Combined assessment of muscle quality and quantity predicts oncological outcome in patients with esophageal cancer.

BACKGROUND: Sarcopenia consists of two dysregulation patterns of body composition, myopenia and myosteatosis. The aim of this study is to compare the preoperative status of various body composition indexes including our newly developed modified intramuscular adipose tissue content (mIMAC) to investigate these clinical values in esophageal cancer patients. METHOD: We assessed preoperative psoas muscle mass index (PMI), IMAC, and mIMAC in 150 esophageal cancer patients. RESULTS: Preoperative high IMAC and low mIMAC status were significantly associated with older age. Preoperative decreased mIMAC was significantly associated with advanced T classification and the presence of distant metastasis and low preoperative mIMAC was an independent prognostic factor for poor overall survival and disease-free survival in esophageal cancer patients. Combined assessment of preoperative mIMAC with PMI could help stratify risk for oncological outcomes. Finally, preoperative PMI and mIMAC were positively correlated with various nutritional factors in esophageal cancer patients. CONCLUSION: Combined assessment between preoperative PMI and mIMAC could stratify risk for oncological outcomes, and preoperative mIMAC might be surrogate marker for aging and nutritional status in esophageal cancer patients.

Bioequivalence of Oral Drug Products in the Healthy and Special Populations: Assessment and Prediction Using a Newly Developed In Vitro System "BE Checker".

In order to assess and predict the bioequivalence (BE) of oral drug products, a new in vitro system "BE checker" was developed, which reproduced the environmental changes in the gastrointestinal (GI) tract by changing the pH, composition, and volume of the medium in a single chamber. The dissolution and membrane permeation profiles of drugs from marketed products were observed in the BE checker under various conditions reflecting the inter-patient variations of the GI physiology. As variable factors, initial gastric pH, gastric emptying time, and GI agitation strength were varied in vitro. Dipyridamole, a basic drug, showed rapid and supersaturated dissolution when the paddle speed in the donor chamber was 200 rpm, which corresponds to the high agitation strength in the stomach. In contrast, supersaturated dissolution disappeared, and the permeated amount decreased under the conditions with a slow paddle speed (100 and 50 rpm) and short gastric emptying time (10 min). In those conditions, disintegration of the formulation was delayed, and the subsequent dissolution of dipyridamole was not completed before the fluid pH was changed to neutral. Similar results were obtained when the initial gastric pH was increased to 3.0, 5.0, and 6.5. To investigate that those factors also affect the BE of oral drug products, dissolution and permeation of naftopidil from its ordinary and orally disintegrating (OD) tablets were observed in the BE checker. Both products showed the similar dissolution profiles when the paddle speed and gastric emptying time were set to 100 rpm and 10 or 20 min, respectively. However, at a low paddle speed (50 rpm), the dissolution of naftopidil from ordinary tablets was slower than that from the OD tablets, and the permeation profiles became dissimilar. These results indicated the possibility of the bioinequivalence of some oral formulations in special patients whose GI physiologies are different from those in the healthy subjects. The BE checker can be a highly capable in vitro tool to assess the BE of oral drug products in various populations.

Critical Impact of Drug-Drug Interactions via Intestinal CYP3A in the Risk Assessment of Weak Perpetrators Using Physiologically Based Pharmacokinetic Models.

A great deal of effort has been being made to improve the accuracy of the prediction of drug-drug interactions (DDIs). In this study, we addressed CYP3A-mediated weak DDIs, in which a relatively high false prediction rate was pointed out. We selected 17 orally administered drugs that have been reported to alter area under the curve (AUC) of midazolam, a typical CYP3A substrate, 0.84-1.47 times. For weak CYP3A perpetrators, the predicted AUC ratio mainly depends on intestinal DDIs rather than hepatic DDIs because the drug concentration in the enterocytes is higher. Thus, DDI prediction using simulated concentration-time profiles in each segment of the digestive tract was made by physiologically based pharmacokinetic (PBPK) modeling software GastroPlus. Although mechanistic static models tend to overestimate the risk to ensure the safety of patients, some underestimation is reported about PBPK modeling. Our in vitro studies revealed that 16 out of 17 tested drugs exhibited time-dependent inhibition (TDI) of CYP3A, and the subsequent DDI simulation that ignored these TDIs provided false-negative results. This is considered to be the cause of past underestimation. Inclusion of the DDI parameters of all the known DDI mechanisms, reversible inhibition, TDI, and induction, which have opposite effects on midazolam AUC, to PBPK model was successful in improving predictability of the DDI without increasing false-negative prediction as trade-off. This comprehensive model-based analysis suggests the importance of the intestine in assessing weak DDIs via CYP3A and the usefulness of PBPK in predicting intestinal DDIs. SIGNIFICANCE STATEMENT: Although drug-drug interaction (DDI) prediction has been extensively performed previously, the accuracy of prediction for weak interactions via CYP3A has not been thoroughly investigated. In this study, we simulate DDIs considering drug concentration-time profile in the enterocytes and discuss the importance and the predictability of intestinal DDIs about weak CYP3A perpetrators.

In Vitro Assessment of Supersaturation/Precipitation and Biological Membrane Permeation of Poorly Water-Soluble Drugs: A Case Study With Albendazole and Ketoconazole.

