Biopharmaceutical considerations in paediatrics with a view to the evaluation of orally administered drug products - a PEARRL review

Unmet technological demands in orodispersible films for age-appropriate paediatric drug delivery

Age-appropriateness of a formulation is the ability to deliver variable but accurate doses to the paediatric population in a safe and acceptable manner to improve medical adherence and reduce medication errors. Paediatric drug delivery is a challenging area of formulation research due to the existing gap in knowledge. This includes the unknown safety of excipients in the paediatric population, the need for an age-appropriate formulation, the lack of an effective taste-masking method and the lack of paediatric pharmacokinetic data and patient acceptability. It is equally important to establish methods for predicting the biopharmaceutical performance of a paediatric formulation as a function of age. Overcoming the challenges of existing technologies and providing custom-made solutions for the development of age-appropriate formulation is, therefore, a daunting task. Orodispersible films (ODF) are promising as age-appropriate formulations, an unmet need in paediatric drug delivery. New technological improvements in taste masking, improving solubility and rate of dissolution of insoluble drugs, the flexibility of dosing and extemporaneous preparation of these films in a hospital good manufacturing practises (GMP) setup using 3D printing can increase its acceptance among clinicians, patients and caregivers. The current review discusses the problems and possibilities in ODF technology to address the outstanding issues of age-appropriateness, which is the hallmark of patient acceptance and medical adherence in paediatrics.

Bioequivalence of 2 Pediatric Formulations of Fexofenadine Hydrochloride Oral Suspension

Fexofenadine hydrochloride (HCl) is a second-generation, nonsedating, histamine H1-receptor antagonist used to manage seasonal allergic rhinitis and chronic idiopathic urticaria. A new oral pediatric suspension of fexofenadine HCl has been developed, with the preservative potassium sorbate replacing parabens. The objective of this phase 1 single-center, open-label, randomized, 2-treatment, full-replicated, 4-period, 2-sequence crossover study in healthy adult volunteers was to assess the bioequivalence of 30 mg of the new oral suspension of fexofenadine HCl (test) versus 30 mg of the marketed pediatric oral suspension of fexofenadine HCl (reference). The replicate design was based on the high intra-individual variability of fexofenadine (>30% on Cmax ). The study comprised 68 randomized and treated volunteers. Plasma concentrations of fexofenadine were similar following the administration of a single dose of each formulation. Cmax , AUClast , AUC, median tmax , and mean t1/2z were similar between administrations of the same fexofenadine formulation and between formulations. A high intra-individual variability was confirmed with both formulations. Bioequivalence of the test and reference fexofenadine HCl formulations was demonstrated as the 90% confidence intervals of the geometric least squares mean ratio for Cmax , AUClast , and AUC of fexofenadine were all within the bioequivalence range of 0.80-1.25. There were no serious adverse events (AEs) or study discontinuations due to treatment-emergent AEs with either fexofenadine HCl formulation. The new paraben-free fexofenadine HCl 30-mg oral suspension and marketed fexofenadine HCl 30-mg pediatric oral suspension are bioequivalent under fasting conditions, with no safety concerns and a safety profile consistent with the known profile of fexofenadine.

Quantification of drug metabolising enzymes and transporter proteins in the paediatric duodenum via LC-MS/MS proteomics using a QconCAT technique

Characterising the small intestine absorptive membrane is essential to enable prediction of the systemic exposure of oral formulations. In particular, the ontogeny of key intestinal Drug Metabolising Enzymes and Transporter (DMET) proteins involved in drug disposition needs to be elucidated to allow for accurate prediction of the PK profile of drugs in the paediatric cohort. Using pinch biopsies from the paediatric duodenum (n = 36; aged 11 months to 15 years), the abundance of 21 DMET proteins and two enterocyte markers were quantified via LC-MS/MS. An established LCMS nanoflow method was translated to enable analysis on a microflow LC system, and a new stable-isotope-labelled QconCAT standard developed to enable quantification of these proteins. Villin-1 was used to standardise abundancy values. The observed abundancies and ontogeny profiles, agreed with adult LC-MS/MS-based data, and historic paediatric data obtained via western blotting. A linear trend with age was observed for duodenal CYP3A4 and CES2 only. As this work quantified peptides on a pinch biopsy coupled with a microflow method, future studies using a wider population range are very feasible. Furthermore, this DMET ontogeny data can be used to inform paediatric PBPK modelling and to enhance the understanding of oral drug absorption and gut bioavailability in paediatric populations.

