Novel Biphasic In Vitro Dissolution Method Correctly Predicts the Oral Bioavailability of Curcumin in Humans.

In vitro dissolution methods correctly predicting in vivo bioavailability of compounds from complex mixtures are lacking. We therefore used data on the in vivo performance of bioavailability-improved curcumin formulations to implement an in vivo predictive dissolution method (BiPHa+). BiPHa+ was applied for the characterization of eight curcumin formulations previously studied in a strictly controlled pharmacokinetic human trial. During dissolution, the dissolved proportion of curcumin in the aqueous medium underwent a formulation-dependent reduction, whereas the proportion remained stable in the organic layer. Compared with conventional dissolution systems, BiPHa+ was superior in terms of in vivo-relevant formulation characterization. All formulations could be precisely categorized according to their bioavailability in humans. In vitro-in vivo relationships for each dissolution method were established, with BiPHa+ providing the highest degree of linearity (r2 = 0.9975). The BiPHa+ assay correctly predicted the bioavailability of curcuminoids from complex mixtures and provided mechanistic information about formulation-dependent release characteristics.

Advanced In Vivo Prediction by Introducing Biphasic Dissolution Data into PBPK Models.

Coupling biorelevant in vitro dissolution with in silico physiological-based pharmacokinetic (PBPK) tools represents a promising method to describe and predict the in vivo performance of drug candidates in formulation development including non-passive transport, prodrug activation, and first-pass metabolism. The objective of the present study was to assess the predictability of human pharmacokinetics by using biphasic dissolution results obtained with the previously established BiPHa+ assay and PBPK tools. For six commercial drug products, formulated by different enabling technologies, the respective organic partitioning profiles were processed with two PBPK in silico modeling tools, namely PK-Sim and GastroPlus®, similar to extended-release dissolution profiles. Thus, a mechanistic dissolution/precipitation model of the assessed drug products was not required. The developed elimination/distribution models were used to simulate the pharmacokinetics of the evaluated drug products and compared with available human data. In essence, an in vitro to in vivo extrapolation (IVIVE) was successfully developed. Organic partitioning profiles obtained from the BiPHa+ dissolution analysis enabled highly accurate predictions of the pharmacokinetic behavior of the investigated drug products. In addition, PBPK models of (pro-)drugs with pronounced first-pass metabolism enabled adjustment of the solely passive diffusion predicting organic partitioning profiles, and increased prediction accuracy further.

Novel biopharmaceutical development investigations towards drug and formulation performance optimization

For a drug to excerpt pharmacological action after oral intake, it first needs to be released from the formulation, get into solution (dissolve), be absorbed, and reach the systemic circulation. Since only solubilized drugs can be absorbed, and thus have therapeutic effect, the understanding of the dissolution and drug release processes of a drug product is of primary importance. Such understanding allows a robust formulation development with an ideal in vivo performance. In order to meet set standards, the performance assessment of oral drug products, such as dissolution testing, often applies conditions that are not reflective of the in vivo environment. The use of non-physiologically relevant dissolution method during the drug product development phase can be misleading and give poor mechanistic understanding of the in vivo dissolution process. Hence, we hypothesized that applying physiologically relevant conditions to the dissolution test would result in more accurate in vivo predictability for a robust and precise development process. Since the buffering system in the intestinal lumen operates at low molarity values, phosphate buffer at low buffer capacity was used as a first approach to an in vivo relevant parameter. Furthermore, a biphasic system was used, that is, the low buffer capacity medium was paired with an organic layer (n-octanol) to mimic the concurrent drug absorption that happens with the in vivo dissolution. Both poorly and highly soluble drugs in immediate release formulations (ibuprofen and metronidazole, respectively) were tested in this set-up to assess the dissolution in the aqueous medium and the partitioning to the organic phase. Additionally, enteric coated formulations were tested in bicarbonate buffer at the in vivo reported molarities values to assess the impact of buffer species on drug dissolution. The evaluated parameters were the buffer system (bicarbonate buffer vs. phosphate buffer), buffer capacity and medium pH. In all approaches, dissolution was also carried out in compendial buffer for comparison purposes. Our results demonstrate that the USP-recommended dissolution method greatly lacked discriminatory power, whereas low buffer capacity media discriminated between manufacturing methods. The use of an absorptive phase in the biphasic dissolution test assisted in controlling the medium pH due to the drug removal from the aqueous medium. Hence, the applied noncompendial methods were more discriminative to drug formulation differences and manufacturing methods than conventional dissolution conditions. In this study, it was demonstrated how biphasic dissolution and a low buffer capacity can be used to assess drug product performance differences. This can be a valuable approach during the early stages of drug product development for investigating drug release with improved physiological relevance. Similarly, all the enteric coated formulations displayed a fast release in phosphate buffer and complied with the compendial performance specifications. On the other hand, they all had a much slower drug release in bicarbonate buffer and failed the USP acceptance criteria. Also, the nature of the drug (acid vs base) impacted the dissolution behavior in bicarbonate buffer. This study indicates that compendial dissolution test for enteric coated tablets lacks physiological relevance and it needs to be reevaluated. Thus, an in vivo relevant performance method for EC products is needed. Overall, the findings of this thesis comprehensively demonstrates that meaningful differences in performance and accordance to clinical reports were only obtained when physiological relevant conditions were applied. Hence, our results indicate that the central hypothesis was answered positively

