Departments or drug detoxification centers. Cocaine, chemically known as benzoylmethylecgonine, is a naturally occurring substance found in the leaves of the Erythroxylum coca plant. The pharmacokinetics of cocaine is dependent on multiple factors, such as physical/chemical form, route of administration, genetics and concurrent consumption of alcohol. This review aims to discuss metabolomics of cocaine, namely by presenting all known metabolites of cocaine and their roles in the cocaine-mediated toxic effects.

Probabilistic Markov Model Estimating Cost Effectiveness of Methylphenidate Osmotic-Release Oral System Versus Immediate-Release Methylphenidate in Children and Adolescents: Which Information is Needed?

BACKGROUND

Incidence of attention deficit hyperactivity disorder (ADHD) in children and adolescents has been increasing. The disorder results in high societal costs. Policymakers increasingly use health economic evaluations to inform decisions on competing treatments of ADHD. Yet, health economic evaluations of first-choice medication of ADHD in children and adolescents are scarce and generally do not include broader societal effects.

OBJECTIVES

This study presents a probabilistic model and analysis of methylphenidate osmotic-release oral system (OROS) versus methylphenidate immediate-release (IR). We investigate and include relevant societal aspects in the analysis so as to provide cost-effectiveness estimates based on a broad societal perspective.

METHODS

We enhanced an existing Markov model and determined the cost effectiveness of OROS versus IR for children and adolescents responding suboptimally to treatment with IR. Enhancements included screening of a broad literature base, updated utility values, inclusion of costs and effects on caregivers and a change of the model type from deterministic to probabilistic.

RESULTS

The base case scenario resulted in lower incremental costs (€-5815) of OROS compared with IR and higher incremental quality-adjusted life-year (QALY) gains (0.22). Scenario analyses were performed to determine sensitivity to changes in transition rates, utility of caregivers, medical costs of caregivers and daily medication dose.

CONCLUSIONS

The results indicate that, for children responding suboptimally to treatment with IR, the beneficial effect of OROS on compliance may be worth the additional costs of medication. The presented model adds to the health economic information available for policymakers and to considerations on a broader perspective in cost-effectiveness analyses.

Population pharmacokinetics of doxapram in low-birth-weight Japanese infants with apnea

This study aimed to determine the population pharmacokinetics of doxapram in low-birth-weight (LBW) infants. A total of 92 serum concentration measurements that were obtained from 34 Japanese neonates were analyzed using nonlinear mixed-effect modeling (NONMEM). Estimates generated by NONMEM indicated that clearance of doxapram (CL; L/kg/h) was affected by postmenstrual age (PMA; weeks), body weight (BW; g), and aspartate aminotransferase (AST; IU/L). In addition, the volume of distribution (Vd; L/kg) was affected by gestational age (GA; weeks). The final pharmacokinetic model was as follows: CL = BW / PMA × 0.0453 × serum AST(-0.373); Vd = 2.54 (if GA >28 weeks) and Vd = 2.54 × 2.11 (if GA ≤28 weeks). The interindividual variabilities in CL and Vd were 39.9 and 83.0 %, respectively, and the residual variability was 20.9 %. To clarify the reasons for large interindividual variations, the enzymes involved in the metabolic pathway of doxapram were also determined. We found that doxapram was metabolized by CYP3A4/5.

CONCLUSION

We report the population pharmacokinetics of doxapram in neonates and the involvement of CYP3A4/5 in its metabolism. The final model of population pharmacokinetics may be useful for formulating a safe and effective dosage regimen and for predicting serum doxapram concentrations in neonates.

[Amphetamine abuse and drug interactions]

Party drug consumption is a growing problem in Denmark. Often these drugs are taken in combination. In this article we review the pharmacodynamic and pharmacokinetic interactions between amphetamine, other illicit drugs and prescription medicine.

