Fed State Simulated Intestinal Fluid Research Articles

Characterization of Macrocyclic Peptide Drug Interactions with Bile Salts and Biorelevant Colloids via Single Amino Acid Mutations and 1H Nuclear Magnetic Resonance (NMR) Spectroscopy

There is growing interest in the oral delivery of poorly permeable peptide drugs; however, the effect of biorelevant colloids found in the aqueous gastrointestinal environment on peptide drug solution behavior has been largely understudied. In this work, we detail the molecular level interactions between octreotide, a water-soluble macrocyclic peptide drug, and biorelevant colloids, i.e. bile salt micelles and bile salt-phospholipid mixed micelles, via dialysis membrane flux experiments and proton nuclear magnetic resonance (1H NMR) spectroscopy. A modified alanine scan was employed to generate eight mutated octreotide analogs; the impact of individual amino acid mutations on peptide dialysis membrane flux rates in micellar (trihydroxy and dihydroxy) bile salt solutions as well as fasted state simulated intestinal fluid (FaSSIF) and fed state simulated intestinal fluid (FeSSIF) was evaluated and compared against the parent peptide, octreotide. We show that octreotide interacts more strongly with dihydroxy bile salt micelles than trihydroxy bile salt micelles in solution, and in FaSSIF/FeSSIF media, octreotide mainly interacts with the phospholipid component. These interactions are largely mediated by hydrophobic interactions of octreotide's aromatic residues as well as electrostatic interactions between octreotide's basic Lys residue and terminal amine.

Head-to-Head Comparison of Caco-2 Transwell and Gut-on-a-Chip Models for Assessing Oral Peptide Formulations.

Oral delivery of potent peptide drugs provides key formulation challenges in the pharmaceutical industry: stability, solubility, and permeability. Intestinal permeation enhancers (PEs) can overcome the low oral bioavailability by improving the drug permeability. Conventional in vitro and ex vivo models for assessing PEs fail to predict efficacy in vivo. Here, we compared Caco-2 cells cultured in the conventional static Transwell model to a commercially available continuous flow microfluidic Gut-on-a-Chip model. We determined baseline permeability of FITC-Dextan 3 kDa (FD3) in Transwell (5.3 ± 0.8 × 10-8 cm/s) vs Chip (3.2 ± 1.8 × 10-7 cm/s). We screened the concentration impact of two established PEs sodium caprate and sucrose monolaurate and indicated a requirement for higher enhancer concentration in the Chip model to elicit equivalent efficacy e.g., 10 mM sodium caprate in Transwells vs 25 mM in Chips. Fasted and fed state simulated intestinal fluids (FaSSIF/FeSSIF) were introduced into the Chip and increased basal FD3 permeability by 3-fold and 20-fold, respectively, compared to 4-fold and 4000-fold in Transwells. We assessed the utility of this model to peptides (Insulin and Octreotide) with PEs and observed much more modest permeability enhancement in the Chip model in line with observations in ex vivo and in vivo preclinical models. These data indicate that microfluidic Chip models are well suited to bridge the gap between conventional in vitro and in vivo models.

Efficiency of single pharmaceutical surfactants to mimic intestinal biorelevant media solubilization and dissolution of etravirine: Comparison of intrinsic and film dissolution models

