Topography of Simulated Intestinal Equilibrium Solubility

A novel simulated media system for in vitro evaluation of bioequivalent intestinal drug solubility

Orally administered solid drug must dissolve in the gastrointestinal tract before absorption to provide a systemic response. Intestinal solubility is therefore crucial but difficult to measure since human intestinal fluid (HIF) is challenging to obtain, varies between fasted (Fa) and fed (Fe) states and exhibits inter and intra subject variability. A single simulated intestinal fluid (SIF) cannot reflect HIF variability, therefore current approaches are not optimal. In this study we have compared literature Fa/FeHIF drug solubilities to values measured in a novel in vitro simulated nine media system for either the fasted (Fa9SIF) or fed (Fe9SIF) state. The manuscript contains 129 literature sampled human intestinal fluid equilibrium solubility values and 387 simulated intestinal fluid equilibrium solubility values. Statistical comparison does not detect a difference (Fa/Fe9SIF vs Fa/FeHIF), a novel solubility correlation window enclosed 95% of an additional literature Fa/FeHIF data set and solubility behaviour is consistent with previous physicochemical studies. The Fa/Fe9SIF system therefore represents a novel in vitro methodology for bioequivalent intestinal solubility determination. Combined with intestinal permeability this provides an improved, population based, biopharmaceutical assessment that guides formulation development and indicates the presence of food based solubility effects. This transforms predictive ability during drug discovery and development and may represent a methodology applicable to other multicomponent fluids where no single component is responsible for performance.

Structured solubility behaviour in fed simulated intestinal fluids

Intestinal drug solubility is a key parameter controlling absorption after the administration of a solid oral dosage form. The ability to measure fed state solubility in vitro is limited and multiple simulated intestinal fluid recipes have been developed but with no consensus which is optimal. This study has utilised nine bioequivalent simulated fed intestinal media recipes that cover over 90% of the compositional variability of sampled fed human intestinal fluid. The solubility of 24 drugs (Acidic; furosemide, ibuprofen, indomethacin, mefenamic acid, naproxen, phenytoin, piroxicam, valsartan, zafirlukast: Basic; aprepitant, atazanavir, bromocriptine, carvedilol, dipyridamole, posaconazole, tadalafil: Neutral; acyclovir, carbamazepine, felodipine, fenofibrate, griseofulvin, itraconazole, paracetamol, probucol) has been assessed to determine if structured solubility behaviour is present. The measured solubility behaviour can be split into four categories and is consistent with drug physicochemical properties and previous solubility studies. For acidic drugs (category 1) solubility is controlled by media pH and the lowest and highest pH media identify the lowest and highest solubility in 90% of cases. For weakly acidic, basic and neutral drugs (category 2) solubility is controlled by media pH and total amphiphile concentration (TAC), a consistent solubility pattern is evident with variation related to individual drug media component interactions. The lowest and highest pH × TAC media identify the lowest and highest solubility in 70% and 90% of cases respectively. Four drugs, which are non-ionised in the media systems (category 3), have been identified with a very narrow solubility range, indicating minimal impact of the simulated media on solubility. Three drugs exhibit solubility behaviour that is not consistent with the remainder (category 4). The results indicate that the use of two bioequivalent fed intestinal media from the original nine will identify in vitro the maximum and minimum solubility values for the majority of drugs and due to the media derivation this is probably applicable in vivo. When combined with a previous fasted study, this introduces interesting possibilities to measure a solubility range in vitro that can provide Quality by Design based decisions to rationalise drug and formulation development. Overall this indicates that the multi-dimensional media system is worthy of further investigation as in vitro tool to assess fed intestinal solubility.

Integration of Biorelevant Pediatric Dissolution Methodology into PBPK Modeling to Predict In Vivo Performance and Bioequivalence of Generic Drugs in Pediatric Populations: a Carbamazepine Case Study