Integration of Biorelevant Pediatric Dissolution Methodology into PBPK Modeling to Predict In Vivo Performance and Bioequivalence of Generic Drugs in Pediatric Populations: a Carbamazepine Case Study

This study investigated the impact of gastro-intestinal fluid volume and bile salt (BS) concentration on the dissolution of carbamazepine (CBZ) immediate release (IR) 100 mg tablets and to integrate these in vitro biorelevant dissolution profiles into physiologically based pharmacokinetic modelling (PBPK) in pediatric and adult populations to determine the biopredictive dissolution profile. Dissolution profiles of CBZ IR tablets (100 mg) were generated in 50-900 mL biorelevant adult fasted state simulated gastric and intestinal fluid (Ad-FaSSGF and Ad-FaSSIF), also in three alternative compositions of biorelevant pediatric FaSSGF and FaSSIF medias at 200 mL. This study found that CBZ dissolution was poorly sensitive to changes in the composition of the biorelevant media, where dissimilar dissolution (F2 = 46.2) was only observed when the BS concentration was changed from 3000 to 89 μM (Ad-FaSSIF vs Ped-FaSSIF 50% 14 BS). PBPK modeling demonstrated the most predictive dissolution volume and media composition to forecast the PK was 500 mL of Ad-FaSSGF/Ad-FaSSIF media for adults and 200 mL Ped-FaSSGF/FaSSIF media for pediatrics. A virtual bioequivalence simulation was conducted by using Ad-FaSSGF and/or Ad-FaSSIF 500 mL or Ped-FaSSGF and/or Ped-FaSSIF 200 mL dissolution data for CBZ 100 mg (reference and generic test) IR product. The CBZ PBPK models showed bioequivalence of the product. This study demonstrates that the integration of biorelevant dissolution data can predict the PK profile of a poorly soluble drug in both populations. Further work using more pediatric drug products is needed to verify biorelevant dissolution data to predict the in vivo performance in pediatrics.

Usefulness of the Beagle Model in the Evaluation of Paracetamol and Ibuprofen Exposure after Oral Administration to Pediatric Populations: An Exploratory Study

The present study aimed to explore the usefulness of beagle dogs in combination with physiologically based pharmacokinetic (PBPK) modeling in the evaluation of drug exposure after oral administration to pediatric populations at an early stage of pharmaceutical product development. An exploratory, single-dose, crossover bioavailability study in six beagles was performed. A paracetamol suspension and an ibuprofen suspension were coadministered in the fasted-state conditions, under reference-meal fed-state conditions, and under infant-formula fed-state conditions. PBPK models developed with GastroPlus v9.7 were used to inform the extrapolation of beagle data to human infants and children. Beagle-based simulation outcomes were compared with published human-adult-based simulations. For paracetamol, fasted-state conditions and reference-meal fed-state conditions in beagles appeared to provide adequate information for the applied scaling approach. Fasted-state and/or reference-meal fed-state conditions in beagles appeared suitable to simulate the performance of ibuprofen suspension in pediatric populations. Contrary to human-adult-based translations, extrapolations based on beagle data collected under infant-formula fed-state conditions appeared less useful for informing simulations of plasma levels in pediatric populations. Beagle data collected under fasted and/or reference-meal fed-state conditions appeared to be useful in the investigation of pediatric product performance of the two investigated highly permeable and highly soluble drugs in the upper small intestine. The suitability of the beagle as a preclinical model to understand pediatric drug product performance under different dosing conditions deserves further evaluation with a broader spectrum of drugs and drug products and comparisons with pediatric in vivo data.