We understand that quality control dissolution media may best anticipate in vivo product performance by mimicking in vivo media, but preferably involve at most a single pharmaceutical surfactant for routine laboratory use. The objective here was to estimate the concentrations of six pharmaceutical surfactants to mimic etravirine solubility and intrinsic dissolution rate, as well as dissolution rate from a film model, in each Fed State Simulated Intestinal Fluid Version 2 (FeSSIF-V2) and Fasted State Simulated Intestinal Fluid Version 2 (FaSSIF-V2). Solubility studies and colloid sizing measurements were conducted. Results indicate that all six surfactants were more efficient than FeSSIF-V2 or FaSSIF-V2 at solubilizing drug, and also exhibited higher micelle diffusivities than FeSSIF-V2 and FaSSIF-V2 mixed-micelles. The rank-order potency (on mM basis) of the six pharmaceutical surfactants to mimic etravirine solubility in each FeSSIF-V2 and FaSSIF-V2 was: polysorbate 80 (PS80) > polysorbate 20 (PS20) > polyoxyethylene(23) lauryl ether (POE23) > POE10 > hexadecyltrimethylammonium bromide (HEX) > sodium lauryl sulfate (SLS). This rank-order potency was almost the same to mimic drug dissolution rate into each FeSSIF-V2 and FaSSIF-V2, except POE10 > POE23. For the most potent surfactant, PS80, 0.461 mM and 0.140 mM PS80 was estimated to mimic etravirine's solubility and dissolution rate into FeSSIF-V2, respectively, using the intrinsic dissolution model. The low PS80 concentration to mimic dissolution rate reflects the relatively high diffusivity of PS80 micelles, compared to FeSSIF-V2 mixed-micelle diffusivity, which was the case for all six pharmaceutical surfactants. Results are also presented in terms of a film dissolution model for surfactant-mediated dissolution, where dissolution enhancement was less than that in the intrinsic dissolution model, and the film model required lower surfactant concentration than in intrinsic dissolution model to mimic FeSSIF-V2-enhanced dissolution. Findings have promised to identify single pharmaceutical surfactant concentrations that mimic key performance attributes of biorelevant media.

Importance of Considering Fed-State Gastrointestinal Physiology in Predicting the Reabsorption of Enterohepatic Circulation of Drugs

PurposeThe purpose of this study was to develop a simulation model for the pharmacokinetics (PK) of drugs undergoing enterohepatic circulation (EHC) with consideration to the environment in the gastrointestinal tract in the fed state in humans. The investigation particularly focused on the necessity of compensating for the permeability rate constant in the reabsorption process in consideration of drug entrapment in bile micelles.MethodsMeloxicam and ezetimibe were used as model drugs. The extent of the entrapment of drugs inside bile micelles was evaluated using the solubility ratio of Fed State Simulated Intestinal Fluid version 2 (FeSSIF-V2) to Fasted State Simulated Intestinal Fluid version 2 (FaSSIF-V2). Prediction accuracy was evaluated using the Mean Absolute Percentage Error (MAPE) value, calculated from the observed and predicted oral PK profiles.ResultsThe solubilization of ezetimibe by bile micelles was clearly observed while that of meloxicam was not. Assuming that only drugs in the free fraction of micelles permeate through the intestinal membrane, PK simulation for ezetimibe was performed in both scenarios with and without compensation by the permeation rate constant. The MAPE value of Zetia® tablet, containing ezetimibe, was lower with compensation than without compensation. By contrast, Mobic® tablet, containing meloxicam, showed a relatively low MAPE value even without compensation.ConclusionFor drugs which undergo EHC and can be solubilized by bile micelles, compensating for the permeation rate constant in the reabsorption process based on the free fraction ratio appears an important factor in increasing the accuracy of PK profile prediction.

Green Tea Catechins Decrease Solubility of Raloxifene In Vitro and Its Systemic Exposure in Mice.

Green tea is a widely consumed beverage. A recent clinical study reported green tea decreased systemic exposure of raloxifene and its glucuronide metabolites by 34-43%. However, the underlying mechanism(s) remains unknown. This study investigated a change in raloxifene's solubility as the responsible mechanism. The effects of green tea extract, (-)-epigallocatechin gallate (EGCG), and (-)-epigallocatechin (EGC) on raloxifene's solubility were assessed in fasted state simulated intestinal fluids (FaSSIF) and fed state simulated intestinal fluids (FeSSIF). EGCG and EGC represent green tea's main bioactive constituents, flavan-3-gallate and flavan-3-ol catechins respectively, and the tested concentrations (mM) match the µg/mg of each compound in the extract. Our mouse study (n = 5/time point) evaluated the effect of green tea extract and EGCG on the systemic exposure of raloxifene. EGCG (1mM) and EGC (1.27mM) decreased raloxifene's solubility in FaSSIF by 78% and 13%, respectively. Micelle size in FaSSIF increased with increasing EGCG concentrations (> 1000% at 1mM), whereas EGC (1.27mM) did not change micelle size. We observed 3.4-fold higher raloxifene solubility in FeSSIF compared to FaSSIF, and neither green tea extract nor EGCG significantly affected raloxifene solubility or micelle size in FeSSIF. The mice study showed that green tea extract significantly decreased raloxifene Cmax by 44%, whereas EGCG had no effect. Green tea extract and EGCG did not affect the AUC0-24h of raloxifene or the metabolite-to-parent AUC ratio. This study demonstrated flavan-3-gallate catechins may decrease solubility of poorly water-soluble drugs such as raloxifene, particularly in the fasted state.