Prenatal exposure to methylphenidate affects the dopamine system and the reactivity to natural reward in adulthood in rats

BACKGROUND

Methylphenidate (MPH) is a commonly-used medication for the treatment of children with Attention-Deficit/Hyperactivity Disorders (ADHD). However, its prescription to adults with ADHD and narcolepsy raises the question of how the brain is impacted by MPH exposure during pregnancy. The goal of this study was to elucidate the long-term neurobiological consequences of prenatal exposure to MPH using a rat model.

METHODS

We focused on the effects of such treatment on the adult dopamine (DA) system and on the reactivity of animals to natural rewards.

RESULTS

This study shows that adult male rats prenatally exposed to MPH display elevated expression of presynaptic DA markers in the DA cell bodies and the striatum. Our results also suggest that MPH-treated animals could exhibit increased tonic DA activity in the mesolimbic pathway, altered signal-to-noise ratio after a pharmacological stimulation, and decreased reactivity to the locomotor effects of cocaine. Finally, we demonstrated that MPH rats display a decreased preference and motivation for sucrose.

CONCLUSIONS

This is the first preclinical study reporting long-lasting neurobiological alterations of DA networks as well as alterations in motivational behaviors for natural rewards after a prenatal exposure to MPH. These results raise concerns about the possible neurobiological consequences of MPH treatment during pregnancy.

Development of a physiologically based model to describe the pharmacokinetics of methylphenidate in juvenile and adult humans and nonhuman primates

The widespread usage of methylphenidate (MPH) in the pediatric population has received considerable attention due to its potential effect on child development. For the first time a physiologically based pharmacokinetic (PBPK) model has been developed in juvenile and adult humans and nonhuman primates to quantitatively evaluate species- and age-dependent enantiomer specific pharmacokinetics of MPH and its primary metabolite ritalinic acid. The PBPK model was first calibrated in adult humans using in vitro enzyme kinetic data of MPH enantiomers, together with plasma and urine pharmacokinetic data with MPH in adult humans. Metabolism of MPH in the small intestine was assumed to account for the low oral bioavailability of MPH. Due to lack of information, model development for children and juvenile and adult nonhuman primates primarily relied on intra- and interspecies extrapolation using allometric scaling. The juvenile monkeys appear to metabolize MPH more rapidly than adult monkeys and humans, both adults and children. Model prediction performance is comparable between juvenile monkeys and children, with average root mean squared error values of 4.1 and 2.1, providing scientific basis for interspecies extrapolation of toxicity findings. Model estimated human equivalent doses in children that achieve similar internal dose metrics to those associated with pubertal delays in juvenile monkeys were found to be close to the therapeutic doses of MPH used in pediatric patients. This computational analysis suggests that continued pharmacovigilance assessment is prudent for the safe use of MPH.

Stereoselective anticonvulsant and pharmacokinetic analysis of valnoctamide, a CNS-active derivative of valproic acid with low teratogenic potential

OBJECTIVE

Valnoctamide (VCD), a central nervous system (CNS)-active chiral constitutional isomer of valpromide, the corresponding amide of valproic acid (VPA), is currently undergoing phase IIb clinical trials in acute mania. VCD exhibits stereoselective pharmacokinetics (PK) in animals and humans. The current study comparatively evaluated the pharmacodynamics (PD; anticonvulsant activity and teratogenicity) and PK of the four individual stereoisomers of VCD.

METHODS

The anticonvulsant activity of VCD individual stereoisomers was evaluated in several rodent anticonvulsant models including maximal electroshock, 6 Hz psychomotor, subcutaneous metrazol, and the pilocarpine-induced and soman-induced status epilepticus (SE). The PK-PD (anticonvulsant activity) relationship of VCD stereoisomers was evaluated following intraperitoneal administration (70 mg/kg) to rats. Induction of neural tube defects (NTDs) by VCD stereoisomers was evaluated in a mouse strain that was highly susceptible to teratogen-induced NTDs.