Understanding the Impact of Age-Related Changes in Pediatric GI Solubility by Multivariate Data Analysis

The aim of this study was to understand drug solubilization as a function of age and identify drugs at risk of altered drug solubility in newborns and young infants in comparison to adults. Multivariate statistical analysis was used to understand drug solubilization as a function of drug’s physicochemical properties and the composition of gastrointestinal fluids. The solubility of seven poorly soluble compounds was assessed in adult and age-specific fasted and fed state biorelevant media. Partial least squares regression (PLS-R) was used to assess the influence of (i) drug physicochemical properties and (ii) age-related changes in simulated GI fluids, as well as (iii) their interactions, on the pediatrics-to-adult solubility ratio (Sp/Sa (%)). For five out of seven of the compounds investigated, Sp/Sa (%) values fell outside of the 80–125% limits in at least one of the pediatric media. Lipophilicity was responsible for driving drug solubility differences between adults and children in all the biorelevant media investigated, while drug ionization was most relevant in the fed gastric media, and the fasted/fed intestinal media. The concentration of bile salts and lecithin in the fasted and fed intestinal media was critical in influencing drug solubility, while food composition (i.e., cow’s milk formula vs. soy formula) was a critical parameter in the fed gastric state. Changes in GI fluid composition between younger pediatric patients and adults can significantly alter drug luminal solubility. The use of pediatric biorelevant media can be helpful to identify the risk of altered drug solubilization in younger patients during drug development.

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.

Performance Evaluation of Montelukast Pediatric Formulations: Part II - a PBPK Modelling Approach

This study aimed to build a physiologically based pharmacokinetic (PBPK) model coupled with age-appropriate in vitro dissolution data to describe drug performance in adults and pediatric patients. Montelukast sodium was chosen as a model drug. Two case studies were investigated: case study 1 focused on the description of formulation performance from adults to children; case study 2 focused on the description of the impact of medicine co-administration with vehicles on drug exposure in infants. The PBPK model for adults and pediatric patients was developed in Simcyp^® v18.2 informed by age-appropriate in vitro dissolution results obtained in a previous study. Oral administration of montelukast was simulated with the ADAM™ model. For case study 1, the developed PBPK model accurately described montelukast exposure in adults and children populations after the administration of montelukast chewable tablets. Two-stage dissolution testing in simulated fasted gastric to intestinal conditions resulted in the best description of in vivo drug performance in adults and children. For case study 2, a good description of in vivo drug performance in infants after medicine co-administration with vehicles was achieved by incorporating in vitro drug dissolution (under simulated fasted gastric to fed intestinal conditions) into a fed state PBPK model with consideration of the in vivo dosing conditions (mixing of formulation with applesauce or formula). The case studies presented demonstrate how a PBPK absorption modelling strategy can facilitate the description of drug performance in the pediatric population to support decision-making and biopharmaceutics understanding during pediatric drug development.

Performance Evaluation of Montelukast Pediatric Formulations: Part I-Age-Related In Vitro Conditions

This study aimed to explore the potential of biopharmaceutics in vitro tools to predict drug product performance in the pediatric population. Biorelevant dissolution set-ups were used to predict how age and medicine administration practices affect the in vitro dissolution of oral formulations of a poorly water-soluble compound, montelukast. Biorelevant age-appropriate dissolution studies of Singulair^® (granules and chewable tablets) were conducted with the µDISS profiler™, USP 4 apparatus, USP 2 apparatus, and mini-paddle apparatus. Biorelevant simulating fluids representative of adult and pediatric conditions were used in the dissolution studies. The biorelevant dissolution conditions were appropriately selected (i.e. volumes, transit times, etc.) to mimic the gastrointestinal conditions of each of the subpopulations tested. Partial least squares regression (PLS-R) was performed to understand the impact of in vitro variables on the dissolution of montelukast. Montelukast dissolution was significantly affected by the in vitro hydrodynamics used to perform the dissolution tests (µDISS profiler™: positive effect); choice of simulation of gastric (negative effect) and/or intestinal conditions (positive effect) of the gastrointestinal tract; and simulation of prandial state (fasted state: negative effect, fed state: positive effect). Age-related biorelevant dissolution of Singulair^® granules predicted the in vivo effect of the co-administration of the formulation with applesauce and formula in infants. This study demonstrates that age-appropriate biorelevant dissolution testing can be a valuable tool for the assessment of drug performance in the pediatric population.

