Colloidal carriers for controlled drug delivery and targeting: Modification, characterization and in vivo distribution : by Rainer H. Muller, Wissenschaftliche Verlagsgesellschaft, Stuttgart, Germany, 1991,227 figures, DM168

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30334/1/0000736.pd

Particle diffusional layer thickness in a USP dissolution apparatus II: A combined function of particle size and paddle speed

This work was to investigate the effects of particle size and paddle speed on the particle diffuisonal layer thickness h app in a USP dissolution apparatus II. After the determination of the powder dissolution rates of five size fractions of fenofibrate, including <20, 20–32, 32–45, 63–75, and 90–106 µm, the present work shows that the dependence of h app on particle size follows different functions in accordance with the paddle speed. At 50 rpm, the function of h app is best described by a linear plot of $h_{{rm app}} = 9.91sqrt d - 23.31$ ( R 2  = 0.98) throughout the particle diameter, d , from 6.8 to 106 µm. In contrast, at 100 rpm a transitional particle radius, r , of 23.7 µm exists, under which linear relationship h app  = 1.59 r ( R 2  = 0.98) occurs, but above which h app becomes a constant of 43.5 µm. Thus, h app changes not only with particle size, but also with the hydrodynamics under standard USP configurations, which has been overlooked in the past. Further, the effects of particle size and paddle speed on h app were combined using dimensionless analysis. Within certain fluid velocity/particle regime, linear correlation of h app / d with the square-root of Reynolds number $(dvarpi /upsilon )^{1/2}$ , that is, $h_{{rm app}} /d = 1.5207 - 9.25 times 10^{ - 4} (dvarpi /nu )^{1/2}$ ( R 2  = 0.9875), was observed. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4815–4829, 2008Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61209/1/21345_ftp.pd

Viscosity modulates blood glucose response to nutrient solutions in dogs

The relationship between postprandial blood glucose levels and meal viscosity was studied by adding various combinations of hydroxypropylmethylcellulose to glucose solutions and administering them to female mongrel dogs. Glucose was administered as 5% or 20% solutions in water. Hydroxypropylmethylcellulose was dissolved in the glucose solutions to yield low (5000 cP measured at 37[deg]C and 1 s-1), medium (15 000 cP) or high (30 000 cP) viscosities. High viscosity hydroxypropylmethylcellulose significantly reduced the maximum blood glucose concentration, Cmax, by 60% (5% glucose meal) and 40% (20% glucose meal) while reducing the area under the blood level vs. time curve (AUC0-3 h) by 40-50%. Medium viscosity hydroxypropylmethylcellulose reduced the Cmax at both glucose levels, but reduced the AUC only for the 5% glucose meal. Low viscosity HPMC lowered the Cmax only after the 5% glucose meal, and had no significant effect on the AUC at either glucose level. The average time to reach maximum concentration, Tmax, was prolonged two- to three-fold at all viscosity levels for the 5% glucose solutions, but was not affected when 20% glucose solutions were administered. It was concluded that hydroxypropylmethylcellulose can effectively retard the absorption of glucose from the gastrointestinal tract, and that the extent of this effect is related to the viscosity of the solution administered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29912/1/0000269.pd

Establishing virtual bioequivalence and clinically relevant specifications using in vitro biorelevant dissolution testing and physiologically-based population pharmacokinetic modeling. Case example:Naproxen