Impact of prandial state on luminal and permeation-behavior of fosamprenavir oral suspension studied by in vitro tools: Solubility-, bioconversion- and permeation- studies in biomimetic media

Fosamprenavir is a prodrug designed to overcome the solubility challenge of the parent drug amprenavir, a protease inhibitor. For the marketed oral suspension (Telzir®) a clinically documented negative food effect has been reported.The present study aims to gain a better mechanistic understanding of the food effect by in vitro tests on solubility, bioconversion, permeability, and dynamic dissolution/bioconversion/permeation studies in a high throughput manner on a microtiter plate (Permeapad® Plate). In order to mimick luminal condition changes in connection with food, various modified versions of fasted and fed state simulated intestinal fluids (FaSSIF-V2) and (FeSSIF–V2) were used. The kinetics of enzymatic cleavage (simulated bioconversion) were studied in these media with a focus on molecularly dissolved drug concentrations using microdialysis. Dynamic dissolution/bioconversion/permeation experiments, indicated the following factors to contribute to reduced permeation in fed state: elevated inorganic phosphate concentrations, higher concentrations of bile salts and lipids and lower intestinal pH. The impact of these effects is difficult to capture in vivo due to their interconnection and large variability between individuals.This study revealed factors leading to an altered luminal behavior of Telzir® oral suspension in fed state, which may contribute to explain the observed reduced amprenavir absorption from the suspension. Especially the high throughput small-scale dissolution/bioconversion/permeation experiments on a microtiter plate were demonstrated an efficient and powerful tool for elucidating the food effects of phosphate-ester prodrug type drug products as far as their altered luminal behavior is concerned.

Optimization, cellular uptake, and in vivo evaluation of Eudragit S100-coated bile salt-containing liposomes for oral colonic delivery of 5-aminosalicylic acid

Eudragit S100-coated bile salt-containing liposomes were prepared and optimized by experimenting with different variables, including bile salt type and concentration, and the method of incorporation into liposomes using a model hydrophilic compound, 5-aminosalicylic acid (5-ASA). After optimizing the formulation, cellular uptake, and animal pharmacokinetic experiments were performed. The inclusion of sodium glycocholate (SG) into liposomes decreased liposome particle size and entrapment efficiency significantly but had no effect on zeta potential. The method of incorporating SG into the lipid or aqueous phase of the liposome did not notably impact the characteristics of the liposomes but the hydration media had a substantial effect on the entrapment efficiency of 5-ASA. In vitro drug release in different fluids simulating distinct gastrointestinal tract sections, indicated pH-dependent disintegration of the coating layer of coated SG-containing liposomes. The majority of the drug was retained when subjected to simulated gastric fluid (SGF) and fed-state simulated intestinal fluid (FeSSIF) (≈ 37% release after 2 h in SGF pH 1.2, followed by 3 h in FeSSIF pH 5). The remaining drug was subsequently released in phosphate-buffered saline pH 7.4 (≈ 85% release within 24 h). Increasing SG concentration in the liposomes decreased the amount of drug released in FeSSIF. Similar results were observed when SG was replaced with sodium taurocholate. Cellular uptake studies in Caco-2 cells demonstrated that all liposomal formulations (conventional liposomes, bile salt-containing liposomes, and coated bile salt-containing liposomes) have shown to be equally effective at increasing the cellular uptake compared to free fluorescein solution. In the pharmacokinetic study, coated bile salt-containing liposomes showed a lower Cmax and prolonged residence in the gastrointestinal tract in comparison to conventional liposomes. Taken together, these findings suggest that the polymer-coated bile salt-containing liposomes have the potential to serve as a drug delivery system targeted at the colon.