Quantification of Fluid Volume and Distribution in the Paediatric Colon via Magnetic Resonance Imaging

Previous studies have used magnetic resonance imaging (MRI) to quantify the fluid in the stomach and small intestine of children, and the stomach, small intestine and colon of adults. This is the first study to quantify fluid volumes and distribution using MRI in the paediatric colon. MRI datasets from 28 fasted (aged 0-15 years) and 18 fluid-fed (aged 10-16 years) paediatric participants were acquired during routine clinical care. A series of 2D- and 3D-based software protocols were used to measure colonic fluid volume and localisation. The paediatric colon contained a mean volume of 22.5 mL ± 41.3 mL fluid, (range 0-167.5 mL, median volume 0.80 mL) in 15.5 ± 17.5 discreet fluid pockets (median 12). The proportion of the fluid pockets larger than 1 mL was 9.6%, which contributed to 94.5% of the total fluid volume observed. No correlation was detected between all-ages and colonic fluid volume, nor was a difference in colonic fluid volumes observed based on sex, fed state or age group based on ICH-classifications. This study quantified fluid volumes within the paediatric colon, and these data will aid and accelerate the development of biorelevant tools to progress paediatric drug development for colon-targeting formulations.

Investigating the Critical Variables of Azithromycin Oral Absorption Using In Vitro Tests and PBPK Modeling

Azithromycin is an antibiotic listed in the essential list of medicines for adults and pediatrics. Conflicting evidence has been found regarding azithromycin classification according to the Biopharmaceutics classification system (BCS). The purpose of this study was to identify the critical variables that influence the oral absorption of azithromycin in adults and pediatrics. Azithromycin solubility and dissolution studies (oral suspension) were performed in buffers and biorelevant media simulating the fasted and fed gastrointestinal tract. A PBPK model was developed for azithromycin for healthy adult volunteers and pediatrics (Simcyp® v18.2) informed by in vitro solubility and dissolution studies to predict drug performance after administration of azithromycin as an oral suspension. The developed PBPK model predicted azithromycin plasma concentrations-time profiles after administration of an oral suspension to adults and pediatrics. Sensitivity analysis of solubility vs dose suggests that absorption is independent of solubility within the therapeutic dose range in both adults and pediatrics. The developed PBPK model for adults and pediatrics was consistent with the mechanism of permeation through the intestinal membrane (passive and active processes) being the rate-limiting step of azithromycin's absorption. The physiologically based approach proposed was shown to be useful to determine the factors controlling drug absorption in adults and pediatrics.

Oral delivery of peptide therapeutics in infants: Challenges and opportunities

The vast majority of drugs are not designed or developed for pediatric and infant populations. Peptide drugs, which have become increasingly relevant in the past several decades, are no exception. Unfortunately, nearly all of the 60+ approved peptide drugs are formulated for injection, a particularly unfriendly mode of administration for infants. Although three peptide drugs were recently approved for oral formulations, this major advance in peptide drug delivery is available only for adults. In this review, we consider the current challenges and opportunities for the oral formulation of peptide therapeutics, specifically for infant populations. We describe the strategies that enable oral protein delivery and the potential impact of infant physiology on those strategies. We also detail the limited but encouraging progress towards 1) adapting conventional drug development and delivery approaches to infants and 2) designing novel infant-centric formulations. Together, these efforts underscore the feasibility of oral peptide delivery in infants and provide motivation to increase attention paid to this underserved area of drug delivery and formulation.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Oral biopharmaceutics tools: recent progress from partnership through the Pharmaceutical Education and Research with Regulatory Links collaboration