Para que um medicamento exerça a ação farmacológica após a ingestão oral, ele primeiro precisa ser liberado da formulação, dissolver, ser absorvido e atingir a circulação sistêmica. Uma vez que apenas medicamentos solubilizados podem ser absorvidos e, assim, ter efeito terapêutico, a compreensão dos processos de dissolução e liberação de um medicamento é de extrema importância. Tal compreensão permite o desenvolvimento de uma formulação robusta com o desempenho in vivo ideal. Para atender aos padrões regulatórios previamente estabelecidos, a avaliação da performance de formulações orais, como por exemplo, o teste de dissolução, frequentemente aplica condições que não refletem o ambiente fisiológico. O uso de métodos de dissolução não fisiologicamente relevante durante a fase de desenvolvimento do medicamento pode gerar resultados equivocados sem uma compreensão mecanistica do processo de dissolução in vivo. Portanto, a hipótese desse trabalho é que a aplicação de condições fisiologicamente relevantes no teste de dissolução resultaria em uma predição mais precisa da dissolução in vivo para um processo de desenvolvimento robusto e preciso. Uma vez que o sistema tampão no lúmen intestinal possui baixa molaridade, o tampão fosfato com baixa capacidade tamponante foi usado como uma primeira abordagem como um meio de dissolução fisiologicamente relevante. Além disso, foi utilizado um sistema bifásico, ou seja, o meio de baixa capacidade tamponante combinado a uma fase orgânica (n-octanol) para imitar a absorção in vivo. Formulações de liberação imediata contendo fármacos de baixa e de alta solubilidade (ibuprofeno e metronidazol, respectivamente) foram testadas no sistema bifásico para avaliar a dissolução no meio aquoso e a partição para a fase orgânica. Ademais, formulações com revestimento entérico foram testadas em tampão bicarbonato nos valores de molaridades fisiológicos para avaliar o impacto da espécie tamponante na dissolução do fármaco. Os parâmetros avaliados foram o sistema tampão (tampão bicarbonato vs. tampão fosfato), capacidade tamponante e pH médio. Em todas as abordagens, a dissolução também foi realizada em tampão farmacopeico para fins de comparação. Nossos resultados demonstraram que o método de dissolução farmacopeico não foi discriminativo, enquanto o meio com menor capacidade tamponante diferenciou entre as formulações obtidas via granulação úmida ou compressão direta. Ademais, a utilização da fase orgânica no teste de dissolução bifásica auxiliou no controle do pH do meio aquoso. Portanto, os métodos não compendiais aplicados foram mais discriminativos do que as condições de dissolução convencionais. Neste estudo, foi demonstrado como a dissolução bifásica e uma baixa capacidade tamponante podem ser usadas para avaliar as diferenças na performance de formulações. Esta pode ser uma abordagem valiosa durante os estágios iniciais do desenvolvimento de medicamentos para investigar a liberação destes sob condições fisiologicamente relevantes. Da mesma forma, todas as formulações com revestimento entérico exibiram uma liberação rápida em tampão de fosfato e atenderam às especificações farmacopeicas. Entretanto, a liberação do fármaco foi muito mais lenta em tampão de bicarbonato e consequentemente não cumpriram com as especificações farmacopeicas. Além disso, a natureza do fármaco (ácido vs. base) impactou o comportamento de dissolução no tampão de bicarbonato. Este estudo indica que o teste de dissolução convencional para comprimidos de liberação retardada não possui relevância fisiológica e precisa ser reavaliado. Portanto, os resultados desta tese demonstram de forma abrangente que diferenças significativas na performance condizentes com relatórios clínicos foram obtidas apenas quando as condições fisiológicas relevantes foram aplicadas. Esses resultados indicam que a hipótese central foi respondida positivamente