Background Physiologically-based population pharmacokinetic modeling (popPBPK) coupled with in vitro biopharmaceutics tools such as biorelevant dissolution testing can serve as a powerful tool to establish virtual bioequivalence and set clinically relevant specifications. One of several applications of popPBPK modeling is in the emerging field of virtual bioequivalence (VBE), where it can be used to streamline drug development by implementing model-informed formulation design and to inform regulatory decision-making e.g., with respect to evaluating the possibility of extending BCS-based biowaivers beyond BCS Class I and III compounds in certain cases. Methods In this study, Naproxen, a BCS class II weak acid was chosen as the model compound. In vitro biorelevant solubility and dissolution experiments were performed and the resulting data were used as an input to the PBPK model, following a stepwise workflow for the confirmation of the biopharmaceutical parameters. The naproxen PBPK model was developed by implementing a middle-out approach and verified against clinical data obtained from the literature. Once confidence in the performance of the model was achieved, several in vivo dissolution scenarios, based on model-based analysis of the in vitro data, were used to simulate clinical trials in healthy adults. Inter-occasion variability (IOV) was also added to critical physiological parameters and mechanistically propagated through the simulations. The various trials were simulated on a “worst/best case” dissolution scenario and average bioequivalence was assessed according to Cmax, AUC and Tmax. Results VBE results demonstrated that naproxen products with in vitro dissolution reaching 85% dissolved within 90 min would lie comfortably within the bioequivalence limits for Cmax and AUC. Based on the establishment of VBE, a dissolution “safe space” was designed and a clinically relevant specification for naproxen products was proposed. The interplay between formulation-related and drug-specific PK parameters (e.g., t1/2) to predict the in vivo performance was also investigated. Conclusion Over a wide range of values, the in vitro dissolution rate is not critical for the clinical performance of naproxen products and therefore naproxen could be eligible for BCS-based biowaivers based on in vitro dissolution under intestinal conditions. This approach may also be applicable to other poorly soluble acidic compounds with long half-lives, providing an opportunity to streamline drug development and regulatory decision-making without putting the patient at a risk

Establishing virtual bioequivalence and clinically relevant specifications using in vitro biorelevant dissolution testing and physiologically-based population pharmacokinetic modeling. Case example:Naproxen

Background: Physiologically-based population pharmacokinetic modeling (popPBPK) coupled with in vitro biopharmaceutics tools such as biorelevant dissolution testing can serve as a powerful tool to establish virtual bioequivalence and set clinically relevant specifications. One of several applications of popPBPK modeling is in the emerging field of virtual bioequivalence (VBE), where it can be used to streamline drug development by implementing model-informed formulation design and to inform regulatory decision-making e.g., with respect to evaluating the possibility of extending BCS-based biowaivers beyond BCS Class I and III compounds in certain cases. Methods: In this study, Naproxen, a BCS class II weak acid was chosen as the model compound. In vitro biorelevant solubility and dissolution experiments were performed and the resulting data were used as an input to the PBPK model, following a stepwise workflow for the confirmation of the biopharmaceutical parameters. The naproxen PBPK model was developed by implementing a middle-out approach and verified against clinical data obtained from the literature. Once confidence in the performance of the model was achieved, several in vivo dissolution scenarios, based on model-based analysis of the in vitro data, were used to simulate clinical trials in healthy adults. Inter-occasion variability (IOV) was also added to critical physiological parameters and mechanistically propagated through the simulations. The various trials were simulated on a “worst/best case” dissolution scenario and average bioequivalence was assessed according to Cmax, AUC and tmax. Results: VBE results demonstrated that naproxen products with in vitro dissolution reaching 85% dissolved within 90 minutes would lie comfortably within the bioequivalence limits for Cmax and AUC. Based on the establishment of VBE, a dissolution “safe space” was designed and a clinically relevant specification for naproxen products was proposed. The interplay between formulation-related and drug-specific PK parameters (e.g., t1/2) to predict the in vivo performance was also investigated. Conclusion: Over a wide range of values, the in vitro dissolution rate is not critical for the clinical performance of naproxen products and therefore naproxen could be eligible for BCS-based biowaivers based on in vitro dissolution under intestinal conditions. This approach may also be applicable to other poorly soluble acidic compounds with long half-lives, providing an opportunity to streamline drug development and regulatory decision-making without putting the patient at a risk

Establishing virtual bioequivalence and clinically relevant specifications using in vitro biorelevant dissolution testing and physiologically-based population pharmacokinetic modeling. Case example:Naproxen

