Patient-specific in vitro drug release testing coupled with in silico PBPK modeling to forecast the in vivo performance of oral extended-release levodopa formulations in Parkinson's disease patients.

Biorelevant in vitro release models are valuable analytical tools for oral drug development but often tailored to gastrointestinal conditions in 'average' healthy adults. However, predicting in vivo performance in individual patients whose gastrointestinal conditions do not match those of healthy adults would be of great value for optimizing oral drug therapy for such patients. This study focused on establishing patient-specific in vitro and in silico models to predict the in vivo performance of levodopa extended-release products in Parkinson's disease patients. Current knowledge on gastrointestinal conditions in these patients was incorporated into model development. Relevant in vivo pharmacokinetic data and patient-specific in vitro release data from a novel in vitro test setup were integrated into patient-specific physiologically-based pharmacokinetic models. AUC, cmax and tmax of the computed plasma profiles were calculated using PK-Sim®. For the products studied, levodopa plasma concentration-time profiles modeled using this novel approach compared far better with published average plasma profiles in Parkinson's disease patients than those derived from in vitro release data obtained from the 'average' healthy adult setup. Although further work is needed, results of this study highlight the importance of addressing patient-specific gastrointestinal conditions when aiming to predict drug release in such specific patient groups.

Review of paediatric gastrointestinal physiology relevant to the absorption of orally administered medicines.

Despite much progress in regulations to improve paediatric drug development, there remains a significant need to develop better medications for children. For the design of oral dosage forms, a detailed understanding of the specific gastrointestinal (GI) conditions in children of different age categories and how they differ from GI conditions in adults is essential. Several review articles have been published addressing the ontogeny of GI characteristics, including luminal conditions in the GI tract of children. However, the data reported in most of these reviews are of limited quality because (1) information was cited from very old publications and sometimes low quality sources, (2) data gaps in the original data were filled with textbook knowledge, (3) data obtained on healthy and sick children were mixed, (4) average data obtained on groups of patients were mixed with data obtained on individual patients, and (5) results obtained using investigative techniques that may have altered the outcome of the respective studies were considered. Consequently, many of these reviews draw conclusions that may be incorrect. The aim of the present review was to provide a comprehensive and updated overview of the available original data on the ontogeny of GI luminal conditions relevant to oral drug absorption in the paediatric population. To this end, the PubMed and Web of Science metadatabases were searched for appropriate studies that examined age-related conditions in the oral cavity, esophagus, stomach, small intestine, and colon. Maturation was observed for several GI parameters, and corresponding data sets were identified for each paediatric age group. However, it also became clear that the ontogeny of several GI traits in the paediatric population is not yet known. The review article provides a robust and valuable data set for the development of paediatric in vitro and in silico biopharmaceutical tools to support the development of age-appropriate dosage forms. In addition, it provides important information on existing data gaps and should provide impetus for further systematic and well-designed in vivo studies on GI physiology in children of specific age groups in order to close existing knowledge gaps and to sustainably improve oral drug therapy in children.

A Biopredictive In Vitro Approach for Assessing Compatibility of a Novel Pediatric Hydrocortisone Drug Product within Common Pediatric Dosing Vehicles.

PURPOSE: The objective of the present work was to screen whether a novel pediatric hydrocortisone granule formulation can be co-administered with common food matrices and liquids. METHODS: Pediatric hydrocortisone granules were studied using a biopredictive in vitro approach. Experiments included an in situ chemical compatibility study of active ingredient and drug product with liquid dosing vehicles and soft foods commonly ingested by infants, pre-school- and school children. Drug solubility and stability experiments in the different vehicle types and, drug release/dissolution experiments mimicking age-related pediatric gastric conditions after administering the hydrocortisone granules together with the dosing vehicles and after different exposure/mixing times were performed. RESULTS: In the simulated dosing scenarios applied in dissolution experiments, in vitro dissolution in gastric conditions was rapid and complete. Results of the chemical compatibility/stability studies indicated that mixing with the different dosing vehicles studied should not be an issue regarding drug degradation products. CONCLUSIONS: A novel in vitro approach ensuring a proper risk assessment of the use of dosing vehicles in the administration of pediatric dosage forms was established and applied to a novel pediatric hydrocortisone drug product. The studied dosing vehicles were shown to not alter performance of the drug product and are thus considered suitable for administration with hydrocortisone granules. Graphical abstract.

