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

Prediction of Carboxylesterase 1-mediated In Vivo Drug Interaction between Methylphenidate and Cannabinoids using Static and Physiologically Based Pharmacokinetic Models

The use of cannabis products has increased substantially. Cannabis products have been perceived and investigated as potential treatments for attention-deficit/hyperactivity disorder (ADHD). Accordingly, co-administration of cannabis products and methylphenidate (MPH), a first-line medication for ADHD, is possible. Oral MPH undergoes extensive presystemic metabolism by carboxylesterase 1 (CES1), a hepatic enzyme which can be inhibited by two prominent cannabinoids, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). This prompts further investigation into the likelihood of clinical interactions between MPH and these two cannabinoids through CES1 inhibition. In the present study, inhibition parameters were obtained from a human liver S9 system and then incorporated into static and physiologically-based pharmacokinetic (PBPK) models for prediction of potential clinical significance. The inhibition of MPH hydrolysis by THC and CBD was reversible, with estimated unbound inhibition constants (Ki,u) of 0.031 and 0.091 µM, respectively. The static model predicted a mild increase in MPH exposure by concurrent THC (34%) and CBD (94%) from smoking a cannabis cigarette and ingestion of prescriptive CBD, respectively. PBPK models suggested no significant interactions between single doses of MPH and CBD (2.5 - 10 mg/kg) when administered simultaneously, while a mild interaction (area under drug concentration-time curve increased by up to 55% and maximum concentration by up to 45%) is likely if multiple doses of CBD (10 mg/kg twice daily) are administered. In conclusion, the pharmacokinetic disposition of MPH can be potentially influenced by THC and CBD under certain clinical scenarios. Whether the magnitude of predicted interactions translates into clinically relevant outcomes requires verification in an appropriately designed clinical study. SIGNIFICANCE STATEMENT: This work demonstrated a potential mechanism of drug-drug interactions between methylphenidate (MPH) and two major cannabinoids (Δ9-tetrahydrocannabinol [THC] and cannabidiol [CBD]) not previously reported. We predicted a mild interaction between MPH and THC when the cannabinoid exposure occurred via cannabis smoking. Mild interactions between MPH and CBD were predicted with multiple oral administrations of CBD.

Absorption Differences between Immediate-Release Dexmethylphenidate and dl-Methylphenidate

The postulate that twice the milligram/kilogram dose of dl-methylphenidate (dl-MPH) would result in equal exposure to d-MPH compared with half that milligram/kilogram dose of the chiral switch product dexmethylphenidate (d-MPH) was tested. Using a randomized, crossover study design, 12 men and 12 women received either immediate-release (IR) dl-MPH (0.3 mg/kg) or IR d-MPH (0.15 mg/kg). Relative bioavailability comparisons included partial area under the plasma concentration-time curves (pAUC0-3 h) for d-MPH. The pAUC0-3 h is a new regulatory metric presently only required for bioequivalence testing of a specific dl-MPH modified-release product. The geometric mean ratios for both the Cmax and area under the plasma concentration-time curve (AUC0-∞) were within the 90% confidence interval (CI) regulatory range of 0.8-1.25, indicating that these two drugs were bioequivalent in terms of d-MPH. However, the pAUC0-3 h geometric mean ratio for d-MPH after IR dl-MPH versus IR d-MPH was 0.76 (P < 0.001; 90% CI, 0.67-0.87), showing significantly less early exposure to the d-isomer than IR d-MPH. The 1-hour d-MPH concentration after dl-MPH was 56% of that after the enantiopure drug. The maximum d-MPH plasma concentration (Cmax) for dl-MPH was also significantly lower for dl-MPH (P < 0.05; CI, 1.02-1.19), whereas the AUC0-∞ ratio of 0.89 was not significantly different (P = 0.21; CI, 0.98-1.13). The AUC0-3 h difference reported here points to the potential limitations of using bioequivalence for sound predictions of dose-response relationships. Knowledge of the greater early exposure to d-MPH after the pure d-isomer drug compared with the racemate may contribute to drug individualization/optimization in the treatment of attention deficit hyperactivity disorder.

