The prodrug mycophenolate mofetil (MMF), which is presystemically hydrolyzed into the pharmacologically active compound mycophenolic acid (MPA), has been widely used for the prophylaxis of acute allograft rejection in solid organ transplantation. However, the huge variability in the plasma concentration level makes the development of MMF drug products difficult due to the great challenge of meeting the traditional bioequivalence (BE) limits. Numerous models have been developed in the past decade to explain the variability, with the emphasis on characterizing the enterohepatic circulation. While the variability arising from systemic appearance can also contribute to the remarkable MPA variability to a great extent, it has been ignored for long for this Biopharmaceutics Classification System class 2 drug. To improve the design of the BE study for this highly variable (HV) drug, the variability of MMF pharmacokinetic (PK) profiles focusing on the absorption process was explored in a population approach. A total of 81 Chinese adult liver transplant recipients were enrolled and had their plasma concentrations of MPA and its metabolites measured by HPLC during one visit or multiple visits in a long-term MMF regimen. The population models were developed using NONMEM, and the data and the results of the model were analyzed by R. Two population PK models of MMF focusing on the absorption process were developed based on the plasma concentrations of MPA and its major metabolite 7-O-MPA-β-glucuronide (MPAG). The MPA PK profiles were best characterized by a two-compartment disposition model with zero inter-individual variability (IIV) of elimination coefficient (K20), lag time, but considerable intra-individual variability (IAV) in the form of inter-occasion variability regarding systemic appearance coefficient, K20, and central volume of distribution, when just using MPA plasma concentrations as observations. The second model took into consideration the EHC by including MPAG profiles as well. The results from both models showcased that the IAV played a far more significant role than the IIV in accounting for the variability of the MMF systemic appearance. This is in line with what was found in the BE study: the within-subject variability (WSV) of BE measures largely exceeded the corresponding between-subject variability. The great WSV of MMF can be mechanistically explained by the interplay of dissolution and solubility with the gastrointestinal (GI) physiological dynamics, especially the gastric emptying (GE) in the fasting state regulated by migrating motor complex, and GE and pH variations in the fed state by the caloric content with irregular patterns of GI motility and secretion. The results implied that for the immediate-release solid oral dosage forms of MMF, running a regular in vitro dissolution test for the fasting state and developing a predictive in vitro dissolution test with sufficient simulation of the GE dynamics and proximal small intestinal pH fluctuations for the fed state would be excellent surrogates for the in vivo BE test. Furthermore, a physiologically based predictive in vitro dissolution test under both fasting and fed conditions would be a new trend for the BE studies of all other HV drug products.

Er-Zhi-Wan (EZW) is a traditional Chinese medicine with many clinical applications and used as a health product in East Asia. Five active ingredients (salidroside, specnuezhenide, nuezhenoside, luteolin, and oleanolic acid) were screened out from EZW to develop an in vitro rapid evaluation method for the classification of in vivo drug absorption behavior by biopharmaceutics classification system (BCS). Ultra-performance liquid chromatography was used for quantitative analysis. Solubility and permeability were assayed by equilibrium solubility and multiple models: everted rat intestinal sac model, cultured Caco-2 cells, octanol-water partition coefficient (LogP) method. The BCS properties of drugs were predicted using software applications, and the correlations of measured and predicted values of factors affecting oral drug absorption were calculated. The results were verified by measuring the absolute bioavailability of the active ingredients. Salidroside, specnuezhenide, and nuezhenoside were classified as BCS class III drugs, and luteolin was classified as a BCS class III/I drug because of the difference in LogP and intestinal permeability. Oleanolic acid was classified as a BCS class II/IV drug in acidic media and BCS class I/III drug in other media. Overall, EZW may be classified as a BCS class III drug, and permeability was identified as the primary factor limiting absorption. The results provide a novel method for the evaluation of the in vivo absorption of oral traditional Chinese medicines.

Single-pass intestinal perfusion( SPIP) is the common carrier of biopharmaceutics classification system( BCS) to study compound permeability. With the application and deepening study of BCS in the field of traditional Chinese medicine( TCM),SPIP model is becoming more and more common to study the intestinal absorption of TCM ingredients. Based on the limitations of the SPIP model in some researches on TCM permeability,it was speculated in this study that aglycone may be more suitable than the glycoside to study the intestinal absorption problem by using SPIP model. Furthermore,applicability of aglycone components was analyzed and evaluated. In this study,with quercetin,daidzein,formononetin,genistein and glycyrrhetinic acid used as research objects,the quantitative study of SPIP was used to evaluate the intestinal permeability of these aglycones and to predict the effective permeability coefficient( Peff) and absorption fraction( Fa) in human body. By combining studies comparison and analysis on multiple permeability research methods and prediction of human body absorption of aglycones in physiological-based pharmacokinetic models,this paper can further illustrate that the SPIP model is a good tool for studying the permeability of aglycones and predicting human absorption,which can provide data foundation and theoretical reference for researches on SPIP technique and BCS in intestinal absorption of TCM ingredients.