Biorelevant in vitro assessment of dissolution and compatibility properties of a novel paediatric hydrocortisone drug product following exposure of the drug product to child-appropriate administration fluids.

Alkindi® is a novel oral multi-particulate taste-masked formulation of hydrocortisone for use in children with the rare disease adrenal insufficiency. The objective of the present work was to study the biorelevant dissolution and compatibility properties of Alkindi® granules following exposure to administration fluids including breast milk, artificial milk, whole milk and water. To provide in vitro data for a representative patient collective, dosing conditions in neonates, infants and pre-school children were assessed. Experiments included the physicochemical characterisation of the different administration fluids, hydrocortisone solubility experiments and, dissolution experiments in which initial gastric conditions after the administration of a 0.5 or 5 mg dose with 50-200 mL fluid were simulated. The total duration of the dissolution experiments was 240 min to screen both dissolution and compatibility with the different fluids. Dissolution of the 0.5 mg dose was fast and complete in all scenarios, i.e. ≥80% of the dose was released in the neonate and the infant scenario and ≥75% in the pre-school children setup within 30 min. Results for the 5 mg dose were ∼5-10% lower in all simulated patient scenarios. The results obtained in the present study confirm the compatibility and in-use chemical stability of Alkindi® with all studied dosing matrices and that in vivo dissolution and bioavailability of the product will not be affected by the composition of the co-administered fluids studied.

A review of patient-specific gastrointestinal parameters as a platform for developing in vitro models for predicting the in vivo performance of oral dosage forms in patients with Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease that presents with visible motor symptoms, but that is accompanied by several additional symptoms, including gastrointestinal symptoms that may affect pharmacokinetics of oral medications. A detailed understanding of the nature of PD-specific gastrointestinal parameters and of how they may affect drug release of orally administered dosage forms seems to be essential information for developing better oral PD medications. The availability of bio-predictive drug release models simulating PD-specific gastrointestinal parameters would also be beneficial for this purpose. The focus of the present literature review was to determine PD-specific gastrointestinal parameters that will allow for the development of a test methodology simulating the gastrointestinal passage of orally administered medications in PD patients. Whereas for some gastrointestinal segments there is quite a reasonable set of data available on fluid volumes, motility and passage times, for others there is still a big lack in information that would be required for simulating a detailed gastrointestinal passage in a PD patient. The latter is particularly true for potential disease-related changes in gastrointestinal fluid composition. However, with the availability of novel non-invasive diagnostic options there is a chance of obtaining more information in the near future.

Development and Validation of a Robust and Efficient HPLC Method for the Simultaneous Quantification of Levodopa, Carbidopa, Benserazide and Entacapone in Complex Matrices.

PURPOSE: A variety of fixed-dose combination products is used in the therapy of Parkinson Disease. However, to date a proper analytical method applicable for comparative screening of different antiparkinson products was not available. The objective of the present work was thus to develop and validate an analytical method for the simultaneous quantification of levodopa, carbidopa, benserazide and entacapone. The method should be applicable for quantifying samples from drug release experiments with marketed products and prototype formulations performed under compendial and biorelevant test conditions. METHODS: A fast and robust method applicable for separation and quantification of the four compounds was developed and validated according to International Conference on Harmonization guidelines. Method validation covered applicability to a wide concentration range of all compounds and peak separation in complex sample matrices such as biorelevant dissolution media. RESULTS: The compounds were successfully separated by using a gradient elution method on an endcapped LiChrospher 100 RP-18 (250 x 4.6 mm, 5 µm) column coupled with a LiChrospher 100 RP-18 precolumn (4 x 4 mm, 5 µm) at a column temperature of 35.0 °C and a flow rate of 1.50 mL/min. The injection volume was 30 µL and the detection wavelengths were 280 and 210 nm, respectively. For all drug/media combinations the method was linear (r2 > 0.999) for a concentration range corresponding to 1.25 - 125 % label claim (i.e. 200 mg levodopa/entacapone and 50 mg carbidopa/benserazide) released. All other validation parameters were in the specified limits over the same concentration range. CONCLUSION: The new method allows for robust and fast separation of levodopa, carbidopa, benserazide and entacapone without any interference caused by excipients or ingredients of compendial and biorelevant dissolution media and thus presents a valuable tool in both formulation development and in vitro drug release screening of numerous fixed-dose combinations of antiparkinson drugs. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.