RESULTS

VCD had a stereoselective PK, with (2S,3S)-VCD exhibiting the lowest clearance, and consequently a twice-higher plasma exposure than all other stereoisomers. Nervertheless, there was less stereoselectivity in VCD anticonvulsant activity and each stereoisomer had similar median effective dose (ED)50 values in most models. VCD stereoisomers (258 or 389 mg/kg) did not cause NTDs. These doses are 3-12 times higher than VCD anticonvulsant ED50 values.

SIGNIFICANCE

VCD displayed stereoselective PK that did not lead to significant stereoselective activity in various anticonvulsant rodent models. If VCD exerted its broad-spectrum anticonvulsant activity using a single mechanism of action (MOA), it is likely that it would exhibit a stereoselective PD. The fact that there was no significant difference between racemic VCD and its individual stereoisomers suggests that VCD's anticonvulsant activity is due to multiple MOAs.

[LC-MS/MS assay of methylphenidate: stability and pharmacokinetics in human]

The study aims to solve the instability problem of methylphenidate (MPH) in plasma, and establish a LC-MS/MS method for simultaneous determining of MPH in human plasma. The stabilities of MPH in different media were studied, and the degradation characteristics of MPH in these media were also investigated by HPLC and LC-MS/MS. To a 200 microL aliquot of freshly collected plasma sample, 10 microL 2% formic acid was added immediately to prevent the hydrolysis of MPH in human plasma samples. Chromatographic separation was performed on a Sapphire C18 column using the mobile phase of methanol - 5 mmol.L-1 ammonium acetate buffer solution containing 0.1% formic acid (46 : 54). MPH was quantified by tandem mass spectrometry operating in positive electrospray ionization mode with multiple reaction monitoring. The detection used the transitions of protonated molecules at m/z 234.2-->84.1 for MPH and m/z 260.3-->183.1 for propranolol (IS), separately. The intra- and inter-assay precisions were all below 5.0%. The accuracies were all in standard ranges. The linear calibration curve was obtained in the concentration range of 0.035-40 ng.mL-1. The methods fulfilled the demand. The method was used to determine the concentration of MPH in human plasma after a single dose of 36 mg MPH tablet to 6 healthy Chinese volunteers. The method is suitable for the precisely determination of MPH and for pharmacokinetic study of MPH in human plasma.

[Triage DOA screening in a case of methamphetamine and its analogue poisoning]

CASE REPORT

A 20-year-old woman presented with the chest pain, nausea, respiratory strange feeling, and a large quantity of sweating. On the stimulant zone of 8 groups of drugs of Triage DOA screening it showed an equivocal positivity while all of the other zones gave negative results. She denied taking drugs. No injection scar was found. And she was then hospitalized because little was known about her symptoms. When the unconscious patient was discovered at rest room inside hospital the next day, she was transferred to emergency and critical care center. In the same screening test positivity on the stimulant zone was observed, and furthermore both amphetamine and methamphetamine were detected by GCMS analysis. For 4 days positivity on the stimulant zone lasted. From the fact of disturbance of consciousness, restlessness, excitation and tachycardia, respiration disorder, and the pupil dilatation drug poisoning was deeply suspected.

DISCUSSION

While the stimulant zone of Triage DOA showed the equivocal positivity when 7 hours has elapsed until she became aware of abnormality and hospitalized, in the same screening of 30 hours later positivity was verified clearly. Several problems derived from the detection method, pharmacokinetic factors and pharmacodynamic aspect were discussed as for the difference of the results detected.

Single doses of THC and cocaine decrease proficiency of impulse control in heavy cannabis users

BACKGROUND AND PURPOSE

Cannabis is the most popular drug used in the European Union, closely followed by cocaine. Whereas cannabis impairs neurocognitive function in occasional cannabis users, such impairments appear less prominent in heavy users, possibly as a result of tolerance. The present study was designed to assess whether the impairing effects of Δ(9) -tetrahydrocannabinol (THC) in heavy cannabis users would present in a wide range of neuropsychological functions or selectively affect specific performance domains. We also assessed the acute effects of cocaine on neurocognitive functions of heavy cannabis users.