In vitro and in vivo assessment of hydroxypropyl cellulose as functional additive for enabling formulations containing itraconazole.

Using polymers as additives to formulate ternary amorphous solid dispersions (ASDs) has successfully been established to increase the bioavailability of poorly soluble drugs, when one polymer is not able to provide both, stabilizing the drug in the matrix and the supersaturated solution. Therefore, we investigated the influence of low-viscosity hydroxypropyl cellulose (HPC) polymers as an additive in HPMC based ternary ASD formulations made by hot-melt extrusion (HME) on the bioavailability of itraconazole (ITZ). The partitioning potential of the different HPC grades was screened in biphasic supersaturation assays. Solid-state analytics were performed using differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD). The addition of HPCs, especially HPC-UL, resulted in a superior partitioned amount of ITZ in biphasic supersaturation assays. Moreover, the approach in using HPCs as an additive in HPMC based ASDs led to an increase in partitioned ITZ compared to Sporanox® in biorelevant biphasic dissolution studies. The results from the biphasic dissolution experiments correlated well with the in vivo studies, which revealed the highest oral bioavailability for the ternary ASD comprising HPC-UL and HPMC.

The relevance of supersaturation and solubilization in the gastrointestinal tract for oral bioavailability: An in vitro vs. in vivo approach.

The influence of supersaturation and solubilization on oral absorption was assessed independently from the dissolution process for the non-formulated model drugs celecoxib and telmisartan. In vitro, physicochemical characterization and biphasic dissolution were used to characterize the supersaturation and solubilization effects of three water soluble polymers (copovidone, methylcellulose and Soluplus®) on the drugs. While celecoxib precipitated in a crystalline form resulting in pronounced stabilization of supersaturation, telmisartan precipitated as a highly energetic amorphous form and the potential of the polymers to enhance its solubility was subsequently, limited. In vivo, for the crystalline precipitating celecoxib, supersaturation and solubilization increased its oral bioavailability up to 10-fold. On the contrary, the amorphous precipitating telmisartan did not benefit from the limited stabilization in terms of oral exposure. Amongst all investigated in vitro tests the biphasic dissolution test was the most predictive in relation to supersaturation. However, for the potential micellar solubilization and the respective impact in the aqueous/organic interface, prediction accuracy of the biphasic dissolution test was limited in combination with Soluplus®. Despite the hetergeneous micellar distribution in vitro and permeation in vivo, the biphasic approach could clearly show the supersaturation potential on bioavailability (BA) for celecoxib on the one hand and the inferiority of supersaturation on BA for telmisartan.

Shared IVIVR for Five Commercial Enabling Formulations Using the BiPHa+ Biphasic Dissolution Assay.