This study investigated the impact of gastro-intestinal fluid volume and bile salt (BS) concentration on the dissolution of carbamazepine (CBZ) immediate release (IR) 100 mg tablets and to integrate these in vitro biorelevant dissolution profiles into physiologically based pharmacokinetic modelling (PBPK) in pediatric and adult populations to determine the biopredictive dissolution profile. Dissolution profiles of CBZ IR tablets (100 mg) were generated in 50-900 mL biorelevant adult fasted state simulated gastric and intestinal fluid (Ad-FaSSGF and Ad-FaSSIF), also in three alternative compositions of biorelevant pediatric FaSSGF and FaSSIF medias at 200 mL. This study found that CBZ dissolution was poorly sensitive to changes in the composition of the biorelevant media, where dissimilar dissolution (F2 = 46.2) was only observed when the BS concentration was changed from 3000 to 89 μM (Ad-FaSSIF vs Ped-FaSSIF 50% 14 BS). PBPK modeling demonstrated the most predictive dissolution volume and media composition to forecast the PK was 500 mL of Ad-FaSSGF/Ad-FaSSIF media for adults and 200 mL Ped-FaSSGF/FaSSIF media for pediatrics. A virtual bioequivalence simulation was conducted by using Ad-FaSSGF and/or Ad-FaSSIF 500 mL or Ped-FaSSGF and/or Ped-FaSSIF 200 mL dissolution data for CBZ 100 mg (reference and generic test) IR product. The CBZ PBPK models showed bioequivalence of the product. This study demonstrates that the integration of biorelevant dissolution data can predict the PK profile of a poorly soluble drug in both populations. Further work using more pediatric drug products is needed to verify biorelevant dissolution data to predict the in vivo performance in pediatrics.

Fed Intestinal Solubility Limits and Distributions Applied to the Developability Classification System

For solid oral dosage forms drug solubility in intestinal fluid is an important parameter influencing product performance and bioavailability. Solubility along with permeability are the two parameters applied in the Biopharmaceutics and Developability Classification Systems (DCS) to assess a drug's potential for oral administration. Intestinal solubility varies with the intestinal contents and the differences between the fasted and fed states are recognised to influence solubility and bioavailability. In this study a novel fed state simulated media system comprising of nine media has been utilised to measure the solubility of seven drugs (ibuprofen, mefenamic acid, furosemide, dipyridamole, griseofulvin, paracetamol and acyclovir) previously studied in the fasted state DCS. The results demonstrate that the fed nine media system provides a range of solubility values for each drug and solubility behaviour is consistent with published design of experiment studies conducted in either the fed or fasted state. Three drugs (griseofulvin, paracetamol and acyclovir) exhibit very narrow solubility distributions, a result that matches published behaviour in the fasted state, indicating that this property is not influenced by the concentration of simulated media components. The nine solubility values for each drug can be utilised to calculate a dose/solubility volume ratio to visualise the drug's position on the DCS grid. Due to the derivation of the nine media compositions the range and catergorisation could be considered as bioequivalent and can be combined with the data from the original fed intestinal fluid analysis to provide a population based solubility distribution. This provides further information on the drugs solubility behaviour and could be applied to quality by design formulation approaches. Comparison of the fed results in this study with similar published fasted results highlight that some differences detected match in vivo behaviour in food effect studies. This indicates that a combination of the fed and fasted systems may be a useful in vitro biopharmaceutical performance tool. However, it should be noted that the fed media recipes in this study are based on a liquid meal (Ensure Plus) and this may not be representative of alternative fed states achieved through ingestion of a solid meal. Nevertheless, this novel approach provides greater in vitro detail with respect to possible in vivo biopharmaceutical performance, an improved ability to apply risk-based approaches and the potential to investigate solubility based food effects. The system is therefore worthy of further investigation but studies will be required to expand the number of drugs measured and link the in vitro measurements to in vivo results.

Association of body mass index and intestinal (faecal) Streptococcus in adults in Xining city, China P.R

Body mass index (BMI) and gut microbiota show significant interaction, but most studies on the relationship between BMI and gut microbiota have been done in Western countries. Relationships that are also identified in other cultural backgrounds are likely to have functional importance. Hence here we explore gut microbiota in adults living in Xining city (China P.R.) and relate results to subject BMI. Analysis of bacterial 16s rRNA gene was performed on faecal samples from participants with normal-weight (n=24), overweight (n=24), obesity (n=11) and type 2 diabetes (T2D) (n=8). The results show that unweighted but not weighted Unifrac distance was significantly different when gut microbiota composition was compared between the groups. Importantly, the genus Streptococcus was remarkably decreased in both obese subjects and subjects suffering from T2D, as compared to normal-weight subjects. Accordingly, strong association was identified between the genus Streptococcus and BMI and especially Streptococcus salivarius subsp. thermophiles was a major contributor in this respect. As previous studies have shown that Streptococcus salivarius subsp. thermophiles is also negatively associated with obesity in Western cohorts, our results suggest that this species is a potential probiotic for the prevention of obesity and related disorders.