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.

Pharmacokinetics and therapeutic effect of OROS methylphenidate under different breakfast conditions in children with attention-deficit/hyperactivity disorder

OBJECTIVE

To examine the pharmacokinetics (PKs) and pharmacodynamics (PDs) of OROS methylphenidate (OROS MPH) dosed once daily (QD) versus an early standard regimen (immediate-release [IR] MPH dosed three times daily [TID]) under various breakfast conditions.

METHODS

This single-center, double-blind, double-dummy, randomized, crossover study of OROS MPH (NCT00269815) in children aged 6 to 12 years with attention-deficit/hyperactivity disorder evaluated the PKs and PDs of MPH given with different breakfast conditions: OROS MPH administered after a high-fat breakfast, after a normal breakfast, or after fasting and IR MPH administered after a normal breakfast or after fasting in the morning and at two subsequent time points during the day. To maximize information, patients were divided into two groups, each receiving three of the five treatments for 1 day in a three-period, randomized, crossover design. Patients were assigned to 1 of 3 dosage levels (OROS MPH 18, 36, and 54 mg QD, and an assumed equivalent regimen of IR MPH 5, 10, and 15 mg given TID) based on their prestudy established clinical dose of IR MPH. PD measurements included Combined-Attention and Deportment scores on a rating scale of school behavior (the Swanson, Kotkin, Agler, M-Flynn, and Pelham), global assessments of efficacy, and activity monitor levels during academic seatwork. Serial blood samples for PK analysis were taken predose, and then every 60 to 90 minutes until 11.5 hours postdose. Vital signs were assessed predose, and then every 1.5 to 2.5 hours until 11.5 hours postdose.

RESULTS

Of the 32 patients enrolled, 31 completed the study. The PK profiles for MPH after OROS MPH administration were similar under all conditions (with normal, high-fat breakfast, or fasting). No bioequivalence tests of OROS MPH and IR MPH under various breakfast conditions were done because there were so few patients in each dose level of treatment. The two IR MPH conditions (after normal breakfast and fasting) were not compared. The drug-to-metabolite ratios (area under the curve) for all OROS MPH and IR MPH treatments were similar. OROS MPH and IR MPH provided a similar therapeutic effect, irrespective of breakfast conditions, as demonstrated by the Swanson, Kotkin, Agler, M-Flynn, and Pelham Attention and Deportment measures and global assessments. No serious adverse events, no deaths, and no clinically significant changes in vital signs were reported, except for one patient who was discontinued early because of repeated systolic blood pressure elevations on study day 1.

CONCLUSIONS

The results of this study demonstrate that in children with attention-deficit/hyperactivity disorder, administering OROS MPH with or without food produces similar PK and PD profiles.

Oral osmotically driven systems: 30 years of development and clinical use

The number of marketed oral osmotically driven systems (OODS) has doubled in the last 10 years. The main clinical benefits of OODS are their ability to improve treatment tolerability and patient compliance. These advantages are mainly driven by the capacity to deliver drugs in a sustained manner, independent of the drug chemical properties, of the patient's physiological factors or concomitant food intake. However, access to these technologies has been restricted by the crowded patent landscape and manufacturing challenges. In this review article, we intend to give an overview of the OODS development in the last 30 years, detailing the technologies, specific products and their clinical use. General guidance on technology selection is described in light of the recent advances in the field. The clinical performance of these technologies is also discussed, with a focus on food effects and the in vivo-in vitro correlation. Special attention is paid to safety given the controversial case study of Osmosin. Overall, oral osmotically driven systems appear to be a promising technology for product life-cycle strategies.