The present study intended to confirm the in vivo relevance of the BiPHa+ biphasic dissolution assay using a single set of assay parameters. Herein, we evaluated five commercial drug products formulated by various enabling formulation principles under fasted conditions using the BiPHa+ assay. The in vitro partitioning profiles in the organic phase were compared with human pharmacokinetic data obtained from literature. In the first part, a meaningful in vitro dose of the formulations was assessed by determining the maximum drug concentration in the artificial absorption sink during dissolution (organic 1-decanol layer, Cdec,max). Then, the maximum concentration of the partitioned drug in the organic layer was correlated with the in vivo fraction absorbed, which was derived from published human pharmacokinetic data. Fraction absorbed represents the percentage, which is absorbed from the intestine without considering first pass. It was found that the maximum drug concentration in the organic phase obtained from an in vitro dose of ten milligrams, which is equivalent to 15-25 µmol of the respective drug, led to the highest congruency with the fraction absorbed in vivo. In the second part, the in vivo relevance of the BiPHa+ dissolution data was verified by establishing a shared in vitro/in vivo relationship including all formulations. Based on the in vitro kinetics of the BiPHa+ experiments human in vivo plasma profiles were predicted using convolutional modelling approach. Subsequently, the calculated pharmacokinetic profiles were compared with in vivo performance of the studied drug products to assess the predictive power of the BiPHa+ assay. The BiPHa+ assay demonstrated biorelevance for the investigated in vitro partitioning profiles using a single set of assay parameters, which was verified based on human pharmacokinetic data of the five drug products.

Biphasic dissolution test and its application in the evaluation of poorly soluble drug preparations / 药学学报

Biphasic dissolution test, consisting of immiscible aqueous and organic phase, is an in vitro dissolution method that simultaneously measures the dissolution and partition of drugs. Due to the advantages of simulating in vivo absorption and overcoming the influence of surfactants on dissolution, it has been widely used to evaluate the poorly soluble drugs in vitro dissolution. Based on the relevant research in this field in recent years, this review summarizes the history, dissolution device, theoretical model and application of the biphasic dissolution test. Finally, the prospects in the development of biphasic dissolution test are also outlined.

Solubility and Stability Enhanced Oral Formulations for the Anti-Infective Corallopyronin A.

Novel-antibiotics are urgently needed to combat an increase in morbidity and mortality due to resistant bacteria. The preclinical candidate corallopyronin A (CorA) is a potent antibiotic against Gram-positive and some Gram-negative pathogens for which a solid oral formulation was needed for further preclinical testing of the active pharmaceutical ingredient (API). The neat API CorA is poorly water-soluble and instable at room temperature, both crucial characteristics to be addressed and overcome for use as an oral antibiotic. Therefore, amorphous solid dispersion (ASD) was chosen as formulation principle. The formulations were prepared by spray-drying, comprising the water-soluble polymers povidone and copovidone. Stability (high-performance liquid chromatography, Fourier-transform-infrared spectroscopy, differential scanning calorimetry), dissolution (biphasic dissolution), and solubility (biphasic dissolution, Pion's T3 apparatus) properties were analyzed. Pharmacokinetic evaluations after intravenous and oral administration were conducted in BALB/c mice. The results demonstrated that the ASD formulation principle is a suitable stability- and solubility-enhancing oral formulation strategy for the API CorA to be used in preclinical and clinical trials and as a potential market product.

Novel Biphasic Lipolysis Method To Predict in Vivo Performance of Lipid-Based Formulations.