Small scale in vitro method to determine a potential bioequivalent equilibrium solubility range for fed human intestinal fluid

Intestinal drug solubility is a key parameter controlling oral absorption but varies both intra and inter individuals and between the fasted and fed states, with food intake known to alter the bioavailability of many compounds. Intestinal solubility can be measured in vitro either using sampled fed human intestinal fluid (FeHIF) or simulated fed intestinal fluid (SIF) but neither approach is optimal. FeHIF is difficult to obtain and variable, whilst for fed SIF multiple recipes are available with no consensus on the ideal version. A recent study characterised FeHIF aspirates using a multidimensional approach and calculated nine simulated media recipes that covered over ninety percent of FeHIF compositional variability. In this study the equilibrium solubility of thirteen drugs have been measured using the nine simulated media recipes and compared to multiple previous design of experiment (DoE) studies, which have examined the impact of fed SIF media components on solubility. The measured nine media solubility data set is only statistically equivalent to the large scale 92 media DoE in 4 out of 13 drug comparisons, but has improved equivalence against small scale DoEs (9 or 10 media) with 6 out of 9 or 10 out of 12 (9 and 10 media respectively) equivalent. Selective removal of non-biorelevant compositions from the 92 media DoE improves statistical equivalence to 9 out of 13 comparisons. The results indicate that solubility equivalence is linked to media component concentrations and compositions, the nine media system is measuring a similar solubility space to previous systems, with a narrower solubility range than the 92 point DoE but equivalent to smaller DoE systems. Phenytoin and tadalafil display a narrow solubility range, a behaviour consistent with previous studies in fed and fasted states and only revealed through the multiple media approach. Custom DoE analysis of the nine media results to determine the most statistically significant component influencing solubility does not detect significant components. Indicating that the approach has a low statistical resolution and is not appropriate if determination of media component significance is required. This study demonstrates that it is possible to assess the fed intestinal equilibrium solubility envelope using the nine media recipes obtained from a multi-dimensional analysis of fed HIF. The derivation of the nine media compositions coupled with the results in this study indicate that the solubility results are more likely to reflect the fed intestinal solubility envelope than previous DoE studies and highlight that the system is worthy of further investigation.

Structured solubility behaviour in bioequivalent fasted simulated intestinal fluids

Drug solubility in intestinal fluid is a key parameter controlling absorption after the administration of a solid oral dosage form. To measure solubility in vitro simulated intestinal fluids have been developed, but there are multiple recipes and the optimum is unknown. This situation creates difficulties during drug discovery and development research. A recent study characterised sampled fasted intestinal fluids using a multidimensional approach to derive nine bioequivalent fasted intestinal media that covered over 90% of the compositional variability. These media have been applied in this study to examine the equilibrium solubility of twenty one exemplar drugs (naproxen, indomethacin, phenytoin, zafirlukast, piroxicam, ibuprofen, mefenamic acid, furosemide, aprepitant, carvedilol, tadalafil, dipyridamole, posaconazole, atazanavir, fenofibrate, felodipine, griseofulvin, probucol, paracetamol, acyclovir and carbamazepine) to determine if consistent solubility behaviour was present. The bioequivalent media provide in the majority of cases structured solubility behaviour that is consistent with physicochemical properties and previous solubility studies. For the acidic drugs (pKa < 6.3) solubility is controlled by media pH, the profile is identical and consistent and the lowest and highest pH media identify the lowest and highest solubility in over 70% of cases. For weakly acidic (pKa > 8), basic and neutral drugs solubility is controlled by a combination of media pH and total amphiphile concentration (TAC), a consistent solubility behaviour is evident but with variation related to individual drug interactions within the media. The lowest and highest pH x TAC media identify the lowest and highest solubility in over 78% of cases. A subset of the latter category consisting of neutral and drugs non-ionised in the media pH range have been identified with a very narrow solubility range, indicating that the impact of the simulated intestinal media on their solubility is minimal. Two drugs probucol and atazanavir exhibit unusual behaviour. The study indicates that the use of two appropriate bioequivalent fasted intestinal media from the nine will identify in vitro the maximum and minimum solubility boundaries for drugs and due to the media derivation this is probably applicable in vivo. These media could be applied during discovery and development activities to provide a solubility range, which would assist placement of the drug within the BCS/DCS and rationalise drug and formulation decisions.