Food and bile micelle binding of quaternary ammonium compounds.

Physiologically-based biopharmaceutics modeling (PBBM) has been widely used to predict the oral absorption of drugs. However, the prediction of food effects on oral drug absorption is still challenging, especially for negative food effects. Marked negative food effects have been reported in most cases of quaternary ammonium compounds (QAC). However, the mechanism has remained unclear. The purpose of the present study was to investigate the bile micelle and food binding of QACs as a mechanism of the negative food effect. Trospium (TRS), propantheline (PPT), and ambenonium (AMB) were selected as model QAC drugs. The oral absorption of these QACs has been reported to be reduced by 77% (TRS), > 66% (PPT), and 79% (AMB), when taken with food. The fasted and fed state simulated intestinal fluids (FaSSIF and FeSSIF, containing 3 and 15 mM taurocholic acid, respectively) with or without FDA breakfast homogenate (BFH) were used as the simulated intestinal fluid. The unbound fraction (fu) of the QACs in these media was measured by dynamic dialysis. The fu ratios (FeSSIF/ FaSSIF) were 0.67 (TRS), 0.47 (PPT), and 0.76 (AMB). When BFH was added to FeSSIF, it was reduced to 0.39 (TRS), 0.28 (PPT), and 0.59 (AMB). These results suggested that bile micelle and food binding play an important role in the negative food effect on the oral absorption of QACs.

Co-Dispersion Delivery Systems with Solubilizing Carriers Improving the Solubility and Permeability of Cannabinoids (Cannabidiol, Cannabidiolic Acid, and Cannabichromene) from Cannabis sativa (Henola Variety) Inflorescences.

Cannabinoids: cannabidiol (CBD), cannabidiolic acid (CBDA), and cannabichromene (CBC) are lipophilic compounds with limited water solubility, resulting in challenges related to their bioavailability and therapeutic efficacy upon oral administration. To overcome these limitations, we developed co-dispersion cannabinoid delivery systems with the biopolymer polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol (Soluplus) and magnesium aluminometasilicate (Neusilin US2) to improve solubility and permeability. Recognizing the potential therapeutic benefits arising from the entourage effect, we decided to work with an extract instead of isolated cannabinoids. Cannabis sativa inflorescences (Henola variety) with a confirming neuroprotective activity were subjected to dynamic supercritical CO2 (scCO2) extraction and next they were combined with carriers (1:1 mass ratio) to prepare the co-dispersion cannabinoid delivery systems (HiE). In vitro dissolution studies were conducted to evaluate the solubility of CBD, CBDA, and CBC in various media (pH 1.2, 6.8, fasted, and fed state simulated intestinal fluid). The HiE-Soluplus delivery systems consistently demonstrated the highest dissolution rate of cannabinoids. Additionally, HiE-Soluplus exhibited the highest permeability coefficients for cannabinoids in gastrointestinal tract conditions than it was during the permeability studies using model PAMPA GIT. All three cannabinoids exhibited promising blood-brain barrier (BBB) permeability (Papp higher than 4.0 × 10-6 cm/s), suggesting their potential to effectively cross into the central nervous system. The improved solubility and permeability of cannabinoids from the HiE-Soluplus delivery system hold promise for enhancement in their bioavailability.

Structural Investigation on How Guest Loading of Poly(2-oxazoline)-Based Micelles Affects the Interaction with Simulated Intestinal Fluids.