The absence of an intestinal absorption sink is a significant weakness of standard in vitro lipolysis methods, potentially leading to poor prediction of in vivo performance and an overestimation of drug precipitation. In addition, the majority of the described lipolysis methods only attempt to simulate intestinal conditions, thus overlooking any supersaturation or precipitation of ionizable drugs as they transition from the acidic gastric environment to the more neutral conditions of the intestine. The aim of this study was to develop a novel lipolysis method incorporating a two-stage gastric-to-intestinal transition and an absorptive compartment to reliably predict in vivo performance of lipid-based formulations (LBFs). Drug absorption was mimicked by in situ quantification of drug partitioning into a decanol layer. The method was used to characterize LBFs from four studies described in the literature, involving three model drugs (i.e., nilotinib, fenofibrate, and danazol) where in vivo bioavailability data have previously been reported. The results from the novel biphasic lipolysis method were compared to those of the standard pH-stat method in terms of reliability for predicting the in vivo performance. For three of the studies, the novel biphasic lipolysis method more reliably predicted the in vivo bioavailability compared to the standard pH-stat method. In contrast, the standard pH-stat method was found to produce more predictive results for one study involving a series of LBFs composed of the soybean oil, glyceryl monolinoleate (Maisine CC), Kolliphor EL, and ethanol. This result was surprising and could reflect that increasing concentrations of ethanol (as a cosolvent) in the formulations may have resulted in greater partitioning of the drug into the decanol absorptive compartment. In addition to the improved predictivity for most of the investigated systems, this biphasic lipolysis method also uses in situ analysis and avoids time- and resource-intensive sample analysis steps, thereby facilitating a higher throughput capacity and biorelevant approach for characterization of LBFs.

Biphasic Dissolution as an Exploratory Method During Early Drug Product Development.

Dissolution testing is a major tool used to assess a drug product's performance and as a quality control test for solid oral dosage forms. However, compendial equipment and methods may lack discriminatory power and the ability to simulate aspects of in vivo dissolution. Using low buffer capacity media combined with an absorptive phase (biphasic dissolution) increases the physiologic relevance of in vitro testing. The purpose of this study was to use non-compendial and compendial dissolution test conditions to evaluate the in vitro performance of different formulations. The United States Pharmacopeia (USP)-recommended dissolution method greatly lacked discriminatory power, whereas low buffer capacity media discriminated between manufacturing methods. The use of an absorptive phase in the biphasic dissolution test assisted in controlling the medium pH due to the drug removal from the aqueous medium. Hence, the applied non-compendial methods were more discriminative to drug formulation differences and manufacturing methods than conventional dissolution conditions. In this study, it was demonstrated how biphasic dissolution and a low buffer capacity can be used to assess in vitro drug product performance differences. This can be a valuable approach during the early stages of drug product development for investigating in vitro drug release with improved physiological relevance.

On the Usefulness of Two Small-Scale In Vitro Setups in the Evaluation of Luminal Precipitation of Lipophilic Weak Bases in Early Formulation Development.

A small-scale biphasic dissolution setup and a small-scale dissolution-permeation (D-P) setup were evaluated for their usefulness in simulating the luminal precipitation of three lipophilic weak bases-dipyridamole, ketoconazole and itraconazole. The transition from the gastric to intestinal environment was incorporated into both experimental procedures. Emulsification during the biphasic dissolution experiments had a minimal impact on the data, when appropriate risk mitigation steps were incorporated. Precipitation parameters estimated from the in vitro data were inputted into the Simcyp® physiologically based pharmacokinetic (PBPK) modelling software and simulated human plasma profiles were compared with previously published pharmacokinetic data. Average Cmax and AUC values estimated using experimentally derived precipitation parameters from the biphasic experiments deviated from corresponding published actual values less than values estimated using the default simulator parameters for precipitation. The slow rate of transport through the biomimetic membrane in the D-P setup limited its usefulness in forecasting the rates of in vivo precipitation used in the modelling of average plasma profiles.

A Rational Design of a Biphasic DissolutionSetup-Modelling of Biorelevant Kinetics for a Ritonavir Hot-Melt Extruded Amorphous Solid Dispersion.

Biphasic dissolution systems achieved good predictability for the in vivo performance of several formulations of poorly water-soluble drugs by characterizing dissolution, precipitation, re-dissolution, and absorption. To achieve a high degree of predictive performance, acceptor media, aqueous phase composition, and the apparatus type have to be carefully selected. Hence, a combination of 1-decanol and an optimized buffer system are proposed as a new, one-vessel biphasic dissolution method (BiPHa+). The BiPHa+ was developed to combine the advantages of the well-described biorelevance of the United States Pharmacopeia (USP) apparatus II coupled with USP apparatus IV and a small-scale, one-vessel method. The BiPHa+ was designed for automated medium addition and pH control of the aqueous phase. In combination with the diode array UV-spectrophotometer, the system was able to determine the aqueous and the organic medium simultaneously, even if scattering or overlapping of spectra occurred. At controlled hydrodynamic conditions, the relative absorption area, the ratio between the organic and aqueous phase, and the selected drug concentrations were identified to be the discriminating factors. The performance of a hot-melt extruded ritonavir-containing amorphous solid dispersion (ritonavir-ASD) was compared in fasted-state dissolution media leading to different dissolution-partitioning profiles depending on the content of bile salts. An advanced kinetic model for ASD-based well described all phenomena from dispersing of the ASD to the partitioning of the dissolved ritonavir into the organic phase.