OBJECTIVES

To summarise key contributions of the Pharmaceutical Education and Research with Regulatory Links (PEARRL) project (2016-2020) to the optimisation of existing and the development of new biopharmaceutics tools for evaluating the in vivo performance of oral drug products during the development of new drugs and at the regulatory level.

KEY FINDINGS

Optimised biopharmaceutics tools: Based on new clinical data, the composition of biorelevant media for simulating the fed state conditions in the stomach was simplified. Strategies on how to incorporate biorelevant in vitro data of bio-enabling drug products into physiologically based pharmacokinetic (PBPK) modelling were proposed. Novel in vitro biopharmaceutics tools: Small-scale two-stage biphasic dissolution and dissolution-permeation setups were developed to facilitate understanding of the supersaturation effects and precipitation risks of orally administered drugs. A porcine fasted state simulated intestinal fluid was developed to improve predictions and interpretation of preclinical results using in vitro dissolution studies. Based on new clinical data, recommendations on the design of in vitro methodologies for evaluating the GI drug transfer process in the fed state were suggested. The optimized design of in vivo studies for investigating food effects: A food effect study protocol in the pig model was established which successfully predicted the food-dependent bioavailability of two model compounds. The effect of simulated infant fed state conditions in healthy adults on the oral absorption of model drugs was evaluated versus the fasted state and the fed state conditions, as defined by regulatory agencies for adults. Using PBPK modelling, the extrapolated fasted and infant fed conditions data appeared to be more useful to describe early drug exposure in infants, while extrapolation of data collected under fed state conditions, as defined by regulators for adults, failed to capture in vivo infant drug absorption.

SUMMARY

Substantial progress has been made in developing an advanced suite of biopharmaceutics tools for streamlining drug formulation screening and supporting regulatory applications. These advances in biopharmaceutics were achieved through networking opportunities and research collaborations provided under the H2020 funded PEARRL project.

Impact of Food and Drink Administration Vehicles on Paediatric Formulation Performance Part 2: Dissolution of Montelukast Sodium and Mesalazine Formulations

Paediatric medicines are not always age-appropriate, causing problems with dosing, acceptability and adherence. The use of food and drinks as vehicles for medicine co-administration is common practice, yet the impact on drug bioavailability, safety and efficacy remains unaddressed. The aim of this study was to use in vitro dissolution testing, under infant simulating conditions, to evaluate the effect of co-administration with vehicles on the dissolution performance of two poorly soluble paediatric drugs. Dissolution studies of mesalazine and montelukast formulations were conducted with mini-paddle apparatus on a two-stage approach: simulated gastric fluid followed by addition of simulated intestinal fluid. The testing scenarios were designed to reflect daily administration practices: direct administration of formulation; formulation co-administered with food and drinks, both immediately after mixing and 4 h after mixing. Drug dissolution was significantly affected by medicine co-administration with vehicles, compared to the direct administration of formulation. Furthermore, differences were observed on drug dissolution when the formulations were mixed with different vehicles of the same subtype. The time between preparation and testing of the drug-vehicle mixture also impacted dissolution behaviour. Drug dissolution was shown to be significantly affected by the physicochemical properties and composition of the vehicles, drug solubility in each vehicle and drug/formulation characteristics. Ultimately, in this study, we show the potential of age-appropriate in vitro dissolution testing as a useful biopharmaceutical tool for estimating drug dissolution in conditions relevant to the paediatric population. The setup developed has potential to evaluate the impact of medicine co-administration with vehicles on paediatric formulation performance.