Fasted Intestinal Solubility Limits and Distributions Applied to the Biopharmaceutics and Developability Classification Systems

After oral administration, a drug’s solubility in intestinal fluid is an important parameter influencing bioavailability and if the value is known it can be applied to estimate multiple biopharmaceutical parameters including the solubility limited absorbable dose. Current in vitro measurements may utilise fasted human intestinal fluid (HIF) or simulated intestinal fluid (SIF) to provide an intestinal solubility value. This single point value is limited since its position in relation to the fasted intestinal solubility envelope is unknown. In this study we have applied a nine point fasted equilibrium solubility determination in SIF, based on a multi-dimensional analysis of fasted human intestinal fluid composition, to seven drugs that were previously utilised to investigate the developability classification system (ibuprofen, mefenamic acid, furosemide, dipyridamole, griseofulvin, paracetamol and acyclovir). The resulting fasted equilibrium solubility envelope encompasses literature solubility values in both HIF and SIF indicating that it measures the same solubility space as current approaches with solubility behaviour consistent with previous SIF design of experiment studies. In addition, it identifies that three drugs (griseofulvin, paracetamol and acyclovir) have a very narrow solubility range, a feature that single point solubility approaches would miss. The measured mid-point solubility value is statistically equivalent to the value determined with the original fasted simulated intestinal fluid recipe, further indicating similarity and that existing literature results could be utilised as a direct comparison. Since the multi-dimensional approach covered greater than ninety percent of the variability in fasted intestinal fluid composition, the measured maximum and minimum equilibrium solubility values should represent the extremes of fasted intestinal solubility and provide a range. The seven drugs all display different solubility ranges and behaviours, a result also consistent with previous studies. The dose/solubility ratio for each measurement point can be plotted using the developability classification system to highlight individual drug behaviours. The lowest solubility represents a worst-case scenario which may be useful in risk-based quality by design biopharmaceutical calculations than the mid-point value. The method also permits a dose/solubility ratio frequency distribution determination for the solubility envelope which permits further risk-based refinement, especially where the drug crosses a classification boundary. This novel approach therefore provides greater in vitro detail with respect to possible biopharmaceutical performance in vivo and an improved ability to apply risk-based analysis to biopharmaceutical performance. Further studies will be required to expand the number of drugs measured and link the in vitro measurements to in vivo results.

Impact of Simulated Intestinal Fluids on Dissolution, Solution Chemistry, and Membrane Transport of Amorphous Multidrug Formulations

The solution behavior and membrane transport of multidrug formulations were herein investigated in a biorelevant medium simulating fasted conditions. Amorphous multidrug formulations were prepared by the solvent evaporation method. Combinations of atazanavir (ATV) and ritonavir (RTV) and felodipine (FDN) and indapamide (IPM) were prepared and stabilized by a polymer for studying their dissolution (under non-sink conditions) and membrane transport in fasted state simulated intestinal fluid (FaSSIF). The micellar solubilization by FaSSIF enhanced the amorphous solubility of the drugs to different extents. Similar to buffer, the maximum achievable concentration of drugs in combination was reduced in FaSSIF, but the extent of reduction was affected by the degree of FaSSIF solubilization. Dissolution studies of ATV and IPM revealed that the amorphous solubility of these two drugs was not affected by FaSSIF solubilization. In contrast, RTV was significantly affected by FaSSIF solubilization with a 30% reduction in the maximum achievable concentration upon combination to ATV, compared to 50% reduction in buffer. This positive deviation by FaSSIF solubilization was not reflected in the mass transport–time profiles. Interestingly, FDN concentrations remain constant until the amount of IPM added was over 1000 μg/mL. No decrease in the membrane transport of FDN was observed for a 1:1 M ratio of FDN-IPM combination. This study demonstrates the importance of studying amorphous multidrug formulations under physiologically relevant conditions to obtain insights into the performance of these formulations after oral administration.