Biphasic drug release testing coupled with diffusing wave spectroscopy for mechanistic understanding of solid dispersion performance.

Amorphous solid dispersions (ASDs) represent an important formulation technique to achieve supersaturation in gastrointestinal fluids and to enhance absorption of poorly water-soluble drugs. Drug release from such systems is complex due to emergence of different colloidal structures and potential drug precipitation, which can occur in parallel to absorption. The latter drug uptake from the intestinal lumen can be simulated by an organic layer in a biphasic in vitro test, which was employed in this work to mechanistically study the release of ketoconazole from ASDs produced by hot melt extrusion using different HPMCAS grades. A particular aim was to introduce diffusing wave spectroscopy (DWS) to biopharmaceutical testing of solid dispersions. Results indicated that amorphous formulations prevented crystallization of the weakly basic drug upon transfer into the intestinal medium. Microrheological differences among polymer grades and plasticizers were revealed in the aqueous phase, which affected drug release and subsequently uptake into the organic layer. The results indicate that DWS can be employed as a new non-invasive tool to better understand drug release from solid dispersions. This novel light scattering technique is highly promising for future biopharmaceutical research on supersaturating systems such as solid dispersions.

Mechanistic study on hydrodynamics in the mini-scale biphasic dissolution model and its influence on in vitro dissolution and partitioning.

Biphasic dissolution models were proposed to provide good predictive power for in vivo absorption kinetics. However, up to date the impact of hydrodynamics in mini-scale models are not well understood. Consequently, the aim of this work was to investigate different setups of a previously published mini-scale biphasic dissolution model (miBIdi-pH-II) to better understand the relevance of hydrodynamics for evaluating kinetic parameters and to simultaneously increase the robustness of the experimental model. As a first step, the hydrodynamics within the aqueous phase were characterized by in silico simulations of the flow patterns. Different settings, such as higher rotation speeds of the paddles, the implementation of a second propeller into the aqueous phase, and different shapes of aqueous stirrers were investigated. Second, to evaluate the results of the in silico simulations, in vitro experiments with glitter were carried out. Last, the same settings were applied in the miBIdi-pH-II using dipyridamole (DPD) as model compound to estimate kinetic parameters by applying a compartment-based modelling approach. Both in vitro experiments with glitter or DPD demonstrated the adequateness of the previous in silico hydrodynamic simulations. The use of higher rotation speeds and a second aqueous propeller resulted in more homogeneous mixing of the aqueous phase. This resulted in faster distribution of dissolved active pharmaceutical ingredient (API) into the octanol phase. A kinetic model was successfully applied to quantify the influence of hydrodynamics on the partitioning rate of the API into the octanol phase. In conclusion, the combination of in silico and in vitro methods was demonstrated to be powerful for investigating the flow patterns within the miBIdi-pH-II. A comprehensive understanding of the hydrodynamics and the respective influence on the dissolution and apparent partitioning into the octanol phase in the biphasic dissolution model was obtained and completed by using a compartmental kinetic model. This model allowed successful quantification of how the hydrodynamics influence the partitioning of API into the octanol phase.

Evaluation of a biphasic in vitro dissolution test for estimating the bioavailability of carbamazepine polymorphic forms.

