A Pharmacokinetic Study of Methylphenidate Hydrochloride Multilayer Extended-Release Capsules (Aptensio XR®) in Preschool-Aged Children with Attention-Deficit/Hyperactivity Disorder

Pharmacokinetic Simulation and Area under the Curve Estimation of Drugs Subject to Enterohepatic Circulation

Enterohepatic circulation (EHC) is a complex process where drugs undergo secretion and reabsorption from the intestinal lumen multiple times, resulting in pharmacokinetic profiles with multiple peaks. The impact of EHC on area under the curve (AUC) has been a topic of extensive debate, questioning the suitability of conventional AUC estimation methods. Moreover, a universal model for accurately estimating AUC in EHC scenarios is lacking. To address this gap, we conducted a simulation study evaluating five empirical models under various sampling strategies to assess their performance in AUC estimation. Our results identify the most suitable model for EHC scenarios and underscore the critical role of meal-based sampling strategies in accurate AUC estimation. Additionally, we demonstrate that while the trapezoidal method performs comparably to other models with a large number of samples, alternative models are essential when sample numbers are limited. These findings not only illuminate how EHC influences AUC but also pave the way for the application of empirical models in real-world drug studies.

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.

Long-Term Treatment With Extended-Release Methylphenidate Treatment in Children Aged 4 to <6 Years

OBJECTIVE

To investigate long-term (12-month) safety and symptom control of extended-release methylphenidate (MPH-MLR) in children aged 4 to <6 years after treatment optimization.

METHOD

A total of 90 children aged 4 to <6 years with attention-deficit/hyperactivity disorder (ADHD) were enrolled from 2 MPH-MLR studies. Treatment-emergent adverse events (TEAEs) and ADHD symptom control were assessed in the safety population (n = 89) and modeled with mixed model analyses.

RESULTS

Most TEAEs (89.9%) were rated by investigators as of mild or moderate severity. One serious AE was reported (unrelated to study drug). Ten children discontinued because of TEAEs. Two discontinued because of weight loss; no significant increase in the rate of underweight children from baseline to endpoint was observed. Overall, 18% lost weight and 18% reported decreased appetite. Weight and height z scores and obesity rates decreased significantly from baseline to endpoint. Insomnia was reported (9%); none of these children discontinued. Sleep quality did not change significantly. Hypertension was reported (6.7%); none of these children dropped out. Diastolic, but not systolic, blood pressure increased significantly during the follow-up. Control of ADHD symptoms was maintained throughout follow-up.

CONCLUSION

These data contribute to the understanding of the long-term safety of an extended-release stimulant in children 4 to <6 years of age. The observed risk of a TEAE-related discontinuation was ∼11%. TEAEs were not dose related, and most were of mild to moderate severity. Symptom control was maintained through the year-long study.

CLINICAL TRIAL REGISTRATION INFORMATION

A 12-Month Open Label Safety Study of Aptensio XR® in Children Ages 4-5 Years Diagnosed With ADHD (EF004); https://clinicaltrials.gov; NCT02677519.