Viscosity-mediated negative food effect on oral absorption of poorly-permeable drugs with an absorption window in the proximal intestine: In vitro experimental simulation and computational verification

Supersaturation of zafirlukast in fasted and fed state intestinal media with and without precipitation inhibitors

Poor water solubility is a bottle neck in the development of many new drug candidates, and understanding and circumventing this is essential for a more effective drug development. Zafirlukast (ZA) is a leukotriene antagonist marketed for the treatment of asthma (Accolate®). ZA is poorly water soluble, and is formulated in an amorphous form (aZA) to improve its solubility and oral bioavailability. It has been shown that upon dissolution of aZa, the concentration of ZA in solution is supersaturated with respect to its stable crystalline form (ZA monohydrate), and thus, in theory, the bioavailability increases upon amorphization of ZA. The polymers hydroxypropylmethylcellulose (HPMC) and polyvinylpyrrolidone (PVP), often used as stabilizers of the supersaturated state, are in the excipient list of Accolate®. It is not recommended to take Accolate® with food, as this reduces the bioavailability by 40%. The aim of this study was to investigate the effect of simulated fasted and fed state intestinal media as well as the effect of HPMC and PVP on the supersaturation and precipitation of ZA in vitro. Supersaturation of aZA was studied in vitro in a small scale setup using the μDiss Profiler™. Several media were used for this study: One medium simulating the fasted state intestinal fluids and three media simulating different fed state intestinal fluids. Solid state changes of the drug were investigated by small angle x-ray scattering. The duration wherein aZA was maintained at a supersaturated state was prolonged in the presence of HPMC and lasted more than 20h in the presence of PVP in a fasted state intestinal medium. The presence of PVP increased the concentration of drug dissolved in the supersaturated state. The duration of supersaturation was shorter in fed than in a fasted state simulated intestinal media, but the concentration during supersaturation was higher. It was thus not possible to predict any positive or negative food effects from the dissolution/precipitation curves from different media. Lipolysis products in the fed state simulated media seemed to cause both a negative effect on the duration of supersaturation, and an increased drug concentration during supersaturation. In contrast, when testing the effect of a fed state simulated medium compared to the fasted state medium, in the presence of PVP, a clear negative effect was seen on the dissolution/precipitation curved of the fed state medium. The drug concentration during supersaturation was marginally different in the two media, but a precipitation of ZA was seen in the fed state medium, which was not observed in the fasted state medium. Solid state transformation from aZA to ZA monohydrate (mhZA) upon precipitation of the supersaturated solutions was confirmed by small angle x-ray scattering. All of these results can explain the described in vivo behavior of ZA. For ZA simple dissolution experiments in vitro can be used to examine supersaturation, effectiveness of PI and potential food effects on these.

In vitro biorelevant models for evaluating modified release mesalamine products to forecast the effect of formulation and meal intake on drug release

AIMS

Postprandial administration of solid oral dosage forms greatly changes the dissolution environment compared to fasted state administration. The aims of this study were to investigate and forecast the effect of co-administration of a meal on drug release for delayed and/or extended release mesalamine formulations as well as design of in vitro tests to distinguish among formulations in a biorelevant way.

METHODS

Five different mesalamine formulations (Asacol® 400 mg, Mezavant® 1200 mg, Pentasa® 500 mg and Salofalk® in the 250 mg and 500 mg strengths) were investigated with biorelevant dissolution methods using the USP apparatus III and USP apparatus IV (open loop mode) under both fasted and fed state conditions, as well as with the dissolution methods described in pharmacopeia for delayed and extended release mesalamine products.

RESULTS

Using the biorelevant experimental conditions proposed in this study, changes in release in the proximal gut due to meal intake are forecast to be minimal for Asacol®, Mezavant®, Pentasa® and Salofalk® 500 mg, while for Salofalk® 250 mg release was predicted to occur much earlier under fed state conditions. The USP apparatus III generally tended to result in faster dissolution rates and forecast more pronounced food effects for Salofalk® 250 mg than the USP apparatus IV. The biorelevant dissolution gradients were also able to reflect the in vivo behavior of the formulations.

CONCLUSIONS

In vitro biorelevant models can be useful in the comparison of the release behavior from different delayed and extended release mesalamine formulations as well as forecasting effects of concomitant meal intake on drug release.

Paracetamol as a Post Prandial Marker for Gastric Emptying, A Food-Drug Interaction on Absorption

The use of paracetamol as tool to determine gastric emptying was evaluated in a cross over study. Twelve healthy volunteers were included and each of them consumed two low and two high caloric meals. Paracetamol was mixed with a liquid meal and administered by a nasogastric feeding tube. The post prandial paracetamol plasma concentration time curve in all participants and the paracetamol concentration in the stomach content in six participants were determined. It was found that after paracetamol has left the stomach, based on analysis of the stomach content, there was still a substantial rise in the plasma paracetamol concentration time curve. Moreover, the difference in gastric emptying between high and low caloric meals was missed using the plasma paracetamol concentration time curve. The latter curves indicate that (i) part of the paracetamol may leave the stomach much quicker than the meal and (ii) part of the paracetamol may be relatively slowly absorbed in the duodenum. This can be explained by the partition of the homogenous paracetamol-meal mixture in the stomach in an aqueous phase and a solid bolus. The aqueous phase leaves the stomach quickly and the paracetamol in this phase is quickly absorbed in the duodenum, giving rise to the relatively steep increase of the paracetamol concentration in the plasma. The bolus leaves the stomach relatively slowly, and encapsulation by the bolus results in relatively slow uptake of paracetamol from the bolus in the duodenum. These findings implicate that paracetamol is not an accurate post prandial marker for gastric emptying. The paracetamol concentration time curve rather illustrates the food-drug interaction on absorption, which is not only governed by gastric emptying.