The purpose of this study was to discriminate three crystal forms of carbamazepine (a BCS II drug) by in vitro dissolution testing and to correlate in vitro data with published in vivo data. A biphasic dissolution system (phosphate buffer pH6.8 and octanol) was used to evaluate the dissolution of the three polymorphic forms and to compare it with conventional single phase dissolution tests performed under sink and non-sink conditions. Similar dissolution profiles of three polymorphic forms were observed in the conventional dissolution test under sink conditions. Although a difference in dissolution was seen in the single phase dissolution test under non-sink conditions as well as in the aqueous phase of the biphasic test, little relevance for in vivo data was observed. In contrast, the biphasic dissolution system could discriminate between the different polymorphic forms in the octanol phase with a ranking of form III>form I>dihydrate form. This was in agreement with the in vivo performance. The dissolved drug available for oral absorption, which was dominated by dissolution and solution-mediated phase transformation, could be reflected in the biphasic dissolution test. Moreover, a good correlation was established between in vitro dissolution in the octanol phase of the biphasic test and in vivo pharmacokinetic data (R2=0.99). The biphasic dissolution method is a valuable tool to discriminate between different crystal forms in the formulations of poorly soluble drugs.

Development of a discriminative biphasic in vitro dissolution test and correlation with in vivo pharmacokinetic studies for differently formulated racecadotril granules.

The purpose of this study was to discriminate the release behavior from three differently formulated racecadotril (BCS II) granules and to establish an in vitro-in vivo correlation. Three granule formulations of the lipophilic drug were prepared with equivalent composition but prepared with different manufacturing processes (dry granulation, wet granulation with or without binder). In vitro release of the three granules was investigated using a biphasic dissolution system (phosphate buffer pH6.8 and octanol) and compared to the conventional single phase USP II dissolution test performed under sink and non-sink conditions. In vivo studies with each granule formulation were performed in rats. Interestingly, the granule formulations exhibited pronouncedly different behavior in the different dissolution systems depending on different wetting and dissolution conditions. Single phase USP II dissolution tests lacked discrimination. In contrast, remarkable discrimination between the granule formulations was observed in the octanol phase of biphasic dissolution system with a rank order of release from granules prepared by wet granulation with binder>wet granulation without binder>dry granulation. This release order correlated well with the wettability of these granules. An excellent correlation was also established between in vitro release in the octanol phase of the biphasic test and in vivo data (R2=0.999). Compared to conventional dissolution methods, the biphasic method provides great potential to discriminate between only minor formulation and process changes within the same dosage form for poorly soluble drugs.

Bioavailability enhancement of itraconazole-based solid dispersions produced by hot melt extrusion in the framework of the Three Rs rule.

Solid dispersion formulations made of itraconazole (ITZ) and Soluplus® (polyethylene glycol, polyvinyl acetate and polyvinylcaprolactame-based graft copolymer abbreviated SOL) were produced using hot melt extrusion. Since ITZ possesses a water solubility of less than 1ng/mL, the aim of this work was to enhance the aqueous solubility of ITZ, and thereby improve its bioavailability. The three formulations consisted of a simple SOL/ITZ amorphous solid dispersion (ASD), an optimized SOL/ITZ/AcDiSol® (super-disintegrant) ASD and an equimolar inclusion complex of ITZ in hydroxypropyl-ß-cyclodextrin (substitution degree=0.63, CD) with SOL. The three formulations were compared in vitro and in vivo to the marketed product Sporanox®. The in vitro enhancement of dissolution rate was evaluated using a biphasic dissolution test. In vitro dissolution results showed that all three formulations had a higher percentage of ITZ released than Sporanox® with the following ranking: SOL/ITZ/CD>SOL/ITZ/AcDiSol®>SOL/ITZ>Sporanox®. The bioavailability of these four formulations was evaluated in rats. The bioanalytical method was optimized so that only 10µL of blood was withdrawn from the rats using specific volumetric absorptive microsampling devices. This enabled to keep the same rats during the whole study, which was in accordance with the Three Rs rules (reduction, refinement and replacement). Furthermore, this technique allowed the suppression of inter-individual variability. Higher Cmax and AUC were obtained after the administration of all three formulations compared to the levels after the use of Sporanox® as follows: SOL/ITZ/AcDiSol®>SOL/ITZ/CD>SOL/ITZ>Sporanox®. The inversion in the ranking between SOL/ITZ/CD and SOL/ITZ/AcDiSol® made impossible the establishment of an in vitro-vivo correlation. Indeed, very different release rates were obtained in vitro and in vivo for the two optimized formulations. These results suggest that ITZ would be protected inside the core of the SOL micelles even during the absorption step at the intestine, while some agents present in the intestinal fluids could displace ITZ from the hydrophobic cavity of CD by competition.

