The influence of gastric motility on the intraluminal behavior of fosamprenavir

The effect of sparkling water on the systemic pharmacokinetics of paracetamol in older adults

Paracetamol absorption kinetics show considerable variability in older adults, complicating the development of effective dosing regimens in the advanced-age population. In previous research, sparkling water has been shown to influence absorption-related processes. This study aimed to apply these findings to older adults and investigate the impact of sparkling water on absorption-related variability and early exposure. To this end, fourteen volunteers, with a median age of 72.5, were enrolled in a small-scale, randomised, controlled clinical trial with a cross-over design. A single immediate-release 500 mg paracetamol tablet was administered with sparkling or still water. Venous blood samples were collected regularly over 8 hours and analysed using HPLC-UV. Reduced variability of absorption-related parameters and a trend towards higher early exposure were observed in the sparkling water group, as demonstrated by a 1.6-fold increased AUC0-30min, a 2-fold reduced geometric coefficient of variation (GCV) for AUC0-30min, and a reduced median [interquartile range] Tmax of 25.0 [20.0-30.0] min compared to 30.0 [25.0-45.0] min. Based on our findings, sparkling water as a real-life dosing condition might improve paracetamol absorption kinetics and early exposure in the advanced-age population.

In Vitro Simulation of the Fasted Gastric Conditions and Their Variability to Elucidate Contrasting Properties of the Marketed Dabigatran Etexilate Pellet-Filled Capsules and Loose Pellets

Variability of the gastrointestinal tract is rarely reflected in in vitro test protocols but often turns out to be crucial for the oral dosage form performance. In this study, we present a generation method of dissolution profiles accounting for the variability of fasted gastric conditions. The workflow featured 20 biopredictive tests within the physiological variability. The experimental array was constructed with the use of the design of experiments, based on three parameters: gastric pH and timings of the intragastric stress event and gastric emptying. Then, the resulting dissolution profiles served as a training data set for the dissolution process modeling with the machine learning algorithms. This allowed us to generate individual dissolution profiles under a customizable gastric pH and motility patterns. For the first time ever, we used the method to successfully elucidate dissolution properties of two dosage forms: pellet-filled capsules and bare pellets of the marketed dabigatran etexilate product Pradaxa. We showed that the dissolution of capsules was triggered by mechanical stresses and thus was characterized by higher variability and a longer dissolution onset than observed for pellets. Hence, we proved the applicability of the method for the in vitro and in silico characterization of immediate-release dosage forms and, potentially, for the improvement of in vitro-in vivo extrapolation.

Drug Dissolution in Oral Drug Absorption: Workshop Report

The in-person workshop "Drug Dissolution in Oral Drug Absorption" was held on May 23-24, 2023, in Baltimore, MD, USA. The workshop was organized into lectures and breakout sessions. Three common topics that were re-visited by various lecturers were amorphous solid dispersions (ASDs), dissolution/permeation interplay, and in vitro methods to predict in vivo biopharmaceutics performance and risk. Topics that repeatedly surfaced across breakout sessions were the following: (1) meaning and assessment of "dissolved drug," particularly of poorly water soluble drug in colloidal environments (e.g., fed conditions, ASDs); (2) potential limitations of a test that employs sink conditions for a poorly water soluble drug; (3) non-compendial methods (e.g., two-stage or multi-stage method, dissolution/permeation methods); (4) non-compendial conditions (e.g., apex vessels, non-sink conditions); and (5) potential benefit of having both a quality control method for batch release and a biopredictive/biorelevant method for biowaiver or bridging scenarios. An identified obstacle to non-compendial methods is the uncertainty of global regulatory acceptance of such methods.

Application of biorelevant in vitro assays for the assessment and optimization of ASD-based formulations for pediatric patients

Amorphous solid dispersions (ASD) have been a successful formulation strategy to overcome the poor aqueous solubility of many novel drugs, but the development of pediatric formulations presents a special challenge due to variable gastrointestinal conditions in children. It was the aim of this work to design and apply a staged biopharmaceutical test protocol for the in vitro assessment of ASD-based pediatric formulations. Ritonavir was used as a model drug with poor aqueous solubility. Based on the commercial ASD powder formulation, a mini-tablet and a conventional tablet formulation were prepared. Drug release from the three formulations was studied in different biorelevant in vitro assays (i.e. MicroDiss, two-stage, transfer model, tiny-TIM) to consider different aspects of human GI physiology. Data from the two-stage and transfer model tests indicated that by controlled disintegration and dissolution excessive primary precipitation can be prevented. However, this advantage of the mini-tablet and tablet formulation did not translate into better performance in tiny-TIM. Here, the in vitro bioaccessibility was comparable for all three formulations. In the future, the staged biopharmaceutical action plan established herein will support the development of ASD-based pediatric formulations by improving the mechanistic understanding so that formulations are developed for which drug release is robust against variable physiological conditions.