EXPERIMENTAL APPROACH

Heavy cannabis users, who had a history of cocaine use (n = 61), participated in a double-blind, placebo-controlled, three-way crossover study. Subjects received single doses of cocaine HCl (300 mg), cannabis (THC μg·kg(-1) ) and placebo, and completed a number of tests measuring impulse control and psychomotor function.

KEY RESULTS

Single doses of cannabis impaired psychomotor function and increased response errors during impulsivity tasks. Single doses of cocaine improved psychomotor function and decreased response time in impulsivity tasks, but increased errors.

CONCLUSIONS AND IMPLICATIONS

Heavy cannabis users display impairments in a broad range of neuropsychological domains during THC intoxication. Impairments observed in psychomotor tasks, but not in impulsivity tasks, appeared smaller in magnitude as compared with those previously reported in occasional cannabis users. Heavy cannabis users were sensitive to the stimulating and inhibitory effects of cocaine on psychomotor function and impulsivity respectively. The reduction in proficiency in impulse control may put drug users at increased risk of repeated drug use and addiction.

Clinical and pharmacological aspects of bath salt use: a review of the literature and case reports

Bath salts are designer drugs with stimulant properties that are a growing medical and psychiatric concern due to their widespread availability and use. Although the chemical compounds in the mixtures referred to as "bath salts" vary, many are derivatives of cathinone, a monoamine alkaloid. Cathinones have an affinity for dopamine, serotonin, and norepinephrine synapses in the brain. Because of the strong selection for these neurotransmitters, these drugs induce stimulating effects similar to those of methamphetamines, cocaine, and 3,4-methylenedioxy-N-methylamphetamine (MDMA). Much of the emerging information about bath salts is from emergency department evaluation and treatment of severe medical and neuropsychiatric adverse outcomes. This review consists of a compilation of case reports and describes the emergent literature that illustrates the chemical composition of bath salts, patterns of use, administration methods, medical and neuropsychiatric effects, and treatments of patients with bath salt toxicity.

2C or not 2C: phenethylamine designer drug review

New groups of synthetic "designer drugs" have increased in popularity over the past several years. These products mimic the euphoric effects of other well-known illicit drugs but are advertised as "legal" highs and are sold over the internet, at raves and night clubs, and in head shops. The 2C series drugs are ring-substituted phenethylamines that belong to a group of designer agents similar in structure to 3,4-methylenedioxy-N-methylamphetamine (MDMA, Ecstasy). Understanding the pharmacology and toxicology of these agents is essential in order to provide the best medical care for these patients. This review focuses on the pharmacology, pharmacokinetics, clinical effects, and treatment of 2C drug intoxication based on available published literature. Multiple names under which 2C drugs are sold were identified and tabulated. Common features identified in patients intoxicated with 2Cs included hallucinations, agitation, aggression, violence, dysphoria, hypertension, tachycardia, seizures, and hyperthermia. Patients may exhibit sympathomimetic symptoms or symptoms consistent with serotonin toxicity, but an excited delirium presentation seems to be consistent amongst deaths attributed to 2C drugs; at least five deaths have been reported in the literature in patients intoxicated with 2C drugs. 2C drugs are a group of designer intoxicants, many of which are marketed as legal, but may carry risks that consumers are unaware of. These drugs may be characterized by either serotonergic toxicity or a sympathomimetic toxidrome, but a presentation consistent with excited delirium is consistent amongst the reported 2C-related deaths. Treatment of 2C intoxication is primarily supportive, but immediate action is required in the context of excited delirium, hyperthermia, and seizure activity.

A methamphetamine vaccine attenuates methamphetamine-induced disruptions in thermoregulation and activity in rats

BACKGROUND

There are no approved pharmacotherapies for d-methamphetamine (METH) addiction and existing therapies have limited efficacy. Advances in using immunotherapeutic approaches for cocaine and nicotine addiction have stimulated interest in creating a similar approach for METH addiction. This study investigated whether active vaccination against METH could potentially attenuate responses to METH in vivo.