Differential pharmacokinetics and pharmacodynamics of methylphenidate enantiomers: does chirality matter?

d,l-threo-methylphenidate (MPH) is an effective first-line treatment for the symptoms associated with attention-deficit/hyperactivity disorder. threo-methylphenidate inhibits the dopamine transporter and the norepinephrine transporter, resulting in elevations of these monoamines after impulse release. Although MPH has long been administered as a racemic mixture of the 2 enantiomers, d-MPH and l-MPH, converging lines of evidence drawn from investigations using in vitro systems, animal models, and humans indicate that it is predominantly, if not exclusively, d-MPH that mediates the pharmacological/therapeutic actions of MPH. In both rodent and primate animal models, the binding of radiolabeled d-MPH to dopamine transporter was found to be selective, saturable, and reversible, whereas binding of l-MPH was diffuse and nonspecific. The behavioral effects of the enantiomers of MPH have been tested in several animal models, and results indicate these observed behavioral changes are likewise mediated by d-MPH, whereas l-MPH has little or no effect.The contribution of the l-isomer to the overall pharmacological profile of the racemate remains unclear, owing to several studies suggesting that l-MPH may not be merely an inert isomeric ballast. For example, behavioral studies conducted in rats demonstrate an attenuation of the effect of d-MPH in animals pretreated with l-MPH, suggesting that l-MPH may interfere with the action of the active enantiomer. The importance of MPH chirality to central nervous system MPH receptor targeting has culminated in human imaging studies revealing that d-MPH binds specifically to striatal structures, whereas l-MPH binding is nonspecific. Taken together, data from in vitro, animal, and human studies support the premise that the d-enantiomer of MPH mediates the neurophysiological actions of MPH and therefore likely mediates its clinical efficacy.

Methylphenidate and its isomers: their role in the treatment of attention-deficit hyperactivity disorder using a transdermal delivery system

dl-threo-Methylphenidate is a highly efficacious drug for treating attention-deficit hyperactivity disorder (ADHD) that is currently administered as immediate- or controlled-release and osmotically controlled-released formulations. The drug exists as two enantiomers, d-threo-methylphenidate and l-threo-methylphenidate, with the former having been developed as a medication to treat ADHD in its own right. dl-threo-Methylphenidate undergoes enantioselective metabolism in the liver, which results in marked differences in the plasma concentrations of its isomers, depending on the route of administration and formulation. When dl-threo-methylphenidate is orally administered, the plasma concentrations of d-threo-methylphenidate are higher than those of l-threo-methylphenidate. However, with the recently developed methylphenidate transdermal system (MTS), 'first-pass' metabolism is circumvented and, as a consequence, plasma concentrations of d-threo-methylphenidate are consistent with those produced by oral formulations, but the relative concentrations of l-threo-methylphenidate are much higher, i.e. 50-60% of those of d-threo-methylphenidate. In this article, we review the pharmacokinetics and pharmacology of dl-threo-methylphenidate and its isomers to assess the extent to which their mechanism of action as noradrenaline (norepinephrine) and dopamine reuptake inhibitors is responsible for their efficacy and commonly occurring adverse effects. The major findings are that d-threo-methylphenidate and l-threo-methylphenidate share the same pharmacological profile as the parent racemate, i.e. catecholamine-selective reuptake inhibition with higher potency against dopamine versus noradrenaline reuptake in vivo. However, d-threo-methylphenidate is approximately 10-fold more potent than the l-isomer in this regard. For these drugs, their abilities not only to ameliorate the behavioural and cognitive dysfunctions in ADHD, but also to induce the common adverse effects of reduced appetite, nausea/vomiting and stomach ache, are almost certainly due to their ability to potentiate noradrenergic and/or dopaminergic function in the central and peripheral nervous systems. The sympathomimetic actions of ADHD drugs on cardiovascular function are currently an issue of concern. Since noradrenaline reuptake inhibition is the likely mediator for the effects of dl-threo-methylphenidate on blood pressure and heart rate, the more potent d-isomer will therefore be predominantly responsible. Motor and vocal tics are the other important adverse event to be considered in the treatment of ADHD. It is now accepted that tics are a frequently occurring behavioural manifestation of ADHD itself and the evidence for or against their exacerbation by treatment with dl-threo-methylphenidate or other stimulants remains highly contradictory. Focusing on the enantiomers of dl-threo-methylphenidate, it can be concluded that d-threo-methylphenidate, which is the more potent and abundant of the two isomers, is the major contributor of both efficacy and adverse effects, irrespective of the formulation or route of administration of the racemate. Moreover, for the oral, extended-release formulations of dl-threo-methylphenidate, the d-isomer represents the only pharmacologically active moiety when these medications are used in the clinic. With the MTS, plasma concentrations of l-threo-methylphenidate are higher than are achieved using oral formulations, but even in this case, it is likely that the contribution of this enantiomer to the efficacy and adverse effects of the racemate is no greater than 5-10% of the total.