BCS-based biowaivers: Extension to paediatrics

A BCS-based biowaiver allows extrapolation of drug product bioequivalence (when applicable) based on the BCS class of the drug and in vitro dissolution testing. Drug permeability and solubility considerations for adult BCS might not apply directly to paediatric subpopulations and bridging of adult and paediatric formulations should be undertaken with caution. The aims of this study were to: (i.) identify compounds which would change drug solubility classification in the paediatric population, and (ii.) to assess the risk of extending BCS-based biowaiver criteria into paediatric products of these compounds. Amoxicillin, prednisolone, and amlodipine were selected as the model compounds. Dissolution studies of IR formulations of these compounds were conducted with USP II (paddle) and mini-paddle apparatus, in media of three pHs (pH 1.2, 4.5 and 6.8). Three dissolution setups were tested: (1) 'typical' BCS-based biowaiver conditions, (2) "BE" setup derived from BE study protocols (volume: 250 mL), and (3) "paediatric" setup based on representative volume for the paediatric population (50 mL). Results revealed that extension of regulated BCS-based biowaiver criteria for paediatric application is not as simple as scaling down volumes. It was further shown that BCS-based biowaiver criteria should not be applied when there is the risk of change of the drug solubility class, from the adult to paediatric populations. A deeper knowledge of the paediatric gastrointestinal environment is still lacking and would assist in refining the biopharmaceutical tools needed to appropriately evaluate formulation performance across age groups. This would potentially reduce the number of clinical studies required and speed up formulation development.

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Cephalexin Monohydrate

Literature data and results of experimental studies relevant to the decision to allow waiver of bioequivalence studies in humans for the approval of immediate release solid oral dosage forms containing cephalexin monohydrate are presented. Solubility studies were performed in accordance with the current biowaiver guidelines of the Food and Drug Administration, World Health Organization and European Medicines Agency, taking the degradation at some pH values into consideration. Together with solubility and permeability data for cephalexin monohydrate from the literature, it was demonstrated to be a Biopharmaceutics Classification System Class 1 drug. The pharmacokinetic behavior, results of bioequivalence studies published in the literature, as well as the therapeutic uses, potential toxicity and potential excipient effects on bioavailability were also assessed. Cephalexin has a wide therapeutic index and no bioequivalence problems have been reported. Dissolution studies were run under Biopharmaceutics Classification System-biowaiver conditions for the pure drug and 2 generic formulations available on the German market. Considering all relevant aspects, it was concluded that a biowaiver-based approval for products containing cephalexin monohydrate as the single active pharmaceutical ingredient is scientifically justified, provided that well-established excipients are used in usual amounts and that both test and reference dosage forms meet the guideline criteria of either "rapidly dissolving" or "very rapidly dissolving."

Co-administration of Paediatric Medicines with Food and Drinks in the Context of Their Physicochemical Properties-a Global Perspective on Practices and Recommendations

Medicine co-administration with food or drink vehicles is a common administration practice in paediatrics. The aims of this review were (i) to describe the current recommended strategies for co-administration of paediatric medicines with food and drinks (vehicles); (ii) to compare current administration recommendations from different countries; and (iii) to obtain a global perspective on the rationale behind the choice of recommended vehicle, in the context of the physicochemical properties of the drug and formulation. This study used a defined search strategy on the practices of paediatric medicine co-administration with vehicles, recommended in a commonly used paediatric and neonatal handbook, in addition to the information previously gathered from UK formularies. Logistic regression analysis was performed to further understand the biopharmaceutical basis of the choice of recommended vehicle for medicine co-administration. Differences were identified in the type of vehicles globally recommended for medicine co-administration. Ultimately, a statistical model was developed which provided an understanding on which vehicle is recommended for use with drugs/formulations, with basis on their biopharmaceutical properties. Overall, this review highlights the areas where further information is needed to support standardised procedures and guide the recommendation of age-appropriate and acceptable vehicles for use in the co-administration of paediatric medicines. Unified requirements are needed for harmonisation of the practice of medicine co-administration with vehicles. In vitro and/or in silico tools should be developed to evaluate the potential clinical outcomes of this practice during paediatric drug development.