Drug loading of polymer micelles can have a profound effect on their particle size and morphology as well as their physicochemical properties. In turn, this influences performance in biological environments. For oral delivery of drugs, the intestinal environment is key, and consequently, a thorough structural understanding of what happens at this material-biology interface is required to understand in vivo performance and tailor improved delivery vehicles. In this study, we address this interface in vitro through a detailed structural characterization of the colloidal assemblies of polymeric micelles based on poly(2-oxazolines) with three different guest loadings with the natural product curcumin (17-52 wt %) in fed-state simulated intestinal fluids (FeSSIF). For this, we employ NMR spectroscopy, in particular, 1H NMR, 1H-1H-NOESY, and 1H DOSY experiments complemented by quantum chemical calculations and cryo-TEM measurements. Through this mixture of methods, we identified curcumin-taurocholate interactions as central interaction patterns alongside interactions with the polymer and lipids. Furthermore, curcumin molecules can be exchanged between polymer micelles and bile colloids, an important prerequisite for their uptake. Finally, increased loading of the polymer micelles with curcumin resulted in a larger number of vesicles as taurocholate─through coordination with Cur─is less available to form nanoparticles with the lipids. The loading-dependent behavior found in this study deviates from previous work on a different drug substance highlighting the need for further studies including different drug molecules and polymer types to improve the understanding of events on the molecular level.

Indigestible Dextrin Alleviates the Intestinal Absorption of Alpha-linolenic Acid More Markedly Than That of Linoleic Acid in Obese Mice

Linoleic acid (LA) and alpha-linolenic acid (ALA) constitute the main dietary polyunsaturated fatty acids. Indigestible dextrin (DEX) is a dietary fiber that causes a beneficial decrease in lifestyle-related disease risk factors. We investigated the effects of DEX on intestinal absorption of LA and ALA in obese mice. KK-Ay/TaJcl obese mice were fed an ALA- or LA-abundant diet and provided with water in the absence and presence of 0.06 w/v% DEX for 4 weeks. The levels of lipids in serum samples and the lipase activity in serum and liver were analyzed. The effects of DEX on the intestinal absorption of LA and ALA were investigated using an in vitro model of the intestinal absorption process in the fed-state simulated intestinal fluid (FeSSIF) solution. ALA resulted in an increase in the serum triglyceride (TG) levels than those observed upon feeding an LA-abundant diet. DEX suppressed significantly the ALA-dependent increase in serum TG levels. Neither LA nor ALA affected the serum levels of total cholesterol and high-density lipoprotein cholesterol, as well as the serum and hepatic lipase activities. Moreover, ALA showed better solubility than LA in FeSSIF solution. The solubility of ALA in FeSSIF solution was significantly suppressed by DEX, whereas that of LA was not affected by DEX. ALA can be absorbed more easily than LA during the intestinal absorption process, probably leading to an increase in the serum TG levels and then DEX more selectively inhibits the intestinal absorption of ALA compared to that of LA.

Characterization of neonatal and infant enterostomy fluids - part II: Drug solubility

Previous research revealed marked differences in the composition of intestinal fluids between infants and adults. To explore the impact on the solubilization of orally administered drugs, the present study assessed the solubility of five poorly water-soluble, lipophilic drugs in intestinal fluid pools from 19 infant enterostomy patients (infant HIF). For some but not all drugs, the average solubilizing capacity of infant HIF was similar to that of HIF obtained from adults (adult HIF) in fed conditions. Commonly used fed state simulated intestinal fluids (FeSSIF(-V2)) predicted fairly well drug solubility in the aqueous fraction of infant HIF, but did not account for the substantial solubilization by the lipid phase of infant HIF. Despite similarities in the average solubilities of some drugs in infant HIF and adult HIF or SIF, the underlying solubilization mechanisms likely differ, considering important compositional differences (e.g., low bile salt levels). Finally, the huge variability in composition of infant HIF pools resulted in a highly variable solubilizing capacity, potentially causing variations in drug bioavailability. The current study warrants future research focusing on (i) understanding the mechanisms underlying drug solubilization in infant HIF and (ii) evaluating the sensitivity of oral drug products to interpatient variations in drug solubilization.

