The Effect of Capsule-in-Capsule Combinations on In Vivo Disintegration in Human Volunteers: A Combined Imaging and Salivary Tracer Study

Parameterization of Physiologically Based Biopharmaceutics Models: Workshop Summary Report

This Article shares the proceedings from the August 29th, 2023 (day 1) workshop "Physiologically Based Biopharmaceutics Modeling (PBBM) Best Practices for Drug Product Quality: Regulatory and Industry Perspectives". The focus of the day was on model parametrization; regulatory authorities from Canada, the USA, Sweden, Belgium, and Norway presented their views on PBBM case studies submitted by industry members of the IQ consortium. The presentations shared key questions raised by regulators during the mock exercise, regarding the PBBM input parameters and their justification. These presentations also shed light on the regulatory assessment processes, content, and format requirements for future PBBM regulatory submissions. In addition, the day 1 breakout presentations and discussions gave the opportunity to share best practices around key questions faced by scientists when parametrizing PBBMs. Key questions included measurement and integration of drug substance solubility for crystalline vs amorphous drugs; impact of excipients on apparent drug solubility/supersaturation; modeling of acid-base reactions at the surface of the dissolving drug; choice of dissolution methods according to the formulation and drug properties with a view to predict the in vivo performance; mechanistic modeling of in vitro product dissolution data to predict in vivo dissolution for various patient populations/species; best practices for characterization of drug precipitation from simple or complex formulations and integration of the data in PBBM; incorporation of drug permeability into PBBM for various routes of uptake and prediction of permeability along the GI tract.

Impact of advanced age on the gastric emptying of water under fasted and fed state conditions

Although older people are the main users of oral medications, few studies are reported on the influence of advanced age on gastric emptying rate of non-caloric liquids. This study aimed at evaluating the gastric emptying of 240 ml water in healthy older and young adults in fasted and fed state conditions using the established method of salivary caffeine kinetics. The gastric emptying of water was evaluated in 12 healthy older volunteers (mean age: 73 ± 6 years) and 12 healthy younger volunteers (mean age: 25 ± 2 years) with the ingestion of a rapid disintegrating tablet containing 20 mg of 13C3-caffeine. The gastric emptying of water was assessed indirectly by calculating the AUC ratios of salivary caffeine concentrations in specific time segments. Comparison of the AUC ratios showed no statistically significant difference between young and older volunteers in both fasted and fed state conditions (p > 0.05). Advanced age itself seems to have no relevant effect on gastric emptying of water in either fasted or fed state conditions and the phenomenon of Magenstrasse appears to follow a similar pattern in healthy older adults as in healthy younger adults.

Enteric-Coated Capsules Providing Reliable Site-Specific Drug Delivery to the Distal Ileum

Nefecon, a targeted-release capsule formulation of budesonide approved for the reduction of proteinuria in adults with primary immunoglobulin A nephropathy, targets overproduction of galactose-deficient immunoglobulin A type 1 in the Peyer's patches at the gut mucosal level. To investigate whether the commercial formulation of Nefecon capsules reliably releases budesonide to the distal ileum, a human study was conducted with test capsules reproducing the delayed-release function of Nefecon capsules. Caffeine was included in the test capsules as a marker for capsule opening in the gut since it appears rapidly in saliva after release from orally administered dosage forms. Magnetic resonance imaging with black iron oxide was used to determine the capsule's position in the gut at the time caffeine was first measured in saliva and additionally to directly visualize dispersion of the capsule contents in the gut. In vitro dissolution results confirmed that the test capsules had the same delayed-release characteristics as Nefecon capsules. In 10 of 12 human volunteers, the capsule was demonstrated to open in the distal ileum; in the other two subjects, it opened just past the ileocecal junction. These results compared favorably with the high degree of variability seen in other published imaging studies of delayed-release formulations targeting the gut. The test capsules were shown to reliably deliver their contents to the distal ileum, the region with the highest concentration of Peyer's patches.

Medicinal products with pH-dependent solubility-A problem for BA/BE assessment?

The ICH M13A draft bioequivalence guideline allows the exclusion of very low plasma profiles from the statistical evaluation in exceptional cases, i.e., if such phenomenon occurs due to non-compliance of subjects (not swallowing the product). Moreover, the draft ICH guideline requests additional bioequivalence studies for medicinal products with pH-dependent solubility after concomitant administration of gastric pH modifying preparations, e.g., proton pump inhibitors. Both regulations are scientifically sound, however, would need further specification. Main problem in this context is that compounds with very low solubility and slow intrinsic dissolution in the intestinal environment will cause significant bioavailability problems if their solid oral dosage forms are emptied from the stomach undisintegrated. Also, very low plasma profiles may result under these circumstances. Such cases can occur accidentally and are not resultant of non-compliance. Thus, limitation for one case per study only as suggested in the guideline is not justified.

