Model-Based Approach for Establishing the Predicted Clinical Response of a Delayed-Release and Extended-Release Methylphenidate for the Treatment of Attention-Deficit/Hyperactivity Disorder

Are all ADHD medications created equal? Exploring the differences that enable evening dosing

With more than 30 available stimulant medications, choosing among therapeutic options for attention-deficit/hyperactivity disorder (ADHD) has become increasingly complex and patient specific. All ADHD stimulants owe their action to variants of either amphetamine or methylphenidate, yet formulation and delivery system differences create unique pharmacokinetic and clinical profiles for each medication. A benefit of the diversity within ADHD pharmacotherapy is that it facilitates tailoring treatment to meet patient needs. Historically, there has been a constant among long-acting stimulant options, regardless of formulation, which was morning dosing. The introduction of delayed-release and extended-release methylphenidate (DR/ER-MPH) is the first long-acting stimulant that patients take in the evening, with the clinical effect delayed until awakening in the morning. This paradigm shift has generated questions among clinicians and continued interest in real-world experience and data. This review used available clinical data, real-world evidence, emerging analyses, and clinical experience to evaluate the characteristics of DR/ER-MPH and its clinical utility within the greater context of ADHD medications and to provide clinicians with practical guidance on the use of DR/ER-MPH in children, adolescents, and adults with ADHD.

Is the One-Compartment Model with First Order Absorption a Useful Approximation?

PURPOSE

The one-compartment model with first order absorption (ka1C) has been extensively used to fit oral data. But when the disposition parameters of the drug are not available, the bias in the parameter estimates remains unclear. In this paper, the effect of potential misspecification of the area under the curve (AUC) and the mean absorption time (MAT) was evaluated for three relatively slowly absorbed drugs/formulations.

METHODS

Assuming a three-compartment disposition model with an input (absorption) rate described as a sum of two inverse Gaussian functions (2IG3C) as the true model, the deviations of AUC and MAT estimated with simpler models were analyzed. Simpler models, as the ka1C model (Bateman function), the one-compartment model with IG input function (IG1C) and the gamma density function were fitted to the oral data alone, and compared to the fits obtained with the 2IG3C model which also uses the 3C disposition parameters of the drug. Data from pharmacokinetic studies of trospium, propiverine and ketamine in healthy volunteers were analyzed using a population approach.

RESULTS

The Bateman function (ka1C) allowed a robust estimation of the population mean AUC, but the individual estimates were highly biased. It failed in evaluating MAT. The simple alternative models did not improve the situation.

CONCLUSIONS

The Bateman function appears to be useful for estimating the population mean value of AUC after oral administration. The results reemphasize the fact that insight into the absorption process can be only gained when also intravenous reference data are available.

Pediatric attention deficit hyperactivity disorder (ADHD): 2022 updates on pharmacological management

INTRODUCTION

Pediatric attention-deficit disorder (ADHD) impacts a significant percentage of the population world-wide. Pharmacologic treatments have been shown to be safe and effective for managing symptoms. Various medication formulations exist, and new medication agents are continually approved each year.

AREAS COVERED

This article offers an overview of ADHD, an overview of both stimulant and non-stimulant medication options as well as an overview of stimulant misuse. It explores the medication mechanisms of action and side effect profiles, as well as offering an in-depth summary of the novel agents recently approved and soon-to-be approved for use in youth. PubMed and Medline were utilized. Search terms included children, adolescents, ADHD, and medication. FDA package inserts were reviewed for all medications.

EXPERT OPINION

New formulations of medications include an evening administered, extended, and delayed-release form of methylphenidate (DR/ER MPH), a methylphenidate pro-drug (serdexmethylphenidate) and an amphetamine patch. The availability of a new SNRI (selective norepinephrine reuptake inhibitor), viloxazine extended-release (VER), and the pending approval of a triple reuptake inhibitor (centanafadine) provides welcome additions to the prescriber's toolbox.

An exploratory analysis of the performance of methylphenidate regimens based on a PKPD model of dopamine and norepinephrine transporter occupancy

Methylphenidate (MPH) is a psychostimulant which inhibits the uptake of dopamine and norepinephrine transporters, DAT and NET, and is mostly used to treat Attention Deficit/Hyperactivity Disorder. The current dose optimization is done through titration, a cumbersome approach for patients. To assess the therapeutic performance of MPH regimens, we introduce an in silico framework composed of (i) a population pharmacokinetic model of MPH, (ii) a pharmacodynamic (PD) model of DAT and NET occupancy, (iii) a therapeutic box delimited by time and DAT occupancy, and (iv) a performance score computation. DAT occupancy data was digitized (n = 152) and described with Emax models. NET occupancy was described with a KPD model. We used this integrative framework to simulate the performance of extended-release (18-99 mg) and tid MPH regimens (25-40 mg). Early blood samples of MPH seem to lead to higher DAT occupancy, consistent with an acute tolerance observed in clinical rating scales. An Emax model with a time-dependent tolerance was fitted to available data to assess the observed clockwise hysteresis. Peak performance is observed at 63 mg. While our analysis does not deny the existence of an acute tolerance, data precision in terms of formulation and sampling times does not allow a definite confirmation of this phenomenon. This work justifies the need for a more systematic collection of DAT and NET occupancy data to further investigate the presence of acute tolerance and assess the impact of low MPH doses on its efficacy.