Small scale in vitro method to determine a bioequivalent equilibrium solubility range for fasted human intestinal fluid

Drug solubility is a key parameter controlling oral absorption, but intestinal solubility is difficult to assess in vitro. Human intestinal fluid (HIF) aspirates can be applied but they are variable, difficult to obtain and expensive. Simulated intestinal fluids (SIF) are a useful surrogate but multiple recipes are available and the optimum is unknown. A recent study characterised fasted HIF aspirates using a multi-dimensional approach and determined nine bioequivalent SIF media recipes that represented over ninety percent of HIF compositional variability. In this study these recipes have been applied to determine the equilibrium solubility of twelve drugs (naproxen, indomethacin, phenytoin, piroxicam, aprepitant, carvedilol, zafirlukast, tadalafil, fenofibrate, griseofulvin, felodipine, probucol) previously investigated using a statistical design of experiment (DoE) approach. The bioequivalent solubility measurements are statistically equivalent to the previous DoE, enclose literature solubility values in both fasted HIF and SIF, and the solubility range is less than the previous DoE. These results indicate that the system is measuring the same solubility space as literature systems with the lower overall range suggesting improved equivalence to in vivo solubility, when compared to DoEs. Three drugs (phenytoin, tadalafil and griseofulvin) display a comparatively narrow solubility range, a behaviour that is consistent with previous studies and related to the drugs' molecular structure and properties. This solubility behaviour would not be evident with single point solubility measurements. The solubility results can be analysed using a custom DoE to determine the most statistically significant factor within the media influencing solubility. This approach has a lower statistical resolution than a formal DoE and is not appropriate if determination of media factor significance for solubilisation is required. This study demonstrates that it is possible to assess the fasted intestinal equilibrium solubility envelope using a small number of bioequivalent media recipes obtained from a multi-dimensional analysis of fasted HIF. The derivation of the nine bioequivalent SIF media coupled with the lower measured solubility range indicate that the solubility results are more likely to reflect the fasted intestinal solubility envelope than previous DoE studies and highlight that intestinal solubility is a range and not a single value.

Supersaturation and Solubilization upon In Vitro Digestion of Fenofibrate Type I Lipid Formulations: Effect of Droplet Size, Surfactant Concentration and Lipid Type

Lipid-based formulations (LBF) enhance oral drug absorption by promoting drug solubilization and supersaturation. The aim of the study was to determine the effect of the lipid carrier type, drop size and surfactant concentration on the rate of fenofibrate release in a bicarbonate-based in vitro digestion model. The effect of the lipid carrier was studied by preparing type I LBF with drop size ≈ 2 µm, based on medium-chain triglycerides (MCT), sunflower oil (SFO), coconut oil (CNO) and cocoa butter (CB). The drop size and surfactant concentration effects were assessed by studying MCT and SFO-based formulations with a drop size between 400 nm and 14 µm and surfactant concentrations of 1 or 10%. A filtration through a 200 nm filter followed by HPLC analysis was used to determine the aqueous fenofibrate, whereas lipid digestion was followed by gas chromatography. Shorter-chain triglycerides were key in promoting a faster drug release. The fenofibrate release from long-chain triglyceride formulations (SFO, CNO and CB) was governed by solubilization and was enhanced at a smaller droplet size and higher surfactant concentration. In contrast, supersaturation was observed after the digestion of MCT emulsions. In this case, a smaller drop size and higher surfactant had negative effects: lower peak fenofibrate concentrations and a faster onset of precipitation were observed. The study provides new mechanistic insights on drug solubilization and supersaturation after LBF digestion, and may support the development of new in silico prediction models.

Mechanisms of drug solubilization by polar lipids in biorelevant media

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. The solubilization of fenofibrate by 13 phospholipids, 11 fatty acids and 2 monoglycerides was studied by an in vitro model of the upper GI tract. The main trends were verified with progesterone and danazol. It was revealed that to alter drug solubilization in biorelevant media, the polar lipids must form mixed colloidal aggregates with the bile. Such aggregates are formed when: (1) the polar lipid is used at a sufficiently high concentration (relative to its mixed critical micellar concentration) and (2) its hydrophobic chain has a melting temperature (T_m) < 37 °C. When these two conditions are met, the increased polar lipid chain length increases the drug solubilization capacity. Hence, long chain (C18) unsaturated polar lipids show best drug solubilization, due to the combination of long chain length and low T_m. Polar lipids with T_m significantly higher than 37 °C (e.g. C16 and C18 saturated compounds) do not impact drug solubilization in biorelevant media, due to limited association in mixed colloidal aggregates. The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order [choline phospholipids] > [monoglycerides] > [fatty acids]. As both the acyl chain and head group types are structural features of the polar lipids, and not of the solubilized drugs, the described trends in drug solubilization should hold true for a variety of hydrophobic molecules.

