The Provisional No-Effect Threshold of Sugar Alcohols on Oral Drug Absorption Estimated by Physiologically Based Biopharmaceutics Model

Indium-Mediated Acyloxyallylation-Based Synthesis of Galacto-Configured Higher-Carbon Sugar Alcohols as Potential Phase Change Materials

Sugar alcohols fulfilling specific structural requirements are a substance class with great potential as organic phase change materials (PCMs). Within this work, we demonstrate the indium-mediated acyloxyallylation (IMA) as a useful strategy for the synthesis of higher-carbon sugar alcohols of the galacto-family featuring all hydroxyl groups in a 1,3-anti-relationship with three major synthetic achievements: first, the dihydroxylation of the IMA-derived allylic sugar derivates was systematically studied in terms of diastereoselectivity, revealing a high degree of substrate control toward anti-addition. Second, we demonstrated the use of a "double Mitsunobu" reaction, inverting the stereochemistry of terminal diols. Third, the IMA toolbox was expanded to accomplish the synthesis of derivatives with up to 10 carbon atoms from particularly unreactive aldoses. Thermal investigations of all synthesized sugar alcohols, including examples with exclusive 1,3-anti- and suboptimal 1,3-syn-relationships as well as even and odd numbers of carbon atoms, were performed. We observed clear trends in melting points and thermal storage densities and discovered limitations of organic substances in this class with melting points above 240 °C as PCMs in terms of thermal stability. With our study, we provide insights into the dependence of thermal properties on structural features, thus contributing to further understanding of organic PCMs for thermal energy storage applications.

Quantitative analysis of gastrointestinal fluid absorption and secretion to estimate luminal fluid dynamics in rats

The drug absorption profile is dependent on the luminal drug concentration, which in turn is influenced by the gastrointestinal (GI) fluid dynamics. In the present study, therefore, we aimed to examine the luminal fluid dynamics by kinetically analyzing fluid absorption and secretion along the GI tract in rats using the in situ closed-loop technique with non-absorbable fluorescein isothiocyanate-dextran 4000 (FD-4) and tritium water labeling ([3H]water) under different osmotic conditions. We found that the luminal fluid volume in the jejunum and ileum, but not the colon, gradually decreased and reached a steady state. In contrast, [3H]water almost completely disappeared in all intestinal regions. Kinetic analysis revealed the following rank order for the rate constant of fluid secretion: jejunum > ileum > colon, whereas a negligible regional difference was observed in the rate constant of fluid absorption. Fluid secretion under an isosmotic condition (300 mOsm/kg) was higher than that at 0 mOsm/kg in all intestinal regions, though no significant changes in fluid absorption were observed. Thus, the fluid secretion process appears to be the major determinant of the regional differences in GI fluid dynamics. Our findings indicate that the luminal fluid volume is altered as a result of water ingestion, absorption, and secretion, and finally reaches an apparent steady state, which is regulated mainly by the process of fluid secretion.

Mechanisms affecting the biopharmacological properties of saffron active ingredients based on anti-inflammatory activity

To explore the mechanisms affecting the biopharmacological properties of the active components of saffron. Ultrasonic extraction technique was applied to extract the active components from safflower materials and combined with molecular docking technique to screen four safflower anti-inflammatory active components, naiophenol-3-0-rutinoside, kaempferol-3-O-glucoside, quercetin and lignan. In order to understand the mechanism of the influence of its biopharmaceutical properties, the changes of the solubility and permeability parameters of the anti-inflammatory active components of safflower were obtained by using the classical shaking bottle method and the body enteric irrigation method. The compound environment had a great influence on the solubility of single active ingredient. The calculated results of the dose number of all ingredients were greater than 1, and the solubility properties were all high solubility. The absorption parameters and osmotic coefficients of kaempferol-3-O-glucoside and lignan varied insignificantly under different concentration conditions, while each osmotic coefficient of kaempferol-3-O-rutinoside and quercetin showed a positive proportional decreasing trend. In addition, the osmotic coefficients of the three components except kaempferol-3-O-glucoside did not change with environmental changes, and the overall anti-inflammatory active ingredient absorption mechanisms included both passive diffusion and active transport. The two biopharmaceutical properties of the solubility and permeability of the active ingredients of Safflower can be changed under the influence of the application environment and drug concentration. In the pharmaceutical process, the preparation means can be optimized from this aspect to achieve the purpose of improving the clinical efficacy of Safflower anti-inflammatory drugs.