The biopharmaceutics classification system( BCS) is a scientific framework or method for classifying drugs based on drug solubility and permeability,which can be used to provide drug bioavailability-absorption correlation analysis. Based on the characteristics of multi-component and multi-target of traditional Chinese medicine( TCM) as well as the concept,method and technology of BCS,the research group proposed biopharmaceutics classification system of Chinese materia medica( CMMBCS) and carried out research and data accumulation of classical prescriptions. Based on the previous research results,further development ideas under the CMMBCS concept and framework were further proposed in this study. In the course of research,the influence of the intermediate links of the complex interactions of the multi-component environment was omitted,and the component absorption studies on the main clinical effects of prescription ingredients were directly concerned,or the components and data were reversely extracted from the aspects of metabolism,pharmacodynamic pathways and absorption principles. Studies were conducted from two aspects( single component and compound prescription) to comprehensively evaluate the absorption properties of TCM compound. In the research path,the different ways in which Chinese medicine could exert its efficacy were fully considered,and CMMBCS classification and establishment rules were clarified mainly by focusing on the absorption pathway into the blood. Specifically,the network pharmacology and molecular docking technology were used to screen the compound index components of TCM; the absorption rules were studied by the physiologically based pharmacokinetic models and the absorption parameters of CMMBCS were calculated by reverse reasoning. Then the CMMBCS classification of TCM prescription was corrected by studying the efficacy or absorption pathway. In this paper,the theoretical framework and research methodology of CMMBCS were systematically improved based on the establishment of CMMBCS basic theory,the supplementary of drug-oriented research ideas and the application of modern mature Chinese medicine methodology.

BACKGROUND: As one of the new drugs of traditional Chinese medicine, Sanye Tablet is employed as a hypolipidemic in the traditional medicine, but the biopharmaceutical properties of the drug is still unclear.
OBJECTIVE: Through the study of biopharmaceutical properties, the classical biopharmaceutics classification system (BCS) can be used to classify and predict the in vivo absorption properties. On this basis, the biopharmaceutical properties closely related to traditional Chinese medicine preparations are added and a modified BCS model is established to predict and judge the absorption degree of traditional Chinese medicine compound.
METHODS: Representative components of Sanye Tablet were selected and subjected to different in vitro tests. The experimental results were compared with the results of the BCS to evaluate the accuracy and applicability to Sanye Tablet. We take parameters of dissolution and stability based on product characteristics into account. A \"modified-BCS\" was developed and the results of the improved method and the classic method were compared. Also the ability of each classification system to predict and determine the extent of absorption of the Chinese herbal compound was investigated based on the absolute bioavailability of representative components.
RESULTS: For classic BCS, the five representative components (except for nuciferine) are all class III, nuciferine is class I/II obtained by Caco-2 cell assay and class III/IV obtained by everted gut sac assay. For modified BCS, paeoniflorin is class III, rutin, hyperoside and salvianolic acid B are class III/IV, and nuciferine is class I/II based on Caco-2 cell assay, class III/IV based on everted gut sac assay. Nuciferine is the best of the five components, with absolute bioavailability reaching 61.91% based on in vivo bioavailability test.
CONCLUSIONS: The five representative components (except for nuciferine) are all class III/IV, which correlates well with the absolute bioavailability results and demonstrates that they are poorly absorbed substances. The correlation between the classification results obtained using the \"modified-BCS\" and absorption in the body is better than the correlation obtained using the classic method, suggesting that the improved BCS is more suitable for the characterization of Sanye Tablet. These results indicate that the oral formulation of Sanye Tablet is a BCS III/IV drug.

The combined clearance of endogenous 6β-hydroxycortisol and 6β-hydroxycortisone is suggested biomarker for in vivo cytochrome P450 3A (CYP3A) activity. We aimed to determine whether the combined clearance of these two markers together with information of biopharmaceutics classification system (BCS) of drugs could be used to predict CYP3A-mediated metabolism of immunosuppressants. The BCS of drug formulations were determined based on the solubility and permeability. Sixty-seven healthy subjects were divided into three groups and group 1 (n = 23), 2 (n = 22), and 3 (n = 22) received oral single dose of cyclosporine, tacrolimus, and sirolimus, respectively. Blood and urine samples were gathered at various times. The combined clearance of 6β-hydroxycortisol and 6β-hydroxycortisone correlated significantly with cyclosporine pharmacokinetics (p < 0.001) after oral dose of a BCS 1 formulation, whereas no relationships were seen after administration of tacrolimus and sirolimus formulations, both of which belonged to BCS 2. Regarding the biopharmaceutical characteristics, the endogenous CYP3A biomarker explains 74.5% of variability in oral cyclosporine clearance between individuals.

1. As a potential new drug candidate for cardiovascular protection and antitumor treatment, the physicochemical properties, gastrointestinal (GI) absorption behaviors and mechanisms of S-propargyl-cysteine (SPRC) were investigated in this study. 2. SPRC exhibited favorable solubility in aqueous media. The log P and log D values were low (≤1.93 ± 0.08). The pKa in the acidic and basic regions was 2.08 ± 0.02 and 8.72 ± 0.03, respectively. The isoelectric point was 5.40 ± 0.02. SPRC was stable in the rat GI fluids, and showed no obvious adsorption and metabolism in the rat GI tract. 3. SPRC displayed poor gastric absorption and favorable intestinal absorption in the rat in situ GI perfusion model. Absorption rate constants (ka), hourly absorption percentage (P) and apparent permeability coefficient (Papp) of SPRC in the small intestine were ≥0.77 ± 0.06 h(-1), 59.25 ± 4.02% and (7.99 ± 0.88) × 10(-5 )cm/s, respectively. Absorption of SPRC exhibited a certain dependence on physiological pH and absorption region. Absorption of SPRC was not inhibited by l-methionine and 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid. 4. SPRC showed favorable oral absorption. It can be categorized as a BCS class I drug. The membrane pore transport appeared to be one of the predominant absorption modes for SPRC.