Use of Magnetic Resonance Imaging for Visualization of Oral Dosage Forms in the Human Stomach: A Scoping Review

Oral dosage forms are the most widely and frequently used formulations to deliver active pharmaceutical ingredients (APIs), due to their ease of administration and noninvasiveness. Knowledge of intragastric release rates and gastric mixing is crucial for predicting the API release profile, especially for immediate release formulations. However, knowledge of the intragastric fate of oral dosage forms in vivo to date is limited, particularly for dosage forms administered when the stomach is in the fed state. An improved understanding of gastric food processing, dosage form location, disintegration times, and food effects is essential for greater understanding for effective API formulation design. In vitro standard and controlled modeling has played a significant role in predicting the behavior of dosage forms in vivo. However, discrepancies are reported between in vitro and in vivo disintegration times, with these discrepancies being greatest in the fed state. Studying the fate of a dosage form in vivo is a challenging process, usually requiring the use of invasive methods, such as intubation. Noninvasive, whole body imaging techniques can however provide unique insights into this process. A scoping review was performed systematically to identify and critically appraise published studies using MRI to visualize oral solid dosage forms in vivo in healthy human subjects. The review identifies that so far, an all-purpose robust contrast agent or dosage form type has not been established for dosage form visualization and disintegration studies in the gastrointestinal system. Opportunities have been identified for future studies, with particular focus on characterizing dosage form disintegration for development after the consumption food, as exemplified by the standard Food and Drug Administration (FDA) high fat meal.

Determination of Gastric Water Emptying in Fasted and Fed State Conditions Using a Compression-Coated Tablet and Salivary Caffeine Kinetics

Because of the importance of gastric emptying for pharmacokinetics, numerous methods have been developed for its determination. One of the methods is the salivary tracer technique, which utilizes an ice capsule containing caffeine as a salivary tracer. Despite the ice capsule's advantage in labeling ingested fluids with caffeine for subsequent salivary detection, its risk of premature melting before swallowing, and its complicated storage and preparation, limit its application, particularly in special populations (e.g., older people). For this reason, here, a compression-coated tablet was developed and validated against the ice capsule in a cross-over clinical trial. The two dosage forms were administered simultaneously to 12 volunteers in an upright position under fasted and fed state conditions. To distinguish the caffeine concentrations in saliva from each dosage form, regular type of caffeine (12C) was added to the tablet, while for the ice capsule 13C3 labelled caffeine was used. The salivary caffeine concentrations showed no statistically significant differences for the pharmacokinetic parameters tmax and AUC0→60 (p > 0.05). Thus, the new formulation is a useful tool for determining gastric emptying that can also be used in special populations.

In Vivo Evaluation of a Gastro-Resistant Enprotect® Capsule under Postprandial Conditions

Ready-to-fill enteric hard capsule shells are an evolving field of oral drug and nutraceutical products. Lonza Capsugel® Enprotect® capsules were recently proven to provide reliable release in the small intestine after fasted intake, but robustness against postprandial intake needed to be proven. In this study, the capsules were administered to 16 healthy young subjects after intake of a light meal. The Enprotect® capsules were labelled with 5 mg black iron oxide and 25 mg 13C3-caffeine. Magnetic Resonance Imaging was used to identify the localization and visual dispersion of the capsule filling. The salivary appearance of caffeine was considered a second independent and sensitive marker for the initial release. Whereas the fasted gastric residence time of the capsules amounted to 43 ± 32 min, it was increased to 158 ± 36 min after postprandial intake. Therefore, the mean dispersion time according to MRI and the mean caffeine appearance time were increased to 196 ± 37 min and 189 ± 37 min, respectively. But, similar to fasted administration, no capsule disintegration or leakage was observed in the stomach and 38% of the capsules disintegrated in the jejunum and 62% in the ileum. The mean dispersion time after gastric emptying and the mean caffeine appearance time after gastric emptying amounted to 38 ± 21 min and 31 ± 17 min, respectively. Both did not relevantly change compared to the fasted intake. Only the absolute dispersion time and caffeine appearance were prolonged due to the increased gastric residence and no relevant influence of the light meal was observed on the disintegration or release behavior of Enprotect® capsules after gastric emptying. The capsules also showed robust enteric properties after postprandial administration.