Considerations for application of biopharmaceutics classification system in chicken: Exemplified by seven drugs classification

Biopharmaceutics Classification System (BCS) has gained broad acceptance in promoting the development of human drugs. To date, the applicability of existing human BCS criteria has not been evaluated in chickens. The objective of this study was to discuss the feasibility of BCS extrapolation between species and establish a preliminary chicken BCS by classifying seven veterinary commonly used drugs including metronidazole, amoxicillin, sulfamethoxazole, sulfadiazine, ciprofloxacin hydrochloride, doxycycline hydrochloride, and trimethoprim. Firstly, we finished the determination of physiological parameters affecting solubility in chickens, including body temperature, gastrointestinal pH, and the fluid volume in the gastrointestinal tract (GI), and the drug is considered highly soluble in chicken BCS when the highest dose strength is soluble in 20.40 ml (fed) or 6.73 ml (fasted) over the pH range of 1-8 at 41°C. Drug solubility classification was based on dose number calculation. Metronidazol and amoxicillin were classed differently under fed and fasted conditions. Secondly, we discussed the effect of ABC transporters (MDCK vs. MDCK-chAbcb1/Abcg2) and pH (5.5 vs. 7.4) on drug permeability and classification. The drug is classified as highly permeable when its permeability is equal to or greater than metoprolol tartrate. Though ABC transporters and pH significantly affected the permeability values of drugs (p < .05), the permeability classification of the drugs has not been changed except for sulfamethoxazole. This work highlights some of the significant challenges that would be encountered in order to develop a chicken BCS, this valuable information could serve as a helpful tool during chicken drugs development and to minimize the potential risks when developing formulations.

Classification of WHO Essential Oral Medicines for Children Applying a Provisional Pediatric Biopharmaceutics Classification System

The objective was using the Essential Medicines List for children by the World Health Organization (WHO) to create a pediatric biopharmaceutics classification system (pBCS) of the oral drugs included in the Essential Medicines List by the World Health Organization and to compare our results with the BCS for adults (aBCS). Several methods to estimate the oral drug dose in different pediatric groups were used to calculate dose number (Do) and solubility (high/low). The estimation of the gastrointestinal water volume was adapted to each pediatric group. Provisional permeability classification was done by comparison of each drug lipophilicity versus metoprolol as the model drug of high permeability. As a result, 24.5% of the included drugs moved from the favorable to unfavorable class (i.e., from high to low solubility). Observed changes point out potential differences in product performance in pediatrics compared to adults, due to changes in the limiting factors for absorption. BCS Class Changes 1 to 2 or 3 to 4 are indicative of drugs that could be more sensitive to the choice of appropriate excipient in the development process. Validating a pBCS for each age group would provide a valuable tool to apply in specific pediatric formulation design by reducing time and costs and avoiding unnecessary pediatric experiments restricted due to ethical reasons. Additionally, pBCS could minimize the associated risks to the use of adult medicines or pharmaceutical compound formulations.

In vitro digestion models to evaluate lipid based drug delivery systems; present status and current trends

During the past two decades, a range of in vitro models simulating the digestion processes occurring in the stomach and small intestine have been developed to characterize lipid based drug delivery systems (LbDDSs). This review describes the presently existing range of in vitro digestion models and their use in the field of oral drug delivery. The models are evaluated in terms of their suitability to assess LbDDSs, and their ability to produce in vitro - in vivo correlations (IVIVCs). While the pH-stat lipolysis model is by far the most commonly utilized in vitro digestion model in relation to characterizing LbDDSs, a series of recent studies have shown a lack of IVIVCs limiting its future use. Presently, no single in vitro digestion model exists which is able to predict the in vivo performance of various LbDDSs. However, recent research has shown the potential of combined digestion-permeation models as well as species specific digestion models.