Multidimensional analysis of human intestinal fluid composition

The oral administration of solid dosage forms is the commonest method to achieve systemic therapy and relies on the drug's solubility in human intestinal fluid (HIF), a key factor that influences bioavailability and biopharmaceutical classification. However, HIF is difficult to obtain and is known to be variable, which has led to the development of a range of simulated intestinal fluid (SIF) systems to determine drug solubility in vitro. In this study we have applied a novel multidimensional approach to analyse and characterise HIF composition using a published data set in both fasted and fed states with a view to refining the existing SIF approaches. The data set provided 152 and 172 measurements of five variables (total bile salt, phospholipid, total free fatty acid, cholesterol and pH) in time-dependent HIF samples from 20 volunteers in the fasted and fed state, respectively. The variable data sets for both fasted state and fed state are complex, do not follow normal distributions but the amphiphilic variable concentrations are correlated. When plotted 2-dimensionally a generally ellipsoid shaped data cloud with a positive slope is revealed with boundaries that enclose published fasted or fed HIF compositions. The data cloud also encloses the majority of fasted state and fed state SIF recipes and illustrates that the structured nature of design of experiment (DoE) approaches does not optimally cover the variable space and may examine media compositions that are not biorelevant. A principal component analysis in either fasted or fed state in combination with fitting an ellipsoid shape to enclose the data results in 8 points that capture over 95% of the compositional variability of HIF. The variable's average rate of concentration change in both fasted state and fed state over a short time scale (10 min) is zero and a Euclidean analysis highlights differences between the fasted and fed states and among individual volunteers. The results indicate that a 9-point DoE (8 + 1 central point) could be applied to investigate drug solubility in vitro and provide statistical solubility limits. In addition, a single point could provide a worst-case solubility measurement to define the lowest biopharmaceutical classification boundary or for use during drug development. This study has provided a novel description of HIF composition. The approach could be expanded in multiple ways by incorporation of further data sets to improve the statistical coverage or to cover specific patient groups (e.g., paediatric). Further development might also be possible to analyse information on the time dependent behaviour of HIF and to guide HIF sampling and analysis protocols.

Small scale design of experiment investigation of equilibrium solubility in simulated fasted and fed intestinal fluid

It is widely recognised that drug solubility within the gastrointestinal tract (GIT) differs from values determined in a simple aqueous buffer and to circumvent this problem measurement in biorelevant fluids is determined. Biorelevant fluids are complex mixtures of components (sodium taurocholate, lecithin, sodium phosphate, sodium chloride, pancreatin and sodium oleate) at various concentrations and pH levels to provide systems simulating fasted (FaSSIF) or fed (FeSSIF) intestinal media. Design of Experiment (DoE) studies have been applied to investigate FaSSIF and FeSSIF and indicate that a drug's equilibrium solubility varies over orders of magnitude, is influenced by the drug type and individual or combinations of media components, with some of these interactions being drug specific. Although providing great detail on the drug media interactions these studies are resource intensive requiring up to ninety individual experiments for FeSSIF. In this paper a low sample number or reduced DoE system has been investigated by restricting components with minimal solubility impact to a single value and only investigating variations in the concentrations of sodium taurocholate, lecithin, sodium oleate, pH and additionally in the case of fed media, monoglyceride. This reduces the experiments required to ten (FaSSIF) and nine (FeSSIF). Twelve poorly soluble drugs (Ibuprofen, Valsartan, Zafirlukast, Indomethacin, Fenofibrate, Felodipine, Probucol, Tadalafil, Carvedilol, Aprepitant, Bromocriptine and Itraconazole) were investigated and the results compared to published DoE studies and literature solubility values in human intestinal fluid (HIF), FaSSIF or FeSSIF. The solubility range determined by the reduced DoE is statistically equivalent to the larger scale published DoE results in over eighty five percent of the cases. The reduced DoE range also covers HIF, FaSSIF or FeSSIF literature solubility values. In addition the reduced DoE provides lowest measured solubility values that agree with the published DoE values in ninety percent of the cases. However, the reduced DoE only identified single and in some cases none of the major components influencing solubility in contrast to the larger published DoE studies which identified multiple individual components and component interactions. The identification of significant components within the reduced DoE was also dependent upon the drug and system under investigation. The study demonstrates that the lower experimental number reduces statistical power of the DoE to resolve the impact of media components on solubility. However, in a situation where only the solubility range is required the reduced DoE can provide the desired information, which will be of benefit during in vitro development studies. Further refinements are possible to extend the reduced DoE protocol to improve biorelevance and application into areas such as PBPK modelling.