The impact of viscosity on the dissolution of naproxen immediate-release tablets

ObjectivesThe increase in viscosity of gastric fluid as a result of food ingestion is one criterion that can negatively impact the dissolution and solubility of orally administered medications. Consequently, it is crucial to address this issue in the pharmacokinetic profile assessment of oral formulations. In this scientific work, various kinds of viscosity enhancers, namely carboxy methylcellulose, pectin, guar gum, and xanthan, were applied to the preparation of different media similar to the biological condition after a meal, and their impacts on the rate of naproxen dissolution and its saturation solubility were evaluated. MethodsA Brookfield viscometer was used to assess the rheological features of two potencies of each viscosity booster dissolved in fed state simulated intestinal fluid (FeSSIF). After 24 h of samples shaking, the saturation solubility of the selected medicine in the assessed media was measured using an ultraviolet spectrophotometer, and investigation of the drug dissolution profile was performed with a paddle dissolution apparatus in 200 mL of fluid. ResultsGreat reduction in the saturation solubility of naproxen was detected when the viscosity of the tested media was increased and the highest reduction of solubility was observed with pectin in FeSSIF. Similarly, the dissolution profile of naproxen decrease with enhancement of the viscosity of investigated media. ConclusionA polymer structure not only enhances the viscosity of media but also interferes with drug solubilization. As a result, it is essential to address the rheological aspect in designing in vitro media during the assessment of drug dissolution profiles.

Ritonavir nanosuspensions prepared by microfluidization with enhanced solubility and desirable immunological properties

The objective of this study was to develop ritonavir (RTV) nanosuspensions (NSs) by microfluidization method. Particle size (PS) measurements were performed by photon correlation spectroscopy. Amorphous properties of the particles were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dissolution studies were conducted in fed state simulated intestinal fluid (FeSSIF) medium. The flow cytometry was utilized to determine the lymphocyte sub-groups and immune response of NSs. RTV NSs were obtained with 400–500 nm PS. The crystal properties of RTV remain unchanged. The solubility of NS was enhanced five times. 57% and 18% of RTV were dissolved in FeSSIF medium for NSs and coarse powder. According to immunological studies, the prepared NSs did not significantly alter the ratio of CD4+/CD8+. Therefore, NSs may be a beneficial approach for the oral administration of RTV.

Survival of human coronavirus 229E at different temperatures on various food-contact surfaces and food and under simulated digestive conditions

The COVID-19 pandemic caused by SARS-CoV-2 has had a major impact on human health and the global economy. Various transmission possibilities of SARS-CoV-2 have been proposed, such as the surface of food in the cold chain and food packaging, as well as the fecal-oral route, although person-to-person contact via droplets and aerosols has been confirmed as the main route of transmission. This study evaluated the survivability of HCoV-229E, a SARS-CoV-2 surrogate, in suspension, on food-contact surfaces and on food at various temperatures, and in simulated digestive fluids by TCID50 assay. In suspension, HCoV-229E survived after 5 days at 20 °C with a 3.69 log reduction, after 28 days at 4 °C with a 3.07 log reduction, and after 12 weeks at –20 °C with a 1.18 log reduction. On food-contact surfaces, HCoV-229E was not detected on day 3 on stainless steel (SS), plastic (LDPE), and silicone rubber (SR) at 20 °C with a 3.28, 3.24 and 3.28 log reduction, respectively, and survived after 28 days on SS and LDPE at 4 °C with a 3.13 and 2.88 log reduction, respectively, and survived after 12 weeks on SS, LDPE, and SR at –20 °C with a 1.92, 1.32 and 1.99 log reduction, respectively. On food, HCoV-229E was not detected on day 3 on lettuce and day 4 on chicken breast and salmon at 20 °C with a 3.61, 3.26 and 3.08 log reduction, respectively, and on day 14 on lettuce and day 21 on chicken breast and salmon at 4 °C with a 3.88, 3.44 and 3.56 log reduction, respectively. The virus remained viable for 12 weeks in all foods at –20 °C with 2–2.47 log reduction. In addition, in simulated digestive fluid experiments, HCoV-229E was relatively resistant in simulated salivary fluid (SSF; pH 7, 5), fed state simulated gastric fluid (FeSSGF; pH 3, 5, 7), and fasted state simulated intestinal fluid (FaSSIF; pH 7). However, the virus was less tolerant in fasted state simulated gastric fluid (FaSSGF; pH 1.6) and fed state simulated intestinal fluid (FeSSIF; pH 5). Therefore, this study suggested that HCoV-229E remained infectious on various food-contact surfaces and foods; in particular, it survived longer at lower temperatures and survived depending on the pH of the simulated digestive fluid.