Dexmethylphenidate extended-release capsules for the treatment of attention deficit hyperactivity disorder

Dexmethylphenidate is a chirally pure d-isomer of the racemic mixture of methylphenidate. The extended-release form of this compound was developed using proprietary Spheroidal Oral Drug Absorption System technology. The product is approved for the treatment of attention deficit hyperactivity disorder in individuals as young as 6 years old. It represents the first methylphenidate product approved for use in adults. The agent's delivery system is designed to provide an initial release of medication immediately after dosing, with a second release approximately 4 h later. Blood levels first peak at approximately 1.5 h, and the second peak is noted at an average of 6.5 h post-dose. Laboratory classroom studies have demonstrated clinically and statistically meaningful efficacy throughout a 12-h day. Pharmacokinetics, safety and efficacy data are reviewed.

Dexmethylphenidate hydrochloride in the treatment of attention deficit hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) affects a large number of children. For decades, the stimulants have been the mainstay of pharmacological treatment for ADHD. Dexmethylphenidate (d-MPH), the d-isomer of the traditional racemic mixtures of d,l-threo-(R,R)-MPH, was recently introduced as another potential option in the stimulant class of medications. This paper reviews and summarizes the available research literature on d-MPH regarding pharmacodynamic, pharmacokinetic, chemical structure, receptor binding, toxicology, and clinical perspectives. d-MPH potentially may offer some advantages in the realms of absorption and duration of action compared with its racemic counterpart. The differences in pharmacokinetics and clinical implications of the immediate-release and extended-release forms of d-MPH are also compared and contrasted.

Methylphenidate blood levels and therapeutic response in children with attention-deficit hyperactivity disorder: I. Effects of different dosing regimens

BACKGROUND AND PURPOSE

Methylphenidate (MPH) is a drug of choice for treating attention-deficit/hyperactivity disorder (ADHD), although its use has been complicated by its short duration of action. The development of ideal long-acting preparations requires detailed understanding of the pharmacokinetic and pharmacodynamic consequences of complex dosing regimens. The purpose of this study was to ascertain if administration paradigms that produce stable or rising MPH levels alter the rate with which MPH is absorbed, and to determine how effectively long-acting administration paradigms compare with thrice daily administration of immediate-release MPH.

METHOD

Forty-eight boys diagnosed with ADHD (mean age 10.6 +/- 1.1 year) participated in this double-blind, parallel group study to evaluate the pharmacokinetics and efficacy and of 1 mg/kg/day MPH administered in five different paradigms and placebo. Objective measures of activity and attention (McLean Motion Attention Test; M-MAT) and plasma measures of d- and l-MPH were obtained hourly during the course of a 12-hour laboratory session.

RESULTS

The rate of absorption and elimination of d-MPH was dependent on the pattern of administration, particularly on the initial bolus concentration. This suggests that d-MPH may act on the gastrointestinal system to slow absorption of additional d-MPH. There were significant differences among regimens on time course and degree of therapeutic response. Pulsatile administration produced greater improvement than escalating levels.