METHODS

Male Sprague Dawley rats (n = 32) received a four-boost series with one of three candidate anti-METH vaccines (MH2[R], MH6, and MH7) or a control keyhole limpet hemocyanin conjugate vaccine. Effects of METH on rectal temperature and wheel activity at 27°C ambient temperature were determined. The most efficacious vaccine, MH6, was then contrasted with keyhole limpet hemocyanin conjugate vaccine in a subsequent experiment (n = 16), wherein radiotelemetry determined home cage locomotor activity and body temperature at 23°C ambient temperature.

RESULTS

The MH6 vaccine produced high antibody titers with nanomolar affinity for METH and sequestered METH in the periphery of rats. In experiment 1, the thermoregulatory and psychomotor responses produced by METH at 27°C were blocked in the MH6 group. In experiment 2, METH-induced decreases in body temperature and locomotor activity at 23°C were also attenuated in the MH6 group. A pharmacokinetic study in experiment 2 showed that MH6-vaccinated rats had higher METH serum concentrations, yet lower brain METH concentrations, than control rats, and METH concentrations correlated with individual antibody titer.

CONCLUSIONS

These data demonstrate that active immunopharmacotherapy provides functional protection against physiological and behavioral disruptions induced by METH.

Single-Dose Pharmacokinetics of Multilayer-Release Methylphenidate and Immediate-Release Methylphenidate in Children With Attention-Deficit/Hyperactivity Disorder

The objective of this study was to compare the single-dose pharmacokinetics of multilayer-release and immediate-release methylphenidate in children with attention-deficit/hyperactivity disorder. Patients 6- to 12-years-old with a DSM-IV diagnosis of attention-deficit/hyperactivity disorder were randomized to receive multilayer-release methylphenidate (qd) or immediate-release methylphenidate (bid) at equivalent doses, with a 14-day washout between treatments. Plasma samples were collected predosing and 1, 2, 3, 4, 5, 6, 8, 10, 12, and 24 hours postdose. Pharmacokinetic analysis was conducted on 14 patients (1 female, 13 male; mean age: 9.6 +/- 2.5 years [range, 6-12]). The mean dose of methylphenidate received by these patients in both phases of the study was 38.6 mg/d (range, 20-80 mg/d). The relative AUC(0-t) and C(max 0-4) ratios for multilayer-release compared with immediate-release methylphenidate were 100.8% and 78.8%, respectively. Multilayer-release methylphenidate produces a biphasic concentration-time profile, with a rapid initial increase in plasma concentration that is maintained throughout the school day.

A Single-Dose, Two-Way Crossover, Bioequivalence Study of Dexmethylphenidate HCl with and without Food in Healthy Subjects

Attention deficit hyperactivity disorder (ADHD) in children is effectively treated by racemic oral methylphenidate (dl-MPH). The d-isomer (d-MPH) has been developed as an improved treatment for ADHD since only half the racemic dose is used. This study, performed in healthy subjects, assessed the effect of food on the pharmacokinetics of dexmethylphenidate hydrochloride (d-MPH HCl) in a single dose (2 x 10-mg tablets), two-way crossover with d-MPH administered to subjects in both a fasting state or after a high-fat breakfast. There were no serious or unexpected adverse events during the course of this study, with most events reported in comparable numbers of fed and fasted subjects. The bioequivalence of d-MPH was similar with or without food, with 90% confidence intervals of 88.2% to 104.6% and 105.9% to 118.2% for ln(C(max)) and ln[(AUC(0-infinity))], respectively. There was a marginal but statistically significant 1-hour increase in t(max) in the fed versus fasted state, reflecting an absorption delay. The rate of formation of the major metabolite, d-ritalinic acid (d-RA), was marginally decreased ( approximately 14%) after food. The extent of exposure to d-RA was similar (within 1.2%) between both treatments. There was a marginal but statistically significant difference in mean t(max) for d-RA between fed and fasted conditions, with peak concentration occurring 1.5 hours later after d-MPH administration with food. There was no measurable in vivo chiral inversion of d-MPH to l-MPH in plasma. In addition, the metabolism of d-MPH was stereospecific as d-MPH only produced d-RA. In summary, food had no substantial effect on the bioavailability of d-MPH, with an equivalent rate and extent of exposure obtained. Therefore, d-MPH can be administered without regard to food intake.