Quantitative Characterization of the Smoothness of Extended-release Methylphenidate Pharmacokinetic Profiles

OBJECTIVE

Extended-release methylphenidate (ER-MPH) formulations used to treat attention deficit hyperactivity disorder (ADHD) have complex pharmacokinetic (PK) profiles, resulting from differing ratios of immediate-release and extended-release components and/or their site of absorption. This study aimed to evaluate the smoothness of PK curves of ER-MPHs.

DESIGN

The integral of the second derivative squared was evaluated for modeled PK curves, with smaller values indicating a smoother curve. The calculated smoothness of each PK curve was normalized by dividing by Cmax 2 to derive a normalized smoothness parameter appropriate across the dose range of each formulation. Calculations used modeled PK curves from 100mg delayed-release and ER-MPH (DR/ER-MPH), 54mg osmotic release oral system MPH (OROS MPH), 60mg MPH controlled-release delivery (MPH CD), 60mg ER-MPH oral suspension (MEROS), 20mg ER dexmethylphenidate (d-MPH ER), and 60mg multilayer-release MPH (MLR-MPH).

RESULTS

The Cmax2-normalized smoothness value was consistent across DR/ER-MPH doses, allowing for relevant comparisons across formulations. Normalized smoothness values differed widely; the lowest normalized smoothness was 0.05 with DR/ER-MPH and ranged up to 9.56 with d-MPH ER.

CONCLUSION

DR/ER-MPH demonstrated a smoother PK profile compared to the highest dose of other ER-MPH formulations. While the benefits of a smooth PK profile remain to be tested clinically, having fewer peaks and troughs has been hypothesized to reduce waxing and waning of therapeutic effects throughout the day, and more gradual changes in MPH plasma levels have been hypothesized to lower the risk of likeability and potentially abate afternoon symptom rebound.

Stimulants

Stimulants have been available for the treatment of attention-deficit/hyperactivity disorder (ADHD) for more than 70 years and are the most effective medications available. During the past 2 decades, several new immediate-release (IR) and extended-release methylphenidate (MPH) and amphetamine (AMPH) formulations have become available. These products differ by dose form (capsules, tablets, oral suspensions, oral disintegrating tablets, and patch), by onset and duration of effect, and by bioavailability. The side effect profile is generally similar for all compounds. Although the products are similar, individual patients may have a better response or tolerability to a particular class (MPH or AMPH) or formulation.

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.

A Post Hoc Comparison of Prior ADHD Medication Dose and Optimized Delayed-release and Extended-release Methylphenidate Dose in a Pivotal Phase III Trial

PURPOSE

HLD200 is the first evening-dosed, delayed-release and extended-release methylphenidate (DR/ER-MPH) designed to delay initial release of MPH and provide treatment effects throughout the day and into the evening for individuals with attention-deficit/hyperactivity disorder (ADHD). Because DR/ER-MPH is uniquely absorbed in the colon, it cannot be substituted for other ADHD medications on a milligram-per-milligram basis. To provide clinicians with a target dose range for DR/ER-MPH when transitioning patients from a prior ADHD medication, dose conversion ratios (DCRs) between prior medication doses and optimized doses of DR/ER-MPH were determined post hoc from a pivotal Phase III study of children (aged 6-12 years) with ADHD.

METHODS

DR/ER-MPH doses were optimized over a 6-week open-label period. DCRs were calculated between optimized doses of DR/ER-MPH at week 6 and prior stable doses of ADHD medication.

FINDINGS

Mean DCRs ranged from 1.8 to 4.3 for optimized DR/ER-MPH dose versus previous stable dose for individuals taking an extended-release stimulant monotherapy. DCRs for those taking an immediate-release stimulant monotherapy ranged from 4.7 to 6.0.

IMPLICATIONS

In a Phase III trial of children with ADHD, optimized doses of DR/ER-MPH were higher than doses of prior ADHD medications, but the adverse event profile was consistent with that of other MPHs. Higher DCRs compared with those predicted by bioavailability differences are consistent with a predicted dose-dependent duration of effect for DR/ER-MPH: with increasing doses, absorption is extended but with an attenuated increase in C_max compared with MPH formulations absorbed in the upper bowel. These data may help guide clinicians to optimize DR/ER-MPH doses. ClinicalTrials.gov identifier: NCT02493777.