Nanomedicine based potentially transformative strategies for colon targeting of peptides: State-of-the-art

Recently, peptides have attracted tremendous attention among researchers attributed to their high target specificity and efficacy compared to conventional therapeutics. The ease of self-administration and non-invasiveness confers oral as the most desirable route. However, numerous challenges associated with peptide delivery through the oral route like harsh gastrointestinal environment, enzymatic degradation, and absorption barriers hinder its clinical translation. Protease activity is more pronounced in the proximal segments of the gastrointestinal tract (GIT). Distal segments like the colon possess lower proteolytic activity, enhanced retention time, etc. which could facilitate easy absorption. However, traversing of the upper segments to reach the colon requires the circumvention of the pitfalls of the GIT. The advent of nanomedicine strategies could help in overcoming the said challenges associated with oral delivery, colon-specific targeting, and improving stability and bioavailability at the active site. Furthermore, the classification of peptides and various nanomedicine strategies for oral delivery of peptides to the colon has been conveyed. Regulatory hurdles and ways to accomplish clinical translation have been addressed.

Application of In Vivo Imaging Techniques and Diagnostic Tools in Oral Drug Delivery Research

Drug absorption following oral administration is determined by complex and dynamic interactions between gastrointestinal (GI) physiology, the drug, and its formulation. Since many of these interactions are not fully understood, the COST action on “Understanding Gastrointestinal Absorption-related Processes (UNGAP)” was initiated in 2017, with the aim to improve the current comprehension of intestinal drug absorption and foster future developments in this field. In this regard, in vivo techniques used for the characterization of human GI physiology and the intraluminal behavior of orally administered dosage forms in the GI tract are fundamental to gaining deeper mechanistic understanding of the interplay between human GI physiology and drug product performance. In this review, the potential applications, advantages, and limitations of the most important in vivo techniques relevant to oral biopharmaceutics are presented from the perspectives of different research fields.

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.

Insight into the Colonic Disposition of Sulindac in Humans

NSAIDs such as celecoxib and sulindac play a critical role in the treatment of colorectal cancer, yet it is not understood how sufficiently high concentrations are reached in colonic tissue. We previously demonstrated that an incomplete small intestinal absorption of celecoxib enables gut driven drug accumulation in caecal tissue, which is most likely needed for inducing remission. However, a multistage dissolution experiment suggested a more extensive absorption of sulindac relative to celecoxib, though still incomplete. To study whether caecal accumulation of sulindac is solely plasma driven or also gut driven, we performed an exploratory clinical study in healthy volunteers. After intake of a tablet of sulindac (200 mg; Arthrocine), two colonoscopies (1.0-2.5 h, and 6.0-7.5 h after drug intake) were performed to assess concentrations of sulindac and metabolites in plasma, caecal tissue and caecal contents. We observed that sulindac, even without the use of a colon-targeted delivery strategy, can arrive at the colonic lumen due to incomplete absorption and biliary excretion, and that the microbiota can catalyse the production of sulindac sulfide, which then accumulates in a high and local manner in the colonic tissue. These data can be relevant for drug development in the treatment of colorectal adenomas and cancer.

Exploring the impact of real-life dosing conditions on intraluminal and systemic concentrations of atazanavir in parallel with gastric motility recording in healthy subjects

This work strived to explore gastrointestinal (GI) dissolution, supersaturation and precipitation of the weakly basic drug atazanavir in humans under different 'real-life' intake conditions. The impact of GI pH and motility on these processes was thoroughly explored. In a cross-over study, atazanavir (Reyataz®) was orally administered to 5 healthy subjects with (i) a glass of water, (ii) a glass of Coca-Cola® and (iii) a glass of water under hypochlorhydric conditions (induced by concomitant intake of a proton-pump inhibitor (PPI)). After intake, GI fluids were aspirated from the stomach and the duodenum and, subsequently, analyzed for atazanavir. In parallel, blood samples were collected to assess systemic concentrations. In general, the results of this study revealed that the acidic gastric pH in combination with gastric residence time played a crucial role in the dissolution of atazanavir along the GI tract. After intake of atazanavir with a glass of water (i.e., reference condition), complete gastric dissolution was observed. After GI transfer, supersaturation was noticed for a limited amount of time (1.25 h). With respect to the Coca-Cola® condition, complete gastric dissolution was also observed. A delay in gastric emptying, highly likely caused by the caloric content (101 kcal), was responsible for delayed arrival of atazanavir into the upper small intestine, creating a longer time window of supersaturated concentrations in the duodenal segment (3.25 h) compared to the water condition. The longer period of supersaturated concentrations resulted in a slightly higher systemic exposure of atazanavir compared to the condition when atazanavir was taken with a glass of water. A remarkable observation was the creation (when the drug was given in the migrating motor complex (MMC) phase 2) or maintenance (when the drug was given in MMC phase 1) of a quiescent phase for up to 80 min. With respect to the PPI condition, negligible gastric and intestinal concentrations were observed, resulting in minimal systemic exposure for all subjects. It can be concluded that gastric pH and residence time play a pivotal role in the intestinal disposition of atazanavir in order to generate sufficiently high concentrations further down in the intestinal tract for a sufficient period of time, thus creating a beneficial driving force for intestinal absorption.