[Pharmacological update in attention deficit hyperactivity disorder: models of intervention and new drugs]

INTRODUCTION. Attention deficit hyperactivity disorder (ADHD) is the most frequent neurodevelopmental problem in childhood, with significant repercussions that continue into adulthood. This means that an appropriate therapeutic intervention is vital to improve its prognosis. AIMS. To identify the ideal pharmacological options according to the characteristics of the patient and to report on the new drugs. DEVELOPMENT. The work analyses how therapeutic interventions can be conditioned by the anatomical substrate of the brain, the biochemical bases, genetics, neurophysiological examinations, neuropsychological studies and the clinical symptoms and subtypes. A significant amount of importance is granted to neuropsychological studies, especially those dealing with the executive functions, including evaluation of attention, impulse control, and interference and cognitive flexibility. Taking into consideration the signal-to-noise characteristics can be useful when it comes to choosing the drug. CONCLUSIONS. The development of the pharmacological therapeutic options in ADHD opens up expectations concerning applicability and greater specificity in daily practice to fit the characteristics of each patient. Psychoeducation must always be included and a thorough study of each particular child is recommended. This should involve analysing the neuropsychological features of his or her brain function in order to be able to reflect on the ideal pharmacological option that allows more favourable progress.

The acute effects of 3,4-methylenedioxymethamphetamine and methamphetamine on driving: a simulator study

OBJECTIVES

Illicit drugs such as MDMA and methamphetamine are commonly abused drugs that have also been observed to be prevalent in drivers injured in road accidents. Their exact effect on driving and driving behavior has yet to be thoroughly investigated.

METHODS

Sixty-one abstinent recreational users of illicit drugs comprised the participant sample, with 33 females and 28 males, mean age 25.45 years. The three testing sessions involved oral consumption of 100 mg MDMA, 0.42 mg/kg methamphetamine, or a matching placebo. The drug administration was counter-balanced, double-blind, and medically supervised. At each session driving performance was assessed 3 h and 24 h post drug administration on a computerized driving simulator.

RESULTS

At peak concentration overall impairment scores for driving (F(2,118)=9.042, p<0.001) and signaling (F(2,118)=4.060, p=0.020) were significantly different for the daytime simulations. Performance in the MDMA condition was worse than both the methamphetamine (p=0.023) and placebo (p<0.001) conditions and the methamphetamine condition was also observed to be worse in comparison to the placebo (p=0.055). For signaling adherence, poorer signaling adherence occurred in both the methamphetamine (p=0.006) and MDMA (p=0.017) conditions in comparison to placebo in the daytime simulations.

CONCLUSIONS

The findings of this study have for the first time illustrated how both MDMA and methamphetamine effect driving performance, and provide support for legislation regarding testing for the presence of illicit drugs in impaired or injured drivers as deterrents for driving under the influence of illicit drugs.

[Methylphenidate misuse]

Methylphenidate (MPH) is mainly used for treatment of the attention-deficit hyperactivity syndrome (ADHS). Non-medical use of methylphenidate as recreational drug or performance enhancer has increased in recent years. Methylphenidate is also misused in combination with other drugs. Patients with ADHD are also at risk to misuse their prescribed methylphenidate medication. Oral and nasal abuse of methylphenidate is most common and is in general associated with minor or moderate sympathomimetic toxicity. In contrast, severe toxicity has been reported for both intravenous and intraarterial administration of crushed methylphenidate tablets.