Viability of Lactobacillus acidophilus in Thin-Film Freeze-Dried Powders Filled in Delayed-Release Vegetarian Capsules in a Simulated Gastric Fluid

Previously, we have shown that thin-film freeze-drying can be applied to prepare dry powders of bacteria such as Lactobacillus acidophilus. Herein, we tested the viability of L. acidophilus in thin-film freeze-dried powders (TFF powders) filled in delayed-release vegetarian capsules in a simulated gastric fluid (SGF) consisting of 0.1N hydrochloric acid and sodium chloride. Initially, we determined the water removal rate from frozen thin films on relatively larger scales (i.e., 10-750 g). We then prepared and characterized two TFF powders of L. acidophilus with either sucrose and maltodextrin or sucrose and hydroxypropyl methylcellulose acetate succinate (HPMC-AS), a pH-sensitive polymer, as excipients and evaluated the viability of the bacteria after the TFF powders were filled in delayed-release vegetarian capsules and the capsules were incubated in the SGF for 30 min. On 10-750 g scales and at the settings specified, water removal from frozen thin films was faster than from slow shelf-frozen bulk solids. When the L. acidophilus in sucrose and HPMC-AS TFF powder was filled into a delayed-release capsule that was placed into another delayed-release capsule, the bacterial viability reduction after incubation in the SGF can be minimized to within 1 log in colony forming unit (CFU). However, for the L. acidophilus in sucrose and maltodextrin TFF powder, even in the capsule-in-capsule dosage form, bacterial CFU reduction was > 2 logs. TFF powders of live microorganisms containing an acid-resistant material in capsule-in-capsule delayed-release vegetarian capsules have the potential for oral delivery of those microorganisms.

In Vitro and In Vivo Evaluation of Carbopol 71G NF-Based Mucoadhesive Minitablets as a Gastroretentive Dosage Form

Gastroretentive dosage forms are intended to stay inside the stomach for a long period of time while releasing an active pharmaceutical ingredient. Such systems may offer significant benefits for numerous drugs compared to other sustained release systems, such as improved pharmacokinetics/bioavailability and reduced intake frequency and thereby improved adherence to the medical therapy. However, there is no gastroretentive product on the market with proven reliable gastroretentive properties in humans. A major obstacle is the motility pattern of the stomach in the fasting state in humans, which reliably ensures gastric emptying of even large indigestible objects into the small intestine. One promising approach to avoid gastric emptying is adhesion of the drug delivery system to the gastric mucosa. In order to achieve mucoadhesive properties, minitablets containing Carbopol 71G NF were developed and compared to minitablets without adhesive properties. In a specialized mucoadhesive test system, the adhesion time was prolonged for adhesive minitablets (240 min) compared to non-adhesive minitablets (30 min). The in vivo transit behavior was investigated using magnetic resonance imaging in 11 healthy volunteers in fasted state in a crossover setup. It was found that the gastric residence time (GRT) of the adhesive minitablets (median of 37.5 min with IQR = 22.5-52.5) was statistically significantly prolonged compared to the non-adhesive minitablets (median of 7.5 with IQR = 7.5-22.5), indicating a delay in gastric emptying by adhesion to the gastric mucosa. However, the system needs further improvement to create a clinical benefit. Furthermore, it was observed that for 9 of 22 administrations (three minitablets were given simultaneously with every administration), the minitablets were not emptied together but showed different GRTs.

Comparing Salivary Caffeine Kinetics of 13C and 12C Caffeine for Gastric Emptying of 50 mL Water

Gastric water emptying as a critical parameter for oral drug absorption can be investigated by several imaging techniques or by the interpretation of pharmacokinetics of appropriate substances. Recently introduced salivary caffeine kinetics is a valuable tool, but the required caffeine abstinence limits its applicability. To avoid the caffeine abstinence, stable isotope-labeled caffeine might be used, but the representability and transferability of kinetics for evaluation of gastric emptying must be demonstrated. Thus, salivary caffeine pharmacokinetics were compared for naturally occurring ¹²C-caffeine and ¹³C₃-caffeine after the administration of water under fasting conditions in six healthy young subjects. For this purpose, an ice capsule containing the two caffeine species was administered with 50 mL tap water. Gastric water emptying was simultaneously quantified using magnetic resonance imaging (MRI). Gastric emptying of 50 mL of water could be successfully evaluated. The salivary caffeine kinetics of ¹³C₃- and ¹²C-caffeine were nearly congruent and showed good linear correlations in all subjects, with a mean correlation coefficient of 0.96 in pooled data. Thus, the substitution of natural ¹²C caffeine with stable isotope-labeled ¹³C₃-caffeine offers the opportunity for broader application of the salivary caffeine gastric emptying technique and increases the robustness of the method against environmental contamination with caffeine.