Evolution of a mini-scale biphasic dissolution model: Impact of model parameters on partitioning of dissolved API and modelling of in vivo-relevant kinetics.

Biphasic dissolution models are proposed to have good predictive power for the in vivo absorption. The aim of this study was to improve our previously introduced mini-scale dissolution model to mimic in vivo situations more realistically and to increase the robustness of the experimental model. Six dissolved APIs (BCS II) were tested applying the improved mini-scale biphasic dissolution model (miBIdi-pH-II). The influence of experimental model parameters including various excipients, API concentrations, dual paddle and its rotation speed was investigated. The kinetics in the biphasic model was described applying a one- and four-compartment pharmacokinetic (PK) model. The improved biphasic dissolution model was robust related to differing APIs and excipient concentrations. The dual paddle guaranteed homogenous mixing in both phases; the optimal rotation speed was 25 and 75rpm for the aqueous and the octanol phase, respectively. A one-compartment PK model adequately characterised the data of fully dissolved APIs. A four-compartment PK model best quantified dissolution, precipitation, and partitioning also of undissolved amounts due to realistic pH profiles. The improved dissolution model is a powerful tool for investigating the interplay between dissolution, precipitation and partitioning of various poorly soluble APIs (BCS II). In vivo-relevant PK parameters could be estimated applying respective PK models.

Selection of a discriminant and biorelevant in vitro dissolution test for the development of fenofibrate self-emulsifying lipid-based formulations.

Fenofibrate, a BCS class II compound, has a low bioavailability especially when taken orally on an empty stomach. The challenge to find a new formulation for providing bioavailability, independent of food, is still ongoing. If the development of a suitable oral delivery formulation of BCS class II compounds is a frequent and great challenge to formulation scientists, the in vitro evaluation of these new formulations is also a great challenge. The purpose of this study was therefore to select an in vitro dissolution test that would be useful and as biorelevant as possible for the development of fenofibrate self-emulsifying lipid-based formulations. In this context, three different fenofibrate formulations, for which in vivo data are available in the literature, were tested using different dissolution tests until we found the one that was the most suitable. As part of this approach, we started with the simplest in vitro dissolution tests and progressed to tests that were increasingly more complex. The first tests were different single phase dissolution tests: a test under sink conditions based on the USP monograph, and different tests under non-sink conditions in non-biorelevant and biorelevant media. Given the inconclusive results obtained with these tests, biphasic dissolution systems were then tested: one with USP apparatus type II alone and another which combined USP apparatus types II and IV. This last combined test seemed the most suitable in vitro dissolution test for the development of the future fenofibrate lipid-based formulations we intend to develop in our own laboratory.

Development of a biphasic dissolution test for Deferasirox dispersible tablets and its application in establishing an in vitro-in vivo correlation.

In a biphasic dissolution medium, the integration of the in vitro dissolution of a drug in an aqueous phase and its subsequent partitioning into an organic phase is hypothesized to simulate the in vivo drug absorption. Such a methodology is expected to improve the probability of achieving a successful in vitro-in vivo correlation. Dissolution of Dispersible tablets of Deferasirox, a biopharmaceutics classification system type II compound, was studied in a biphasic dissolution medium using a flow-through dissolution apparatus coupled to a paddle apparatus. The experimental parameters associated with dissolution were optimized to discriminate between Deferasirox dispersible tablets of different formulations. The dissolution profiles obtained from this system were subsequently used to construct a level A in vitro-in vivo correlation.