Mechanistic analysis for positive and negative food effects on oral absorption of poorly soluble drugs from cyclodextrin containing formulations: Study with a mini-scale in vitro system

The aim of this study is to understand the basic mechanism of the food effect on oral drug absorption from cyclodextrin (CyD) containing formulations. Danazol (DNZ) and Albendazole (ABZ) were used as model drugs with poor water solubility. Both drugs were suspended or dissolved in Fasted State or Fed State Simulated Intestinal Fluid (FaSSIF or FeSSIF) containing various concentrations of 2-Hydroxypropyl-beta-cyclodextrin (HP-βCyD). Drugs were applied to a μFlux system as a suspension or solution and the dissolved concentration and the permeated amount were monitored. Dissolved drug concentration was analyzed based on the chemical equilibrium to calculate the concentrations of free drug, drug-CyD complex and drug-bile acid micelle complex. Mathematical analysis revealed that the bile acid also interacted with HP-βCyD to displace the drug and reduced the solubilizing capacity of HP-βCyD. The permeation rate of DNZ was faster in FaSSIF than in FeSSIF at 1% HP-βCyD while it became faster in FeSSIF at 2% HP-βCyD, suggesting that complexes with HP-βCyD and with the bile acid micelle can diffuse through the unstirred water layer to contribute to the permeation by providing a free DNZ at the vicinity of the membrane. In contrast, the permeation of ABZ follows the free drug concentration since its permeation is rate-limited by the membrane permeation itself. In vivo rat study with 1% HP-βCyD showed the higher absorption of DNZ in FaSSIF than in FeSSIF, corresponding well to the in vitro results. With 2% HP-βCyD, almost the same absorption profiles were observed in FaSSIF and FeSSIF despite the faster membrane permeation in FeSSIF, possibly due to the slower dissolution of DNZ in FeSSIF. In conclusion, in vitro study with a mini-scale system such as a μFlux system is useful to understand the complicated interactions of the drug with CyDs and/or bile acids and is helpful for designing efficient and robust formulations of poorly soluble drugs using CyDs as an excipient.

Food effect risk assessment in preformulation stage using material sparing μFLUX methodology.

The intake of food and meal type can strongly impact the bioavailability of orally administered drugs and can consequently impact drug efficacy and safety. During the early stages of drug development, only a small amount of drug substance is available, and the solubility difference between fasted state simulated intestinal fluid and fed state simulated intestinal fluid may provide an early indication about the probable food effect. But higher drug solubility in fed state simulated intestinal fluid may not always results in an increased oral absorption. In the present research, we demonstrated using 11 model compounds that in addition to the drug dissolution in biorelevant media, the evaluation of the diffusion flux of a drug in solution, across artificial lipid coated membrane, where only the unbound drug crosses the membrane, is a reliable way to predict the food effect. Although, the combination of dissolution and diffusion flux may not reliably predict the food effect in case of drugs undergoing intestinal metabolism or when transporters are involved in the drug absorption, the technique generally provides good information about the food effect at very early stages of drug development that may help in designing a clinical plan by adjusting the drug dose in the fed state.