[Pharmacokinetics--pharmacodynamics of modafinil in mice]

To guide the reasonable clinical application of modafinil (MOD), pharmacokinetics and pharmacodynamics of MOD in mice and the correlation between them were investigated. Male mice (Kunming strain) were given a single oral dose of MOD (120 mg x kg(-1)). The plasma concentration of MOD was measured by HPLC and the pharmacokinetic parameters were calculated with DAS 3.0 software. For another batch of male Kunming strain mice, their locomotor activities were recorded by an infrared ray passive sensor after a same oral dose of MOD, and the synchronization and correlation between the changes of MOD plasma concentration and the locomotor activity induced by MOD were compared and analyzed. The results showed that the plasma concentration-time curve of MOD was fitted to two-compartment open model with a first order absorption. The main pharmacokinetic parameters t1/2alpha, t1/2beta, t(max), C(max) and AUC(0-inifinity) were 0.42 h, 3.10 h, 1.00 h, 41.34 mg x L(-1) and 142.22 mg x L(-1) x h, respectively. MOD significantly increased locomotor activity and the effect lasted for about 4 h. The changes of MOD plasma concentration and the locomotor activity induced by MOD were synchronous. In conclusion, there is a significant correlation between the effect of MOD and its plasma concentration after administration of 120 mg x kg(-1) in mice.

Aeromedical decision making in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder is a problematic diagnosis in the context of aeromedical certification. Certain characteristics of the disorder such as impaired attention potentially affect the safe conduct of flying. Pharmacological treatment with stimulants also has issues surrounding short half-lives and effects on the recognition of fatigue. This article gives a broad overview of the issues involved and provides certification guidelines as adopted in the Australian Civil Aviation Safety Authority which may be helpful if adopted by other certification bodies.

Distribution and pharmacokinetics of methamphetamine in the human body: clinical implications

Background

Methamphetamine is one of the most toxic of the drugs of abuse, which may reflect its distribution and accumulation in the body. However no studies have measured methamphetamine's organ distribution in the human body.

Methods

Positron Emission Tomography (PET) was used in conjunction with [¹¹C]d-methamphetamine to measure its whole-body distribution and bioavailability as assessed by peak uptake (% Dose/cc), rate of clearance (time to reach 50% peak-clearance) and accumulation (area under the curve) in healthy participants (9 Caucasians and 10 African Americans).

Results

Methamphetamine distributed through most organs. Highest uptake (whole organ) occurred in lungs (22% Dose; weight ∼1246 g), liver (23%; weight ∼1677 g) and intermediate in brain (10%; weight ∼1600 g). Kidneys also showed high uptake (per/cc basis) (7%; weight 305 g). Methamphetamine's clearance was fastest in heart and lungs (7–16 minutes), slowest in brain, liver and stomach (>75 minutes), and intermediate in kidneys, spleen and pancreas (22–50 minutes). Lung accumulation of [¹¹C]d-methamphetamine was 30% higher for African Americans than Caucasians (p<0.05) but did not differ in other organs.

Conclusions

The high accumulation of methamphetamine, a potent stimulant drug, in most body organs is likely to contribute to the medical complications associated with methamphetamine abuse. In particular, we speculate that methamphetamine's high pulmonary uptake could render this organ vulnerable to infections (tuberculosis) and pathology (pulmonary hypertension). Our preliminary findings of a higher lung accumulation of methamphetamine in African Americans than Caucasians merits further investigation and questions whether it could contribute to the infrequent use of methamphetamine among African Americans.