Lowly-buffered biorelevant dissolution testing is not necessarily biopredictive of human bioequivalence study outcome: Relationship between dissolution and pharmacokinetics

It has been revealed that buffer capacity of aspirated human intraluminal fluid is much lower than that of in vitro compendial dissolution media. Since buffer capacity significantly alters the dissolution profile of certain drug products, dissolution testing in highly buffered media dictates poor predictability of in vivo drug performance. To mitigate this inconsistency, low buffer capacity medium was suggested as an in vivo representation (biorelevant dissolution testing). The purpose of this study was to characterize the dissolution profiles of enteric-coated drug products in different buffer capacity media in a flow through cell dissolution apparatus, and to evaluate the in vivo predictability of human bioequivalence study outcomes conducted in the fasted state. It was confirmed that the lower the buffer capacity of dissolution media, the higher the discriminatory power of esomeprazole magnesium hydrate enteric-coated pellets, reflecting human bioequivalence failure. In the meantime, two duloxetine hydrochloride enteric-coated pellets also exhibited distinct dissolution profiles in such a lowly buffered medium despite the fact that these two are bioequivalent in human. Biopharmaceutical and pharmacokinetic characteristics comparison suggested that low intestinal permeability and small systemic elimination rate of duloxetine hinders the clear impact of different dissolution profile on its in vivo performance. These data suggest that dissolution comparison in physiologically-relevant low buffer capacity media is not always indicative of human bioequivalence. Instead, biopharmaceutical and pharmacokinetic aspects must be taken into consideration to make biorelevant dissolution testing biopredictive.

The Rat Continuous Intestine Model Predicts the Impact of Particle Size and Transporters on the Oral Absorption of Glyburide

Oral drug absorption is known to be impacted by the physicochemical properties of drugs, properties of oral formulations, and physiological characteristics of the intestine. The goal of the present study was to develop a mathematical model to predict the impact of particle size, feeding time, and intestinal transporter activity on oral absorption. A previously published rat continuous intestine absorption model was extended for solid drug absorption. The impact of active pharmaceutical ingredient particle size was evaluated with glyburide (GLY) as a model drug. Two particle size suspensions of glyburide were prepared with average particle sizes of 42.7 and 4.1 μm. Each suspension was dosed as a single oral gavage to male Sprague Dawley rats, and concentration-time (C-t) profiles of glyburide were measured with liquid chromatography coupled with tandem mass spectrometry. A continuous rat intestine absorption model was extended to include drug dissolution and was used to predict the absorption kinetics of GLY depending on particle size. Additional literature datasets of rat GLY formulations with particle sizes ranging from 0.25 to 4.0 μm were used for model predictions. The model predicted reasonably well the absorption profiles of GLY based on varying particle size and varying feeding time. The model predicted inhibition of intestinal uptake or efflux transporters depending on the datasets. The three datasets used formulations with different excipients, which may impact the transporter activity. Model simulations indicated that the model provides a facile framework to predict the impact of transporter inhibition on drug C-t profiles. Model simulations can also be conducted to evaluate the impact of an altered intestinal lumen environment. In conclusion, the rat continuous intestine absorption model may provide a useful tool to predict the impact of varying drug formulations on rat oral absorption profiles.

The Use of Physiologically Based Pharmacokinetic Analyses-in Biopharmaceutics Applications -Regulatory and Industry Perspectives

The use of physiologically based pharmacokinetic (PBPK) modeling to support the drug product quality attributes, also known as physiologically based biopharmaceutics modeling (PBBM) is an evolving field and the interest in using PBBM is increasing. The US-FDA has emphasized on the use of patient centric quality standards and clinically relevant drug product specifications over the years. Establishing an in vitro in vivo link is an important step towards achieving the goal of patient centric quality standard. Such a link can aid in constructing a bioequivalence safe space and establishing clinically relevant drug product specifications. PBBM is an important tool to construct a safe space which can be used during the drug product development and lifecycle management. There are several advantages of using the PBBM approach, though there are also a few challenges, both with in vitro methods and in vivo understanding of drug absorption and disposition, that preclude using this approach and therefore further improvements are needed. In this review we have provided an overview of experience gained so far and the current perspective from regulatory and industry point of view. Collaboration between scientists from regulatory, industry and academic fields can further help to advance this field and deliver on promises that PBBM can offer towards establishing patient centric quality standards.