Background: Physiologically-based population pharmacokinetic modeling (popPBPK) coupled with in vitro biopharmaceutics tools such as biorelevant dissolution testing can serve as a powerful tool to establish virtual bioequivalence and set clinically relevant specifications. One of several applications of popPBPK modeling is in the emerging field of virtual bioequivalence (VBE), where it can be used to streamline drug development by implementing model-informed formulation design and to inform regulatory decision-making e.g., with respect to evaluating the possibility of extending BCS-based biowaivers beyond BCS Class I and III compounds in certain cases. Methods: In this study, Naproxen, a BCS class II weak acid was chosen as the model compound. In vitro biorelevant solubility and dissolution experiments were performed and the resulting data were used as an input to the PBPK model, following a stepwise workflow for the confirmation of the biopharmaceutical parameters. The naproxen PBPK model was developed by implementing a middle-out approach and verified against clinical data obtained from the literature. Once confidence in the performance of the model was achieved, several in vivo dissolution scenarios, based on model-based analysis of the in vitro data, were used to simulate clinical trials in healthy adults. Inter-occasion variability (IOV) was also added to critical physiological parameters and mechanistically propagated through the simulations. The various trials were simulated on a “worst/best case” dissolution scenario and average bioequivalence was assessed according to C max, AUC and T max. Results: VBE results demonstrated that naproxen products with in vitro dissolution reaching 85% dissolved within 90 min would lie comfortably within the bioequivalence limits for C max and AUC. Based on the establishment of VBE, a dissolution “safe space” was designed and a clinically relevant specification for naproxen products was proposed. The interplay between formulation-related and drug-specific PK parameters (e.g., t1/2) to predict the in vivo performance was also investigated. Conclusion: Over a wide range of values, the in vitro dissolution rate is not critical for the clinical performance of naproxen products and therefore naproxen could be eligible for BCS-based biowaivers based on in vitro dissolution under intestinal conditions. This approach may also be applicable to other poorly soluble acidic compounds with long half-lives, providing an opportunity to streamline drug development and regulatory decision-making without putting the patient at a risk. </p

Physicochemical and physiological mechanisms for the effects of food on drug absorption: The role of lipids and pH

Drugs are absorbed after oral administration as a consequence of a complex array of interactions between the drug, its formulation, and the gastrointestinal (GI) tract. The presence of food within the GI tract impacts significantly on transit profiles, pH, and its solubilization capacity. Consequently, food would be expected to affect the absorption of co‐administered drugs when their physicochemical properties are sensitive to these changes. The physicochemical basis by which ingested food/lipids induce changes in the GI tract and influence drug absorption are reviewed. The process of lipid digestion is briefly reviewed and considered in the context of the absorption of poorly water‐soluble drugs. The effect of food on GI pH is reviewed in terms of location (stomach, upper and lower small intestine) and the temporal relationship between pH and drug absorption. Case studies are presented in which postprandial changes in bioavailability are rationalized in terms of the sensitivity of the physicochemical properties of the administered drug to the altered GI environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97269/1/1_ftp.pd

Meeting report: International workshop on implementation of biowaivers based on the biopharmaceutics classification system (BCS)

Even though the pivotal article stating the theoretical basis for a biopharmaceutics drug classification (1) was published almost 20 years ago, the extension of BCS-based biowaiver decisions to drugs belonging to BCS classes other than those showing high solubility and high permeability has not yet reached a consensus among regulators, industrial scientists, and academics. Also, within some jurisdictions, BCS principles have not yet been incorporated into legal frameworks and thus have not been used to allow science- and risk-based regulatory flexibility. This report provides a brief description of the presentations from the International Workshop on Implementation of Biowaivers based on the BCS in Buenos Aires, Argentina, that took place on March 5–6, 2015. The meeting was cosponsored by National University of La Plata, Confederación Farmacéutica Argentina, International Pharmaceutical Federation (FIP), and the American Association of Pharmaceutical Scientists (AAPS). The main objectives of the meeting were to describe the state of the art with respect to in vitro and in silico tools to support waiving in vivo bioequivalence studies and to foster discussion about implementing BCS-based biowaiver decisions to support generic drug registration in South America. Two hundred and fifteen scientists from universities, the pharmaceutical industry, and regulatory authorities took part in this meetingFacultad de Ciencias Exacta