A PET study examining pharmacokinetics and dopamine transporter occupancy of two long-acting formulations of methylphenidate in adults

The delivery systems of two long-acting formulations of methylphenidate (MPH) were designed for different durations. Diffucaps bead-delivery system (DBDS)-MPH was designed to last 8 h and osmotically controlled-release oral delivery system (OROS)-MPH was designed to last 12 h. While the plasma pharmacokinetics and timing of efficacy have been studied, the corresponding central nervous system dopamine transporter (DAT) occupancies are unknown. In this study, 21 healthy volunteers underwent PET imaging with 11C Altropane before and after administration of oral doses of DBDS-MPH and OROS-MPH. Each subject received 40 mg DBDS-MPH and 36 mg OROS-MPH on different days. PET imaging occurred at 10 h after dosing. Each subject was injected with 5 mCi of 11C Altropane and serial images of the brain were acquired over 60 min with a Siemens HR+ PET camera. Binding potentials (BP, k3/k4) were calculated from time-activity curves using the simplified reference region method with cerebellum as reference. Transporter occupancy was calculated by standard methods. At 10 h, plasma d-MPH levels were lower (3.8+/-1.2 vs. 5.2+/-2.0) and brain DAT occupancy was lower (34.8+/-12.9 vs. 44.3+/-11.8) for DBDS-MPH than OROS-MPH. Across the range of values, for each unit of change in plasma d-MPH level there was a larger change in DAT occupancy with the DBDS-MPH formulation than with the OROS-MPH formulation. As predicted from previous pharmacokinetic and efficacy data, the average plasma level and DAT occupancy of 36 mg OROS-MPH was >40 mg DBDS-MPH at 10 h. Moreover, a relatively small difference in plasma levels (1.4 ng/ml at 10 h) was associated with a more impressive difference in DAT occupancy ( approximately 10% at 10 h).

Pharmacokinetic considerations in the treatment of pediatric behavioral issues

TOPIC

A review of psychopharmacology and the genetic considerations with pharmokinetics is followed through a case study to demonstrate the optimal clinical treatment of the child with pediatric behavioral issues.

PURPOSE

The knowledge of the pharmacokinetic and pharmacodynamic consequences of medications in clinical practice is of the utmost importance for all pediatric nurse practitioners. Drug interactions occur when the efficacy or toxicity of a medication is changed with the addition of another medication or dosage change.

SOURCES

An integrative literature review from nursing, medicine, psychology, and child psychiatry.

CONCLUSIONS

The current climate of a child psychiatric specialist shortage leaves the charge of this vulnerable population in the hands of the primary care provider. Pediatric primary care now requires a clear understanding of the psychostimulant and non-stimulant medications, thorough screening of each child, appropriate dosage regulation, and close monitoring of all outcomes. It is imperative that pediatric nurse practitioners understand the pharmacological interactions and safety in the treatment of children with behavioral issues.

An open study of adjunct OROS-methylphenidate in children who are atomoxetine partial responders: II. Tolerability and pharmacokinetics

OBJECTIVE

The aim of this study was to evaluate the tolerability of adding OROS methylphenidate (MPH) to children who are partial responders to atomoxetine (ATMX) in the treatment of attention-deficit/hyperactivity disorder (ADHD).

METHODS

This was a two-phase, 7-week, open study in children aged 6-17 years. Phase 1 initiated ATMX for a minimum of 4 weeks. Phase 2 entered partial responders to ATMX and added OROS MPH to their regimen. Safety was assessed using blood pressure and heart rate measurements, electrocardiogram readings, AEs, laboratories, and ATMX levels.

RESULTS

Fifty subjects who were partial responders to ATMX received the combination therapy, with 41 subjects completing the entire protocol. As reported elsewhere (Wilens et al., 2009 ), OROS MPH added to partial responders of ATMX was accompanied by a 40% reduction in the ADHD rating scale score and improvements in executive functioning. However, the combination of ATMX plus OROS MPH was associated with greater rates of insomnia, irritability, and loss of appetite compared to ATMX alone. A small significant increase in diastolic blood pressure was observed during adjunctive OROS MPH, with no clinically meaningful changes in electrocardiogram (ECG) parameters during the study. ATMX levels and liver function tests did not significantly change during the combination treatment.

CONCLUSION

Adjunct OROS MPH in ATMX partial responders yielded an additive adverse effect burden in this short-term study. Further controlled research with larger samples of children is warranted.