Investigating the cubosomal ability for transnasal brain targeting: In vitro optimization, ex vivo permeation and in vivo biodistribution

The aim of this study was to enhance the risperidone delivery to the brain through the transnasal route via optimization of cubosomal gel. Cubosomes were prepared using glycerol mono-oleate (GMO), Pluronic F127 (PF127) and Tween 80 (T80). The prepared formulae were characterized by testing their particle size, polydispersity index, zeta potential, entrapment efficiency, in vitro drug release and transmission electron microscopy. Central composite design was planned for the formulae optimization and the selected formula (containing PF127 with concentration 15 mg/g GMO and T80 with concentration of 20mg/L) was re-prepared in presence of gelling polymer (gellan gum or polyox). The optimal cubosomal gel (containing 0.4% w/v polyox) had been subjected to ex-vivo permeation, histopathological evaluation and in vivo biodistribution studies. It showed significantly higher transnasal permeation and better distribution to the brain, when compared to the used control (drug solution and/or suspension). Finally, the cubosomal gel could be considered as a promising carrier for brain targeting of CNS acting drugs through the transnasal route.

Food Effect in Humans: Predicting the Risk Through In Vitro Dissolution and In Vivo Pharmacokinetic Models

In vitro and in vivo experimental models are frequently used to assess a new chemical entity's (NCE) biopharmaceutical performance risk for food effect (FE) in humans. Their ability to predict human FE hinges on replicating key features of clinical FE studies and building an in vitro-in vivo relationship (IVIVR). In this study, 22 compounds that span a wide range of physicochemical properties, Biopharmaceutics Classification System (BCS) classes, and food sensitivity were evaluated for biorelevant dissolution in fasted- and fed-state intestinal media and the dog fed/fasted-state pharmacokinetic model. Using the area under the curve (AUC) as a performance measure, the ratio of the fed-to-fasted AUC (FE ratio) was used to correlate each experimental model to FE ratio in humans. A linear correlation was observed for the in vitro dissolution-human IVIVR (R (2) = 0.66, % mean square error 20.7%). Similarly, the dog FE ratio correlated linearly with the FE ratio in humans (R (2) = 0.74, % mean square error 16.25%) for 15 compounds. Data points near the correlation line indicate dissolution-driven mechanism for food effect, while deviations from the correlation line shed light on unique mechanisms that can come into play such as GI physiology or unusual physicochemical properties. In summary, fed/fasted dissolution studies and dog PK studies show a reasonable correlation to human FE, hence are useful tools to flag high-risk NCEs entering clinical development. Combining kinetic dissolution, dog FE model and in silico modeling one can study FE mechanism and formulation strategies to mitigate the FE risk.

In vitro-in vivo-in silico approach in biopharmaceutical characterization of ibuprofen IR and SR tablets

Within the last decades, physiologically based pharmacokinetic models have emerged into a biopharmaceutical toolkit that has been proven useful in understanding how physicochemical, formulation and physiological factors affect oral drug absorption. The purpose of this study was to develop a drug specific physiologically based pharmacokinetic model that will allow mechanistic interpretation of oral absorption from dosage forms exhibiting different in vitro and different in vivo performance (i.e. immediate release and sustained release tablets) and identification of bioperformance dissolution testing. Ibuprofen was chosen to be used for the "proof of concept" considering it is well characterised and the necessary physicochemical, biopharmaceutical and pharmacokinetic properties for model development could be found in the literature. Gastrointestinal simulation technology implemented in Simcyp® was successful in estimating ibuprofen oral absorption. The developed model exhibited good generalisation ability for the dosage forms studied. The obtained results indicate that the model was sensitive to input kinetics represented by the in vitro drug release profiles obtained under various dissolution conditions. According to the obtained results, reciprocating cylinder apparatus with biorepresentative change in media pH might be considered as bioperformance dissolution in the case of the two ibuprofen SR products studied. These results further justify the use of integrated in vitro-in vivo-in silico approach in estimating bioperformance of oral solid dosage forms.

Variability in bioavailability of small molecular tyrosine kinase inhibitors

Small molecular tyrosine kinase inhibitors (smTKIs) are in the centre of the very quickly expanding area of personalized chemotherapy and oral applicability thereof. The number of drugs in this class is rapidly growing, with twenty current approvals by both the European Medicines Agency (EMA) and the Food and Drug Administration (FDA). The drugs are, however, generally characterized by a poor oral, and thus variable, bioavailability. This results in significant variation in plasma levels and exposure. The cause is a complex interplay of factors, including poor aqueous solubility, issued permeability, membrane transport and enzymatic metabolism. Additionally, food and drug-drug interactions can play a significant role. The issues related with an impaired bioavailability generally receive little attention. To the best of our knowledge, this article is the first to provide an overview of the factors that determine the bioavailability of the smTKIs.