Explicit-pH Coarse-Grained Molecular Dynamics Simulations Enable Insights into Restructuring of Intestinal Colloidal Aggregates with Permeation Enhancers

Permeation enhancers (PEs) can increase the bioavailability of drugs. The mechanisms of action of these PEs are complex, but, typically, when used for oral administration, they can transiently induce the alteration of trans- and paracellular pathways, including increased solubilization and membrane fluidity, or the opening of the tight junctions. To elucidate these mechanistic details, it is important to understand the aggregation behavior of not only the PEs themselves but also other molecules already present in the intestine. Aggregation processes depend critically on, among other factors, the charge state of ionizable chemical groups, which is affected by the pH of the system. In this study, we used explicit-pH coarse-grained molecular dynamics simulations to investigate the aggregation behavior and pH dependence of two commonly used PEs—caprate and SNAC—together with other components of fasted- and fed-state simulated intestinal fluids. We also present and validate a coarse-grained molecular topology for the bile salt taurocholate suitable for the Martini3 force-field. Our results indicate an increase in the number of free molecules as a function of the system pH and for each combination of FaSSIF/FeSSIF and PEs. In addition, there are differences between caprate and SNAC, which are rationalized based on their different molecular structures and critical micelle concentrations.

Impact of Swelling of Spray Dried Dispersions in Dissolution Media on their Dissolution: An Investigation Based on UV Imaging

Impact of SDD-dissolution medium interactions on the swelling and dissolution of spray dried dispersions (SDDs) was investigated using UV imaging by monitoring SDD swelling in situ, along with correlating of the swelling with the micro-dissolution and intrinsic dissolution of SDDs. SDDs of ketoconazole or indomethacin with three polymers: polyvinylpyrrolidone (PVP), hydroxypropyl cellulose (HPC), and hydroxypropyl methylcellulose acetate succinate (HPMC-AS) were prepared for the study. Dissolution media employed for assessing swelling and dissolution include water, acetate buffer, phosphate buffer, fasted state simulated intestinal fluid (FaSSIF), and fed state simulated intestinal fluid (FeSSIF), in which influence of polymers and drugs together with the physical-chemical properties of dissolution media (pH, and the presence of sodium taurocholate and lecithin) on SDD swelling and dissolution was evaluated. It appears that hydrophilic and hydrophobic properties of polymers can significantly impact SDD swelling and thus the dissolution. Furthermore, properties of dissolution media such as pH as well as presence of bile salts and lecithin seems to affect SDD swelling and dissolution as well. Throughout the text, thermodynamic swelling of polymers was used to interpret SDD dissolution behavior. Finally, practical implication of polymer swelling on dissolution was discussed.

Dissolution/Permeation of Albendazole in the Presence of Cyclodextrin and Bile Salts: A Mechanistic In Vitro Study into Factors Governing Oral Bioavailability

We aimed to understand the impact of the interplay between bile salts and cyclodextrins on the dissolution-permeation of poorly soluble drug compounds with a moderate-strong binding constant to cyclodextrin. Phase diagrams were prepared on the chosen model compound albendazole in phosphate buffer, fasted state simulated intestinal fluid (FaSSIF), and a modified fed state simulated intestinal fluid (FeSSIFmod) with (2-hydroxypropyl)-beta-cyclodextrin (HP-β-CD) concentrations of up to 10 % (m/m). Then we investigated the dissolution/permeation interplay of albendazole dissolved/suspended in the different media through a biomimetic barrier on a 96-well in vitro model. The apparent solubility of albendazole was enhanced by HP-β-CD and FaSSIF/FeSSIFmod separately. However, when albendazole was dissolved in HP-β-CD and biomimetic media together, the solubility was significantly lower than the predicted additive solubility from the solubilizing effects. It is postulated that this is due to the sodium taurocholate from the biomimetic media displacing albendazole from the hydrophobic cavity of HP-β-CD. In the permeation experiments, the highest permeation was observed at cyclodextrin concentrations able to solubilize close to the total dose of albendazole without a major surplus of solubilization capacity. Furthermore, an over-proportional permeation enhancement was observed when both, cyclodextrin and biomimetic media were present. These results indicate that the interplay between bile salts and cyclodextrins can enhance the free (molecularly dissolved) fraction of drug in solution to a greater extent than could be obtained with one of the solubilizing components alone. In conclusion, at carefully selected cyclodextrin-concentrations in combination with biomimetic media, obviously, a transient supersaturation is induced, which is made responsible for the observed major permeation enhancement.