In vitro evaluation of the gastrointestinal delivery of acid-sensitive pancrelipase in a next generation enteric capsule using an exocrine pancreatic insufficiency disease model

The dissolution characteristics of five capsules (Next Generation Enteric [NGE], Vcaps® Enteric [VCE], VCE DUOCAP® [VCE/VCE] system, Hard Gelatin Capsule [HGC] as negative control, and Creon® 10,000 U as market reference) were evaluated using an in vitro simulation of the stomach and upper intestinal tract with an acidic duodenal incubation (pH 4.5 for the first 10 min, pH 6 for the remaining 17 min) to simulate exocrine pancreatic insufficiency. Caffeine was a marker of capsule dissolution, and tributyrin to butyrate conversion measured pancrelipase activity. All capsules were filled with pancrelipase; the NGE, VCE, VCE/VCE, and HGC capsules also contained 50 mg caffeine. Caffeine was released first from the HGC capsule, followed by the VCE, NGE, and VCE/VCE capsules. Pancrelipase activity followed this trend and demonstrated a similar activity level over time for the NGE, VCE/VCE, and Creon® capsules. The HGC formulation confirmed gastric degradation of unprotected pancrelipase. NGE capsules provided similar protection to the simple fill formulation as observed for the complex formulation of the Creon® capsule in a setting with increased pepsin activity and may hasten the time needed to go from formula development to first-in-human studies for pH sensitive drugs or those requiring small intestine targeting.

Commercially Available Enteric Empty Hard Capsules, Production Technology and Application

Currently, there is a growing need to prepare small batches of enteric capsules for individual therapy or clinical evaluation since many acidic-sensitive substances should be protected from the stomach's acidic environment, including probiotics or fecal material, in the fecal microbiota transplantation (FMT) process. A suitable method seems to be the encapsulation of drugs or lyophilized alternatively frozen biological suspensions in commercial hard enteric capsules prepared by so-called Enteric Capsule Drug Delivery Technology (ECDDT). Manufacturers supply these types of capsules, made from pH-soluble polymers, in products such as AR Caps®, EnTRinsicTM, and Vcaps® Enteric, or capsules made of gelling polymers that release their content as the gel erodes over time when passing through the digestive tract. These include DRcaps®, EMBO CAPS® AP, BioVXR®, or ACGcaps™ HD. Although not all capsules in all formulations meet pharmaceutical requirements for delayed-release dosage forms in disintegration and dissolution tests, they usually find practical application. This literature review presents their composition and properties. Since ECDDT is a new technology, this article is based on a limited number of references.

In Vivo Evaluation of a Gastro-Resistant HPMC-Based “Next Generation Enteric” Capsule

Many orally dosed APIs are bioavailable only when formulated as an enteric dosage form to protect them from the harsh environment of the stomach. However, an enteric formulation is often accompanied with a higher development effort in the first place and the potential degradation of fragile APIs during the coating process. Ready-to-use enteric hard capsules would be an easily available alternative to test and develop APIs in enteric formulations, while decreasing the time and cost of process development. In this regard, Lonza Capsugel® Next Generation Enteric capsules offer a promising approach as functional capsules. The in vivo performance of these capsules was observed with two independent techniques (MRI and caffeine in saliva) in eight human volunteers. No disintegration or content release in the stomach was observed, even after highly variable individual gastric residence times (range 7.5 to 82.5 min), indicating the reliable enteric properties of these capsules. Seven capsules disintegrated in the distal part of the small intestine; one capsule showed an uncommonly fast intestinal transit (15 min) and disintegrated in the colon. The results for this latter capsule by MRI and caffeine appearance differed dramatically, whereas for all other capsules disintegrating in the small intestine, the results were very comparable, which highlights the necessity for reliable and complementary measurement methods. No correlation could be found between the gastric residence time and disintegration after gastric emptying, which confirms the robust enteric formulation of those capsules.

Drug-Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!

Imaging techniques such as Raman spectroscopy, electron microscopy, laser scanning confocal microscopy, atomic force microscopy, tomography, magnetic resonance imaging, and terahertz are powerful tools to elucidate drug-release mechanisms from different types of delivery devices [...]