Evaluation of Excipient Risk in BCS Class I and III Biowaivers

The objective of this review article is to summarize literature data pertinent to potential excipient effects on intestinal drug permeability and transit. Despite the use of excipients in drug products for decades, considerable research efforts have been directed towards evaluating their potential effects on drug bioavailability. Potential excipient concerns stem from drug formulation changes (e.g., scale-up and post-approval changes, development of a new generic product). Regulatory agencies have established in vivo bioequivalence standards and, as a result, may waive the in vivo requirement, known as a biowaiver, for some oral products. Biowaiver acceptance criteria are based on the in vitro characterization of the drug substance and drug product using the Biopharmaceutics Classification System (BCS). Various regulatory guidance documents have been issued regarding BCS-based biowaivers, such that the current FDA guidance is more restrictive than prior guidance, specifically about excipient risk. In particular, sugar alcohols have been identified as potential absorption-modifying excipients. These biowaivers and excipient risks are discussed here.

An Assessment of Occasional Bio-Inequivalence for BCS1 and BCS3 Drugs: What are the Underlying Reasons?

Despite having adequate solubility properties, bioequivalence (BE) studies performed on immediate release formulations containing BCS1/3 drugs occasionally fail. By systematically evaluating a set of 17 soluble drugs where unexpected BE failures have been reported and comparing to a set of 29 drugs where no such reports have been documented, a broad assessment of the risk factors leading to BE failure was performed. BE failures for BCS1/3 drugs were predominantly related to changes in C_max rather than AUC. C_max changes were typically modest, with minimal clinical significance for most drugs. Overall, drugs with a sharp plasma peak were identified as a key factor in BE failure risk. A new pharmacokinetic term (t½C_max) is proposed to identify drugs at higher risk due to their peak plasma profile shape. In addition, the analysis revealed that weak acids, and drugs with particularly high gastric solubility are potentially more vulnerable to BE failure, particularly when these features are combined with a sharp C_max peak. BCS3 drugs, which are often characterised as being more vulnerable to BE failure due to their potential for permeation and transit to be altered, particularly by excipient change, were not in general at greater risk of BE failures. These findings will help to inform how biowaivers may be optimally applied in the future.

Potential pharmacokinetic interaction between orally administered drug and osmotically active excipients in pediatric polypharmacy

Poorly absorbable sugar alcohols (e.g., mannitol, sorbitol, and maltitol) are the excipients frequently contained in pediatric dosage forms. Due to their osmotically active properties, certain amount of sugar alcohols reportedly reduces oral bioavailability of concomitant drugs. This fact implies the possible pharmacokinetic interaction between orally administered drug and sugar alcohols which are present in other concomitant medications. The purpose of this study was to identify the possibility and likeliness of the osmotically active excipient-induced pharmacokinetic interaction in pediatric polypharmacy. Previously developed in silico model that captured the osmotic effect of sugar alcohols in adults was expanded to pediatric population. This mathematical model successfully explained the impaired bioavailability of lamivudine by the co-administered sorbitol in other dosage forms. In the meantime, sugar alcohol contents in marketed pediatric dosage forms were investigated by reverse engineering technology. Considering the critical administration dose of sugar alcohols estimated by in silico model, it was revealed that 25 out of 153 pediatric dosage forms were identified as possible perpetrators even under the approved administration and dosage in Japan. This study shed light on the potential pharmacokinetic interaction that cannot be dismissed throughout the pediatric pharmaceutical dosage form design and development.

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Metformin Hydrochloride

Data are examined regarding possible waiver of in vivo bioequivalence testing (i.e. biowaiver) for approval of metformin hydrochloride (metformin) immediate-release solid oral dosage forms. Data include metformin's Biopharmaceutics Classification System (BCS) properties, including potential excipient interactions. Metformin is a prototypical transporter-mediated drug and is highly soluble, but only 50% of an orally administered dose is absorbed from the gut. Therefore, metformin is a BCS Class III substance. A BCS-based approval approach for major changes to marketed products and new generics is admissible if test and reference dosage forms have the identical active pharmaceutical ingredient and if in vitro dissolution from both are very rapid (i.e. at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Recent International Council for Harmonisation BCS guidance indicates all excipients for Class III biowaivers are recommended to be qualitatively the same and quantitatively similar (except for preservatives, flavor agents, colorant, or capsule shell or film coating excipients). However, despite metformin being a prototypical transporter-mediated drug, there is no evidence that commonly used excipients impact metformin absorption, such that this restriction on excipients for BCS III drugs merits regulatory relief. Commonly used excipients in usual amounts are not likely to impact metformin absorption.