This study aimed to elucidate the relationship between supersaturation and precipitation and the effect of a supersaturated state on drug membrane permeation. Stock solutions of albendazole (ALB) and ketoconazole (KTZ) dissolved in dimethyl sulfoxide (0.1-50 mg/mL) were diluted 100-fold with buffer solution (pH 6.8, 37°C). In the case of ALB, a supersaturated state and immediate precipitation were observed at 10 µg/mL or less and 20 µg/mL or higher, respectively. When KTZ was used, at an initial concentration of 200 µg/mL or higher, precipitation was observed, although the dissolved concentration remained at approximately 120 µg/mL for at least 30 min. These dissolved concentrations of ALB and KTZ related to approximately 10-fold and 14-fold over the saturated solubility from respective bulk powder. An in vitro permeation study implied that the rate of drug permeation across a biological membrane increased with increasing supersaturation. These results suggested favorable strategies for development of a supersaturable formulation could depend on the precipitation properties of the drug. Immediate- and controlled-release forms might be suitable for supersaturable formulations for KTZ and ALB, respectively.

Effects of gastric pH on oral drug absorption: In vitro assessment using a dissolution/permeation system reflecting the gastric dissolution process.

The aim of the present study was to evaluate the effects of gastric pH on the oral absorption of poorly water-soluble drugs using an in vitro system. A dissolution/permeation system (D/P system) equipped with a Caco-2 cell monolayer was used as the in vitro system to evaluate oral drug absorption, while a small vessel filled with simulated gastric fluid (SGF) was used to reflect the gastric dissolution phase. After applying drugs in their solid forms to SGF, SGF solution containing a 1/100 clinical dose of each drug was mixed with the apical solution of the D/P system, which was changed to fasted state-simulated intestinal fluid. Dissolved and permeated amounts on applied amount of drugs were then monitored for 2h. Similar experiments were performed using the same drugs, but without the gastric phase. Oral absorption with or without the gastric phase was predicted in humans based on the amount of the drug that permeated in the D/P system, assuming that the system without the gastric phase reflected human absorption with an elevated gastric pH. The dissolved amounts of basic drugs with poor water solubility, namely albendazole, dipyridamole, and ketoconazole, in the apical solution and their permeation across a Caco-2 cell monolayer were significantly enhanced when the gastric dissolution process was reflected due to the physicochemical properties of basic drugs. These amounts resulted in the prediction of higher oral absorption with normal gastric pH than with high gastric pH. On the other hand, when diclofenac sodium, the salt form of an acidic drug, was applied to the D/P system with the gastric phase, its dissolved and permeated amounts were significantly lower than those without the gastric phase. However, the oral absorption of diclofenac was predicted to be complete (96-98%) irrespective of gastric pH because the permeated amounts of diclofenac under both conditions were sufficiently high to achieve complete absorption. These estimations of the effects of gastric pH on the oral absorption of poorly water-soluble drugs were consistent with observations in humans. In conclusion, the D/P system with the gastric phase may be a useful tool for better predicting the oral absorption of poorly water-soluble basic drugs. In addition, the effects of gastric pH on the oral absorption of poorly water-soluble drugs may be evaluated by the D/P system with and without the gastric phase.

An Assessment of the Oral Bioavailability of Three Ca-Channel Blockers Using a Cassette-Microdose Study: A New Strategy for Streamlining Oral Drug Development.

A cassette-microdose (MD) clinical study was performed to demonstrate its usefulness for identifying the most promising compound for oral use. Three Ca-channel blockers (nifedipine, nicardipine, and diltiazem) were chosen as model drugs. In the MD clinical study, a cassette-dose method was employed in which three model drugs were administered simultaneously. Both intravenous (i.v.) and oral (p.o.) administration studies were conducted to calculate the oral bioavailability (BA). For comparison, p.o. studies with therapeutic dose (ThD) levels were also performed. In all studies, blood concentrations of each drug were successfully determined using liquid chromatography-mass spectrometry with the lower limit of quantification of 0.2-2.0 pg/mL. Oral BA of nifedipine in the MD study was approximately 50% and in the same range with that obtained in the ThD study, whereas other two drugs showed significantly lower BA in the MD study, indicating a dose-dependent absorption. In addition, compared with the ThD study, absorption of nicardipine was delayed in the MD study. As a result, nifedipine was considered to be most promising for oral use. In conclusion, a cassette-MD clinical study is of advantage for oral drug development that enables to identify the candidate having desired properties for oral use.

Quantitative assessment of intestinal first-pass metabolism of oral drugs using portal-vein cannulated rats.

PURPOSE: To evaluate the impact of intestinal first-pass metabolism (Fg) by cytochrome P4503A (CYP3A) and uridine 5'-diphosphate-glucuronosyltransferases (UGT) on in vivo oral absorption of their substrate drugs. METHODS: CYP3A and UGT substrates were orally administered to portal-vein cannulated (PV) rats to evaluate their intestinal availability (Fa · Fg). In the case of CYP3A substrates, vehicle or 1-aminobenzotriazole (ABT), a potent inhibitor of CYP enzymes, was pretreated to assess Fg separately from Fa (Enzyme-inhibition method). On the other hand, since potent inhibitors of UGT have not been identified, Fg of UGT substrate was calculated from total amount of metabolites generated in enterocytes (Metabolite-distribution method). RESULTS: After oral administration of CYP3A substrates in ABT-pretreated rats, the portal and systemic plasma concentrations of the metabolite were nearly the same, indicating almost complete inhibition of intestinal CYP3A-mediated metabolism. Using Enzyme-inhibition method, Fg of midazolam (1 mg/kg) was calculated as 0.71. Additionally, total amount of raloxifene-6-glucuronide generated in enterocytes after oral administration of raloxifene was estimated using Metabolite-distribution method and Fg of raloxifene (0.98 µmol/kg) was calculated as 0.21. CONCLUSIONS: PV rats enabled in vivo quantitative assessment of intestinal first-pass metabolism by CYP3A and UGT. This method is useful for clarifying the cause of low bioavailability.

Assessment of absorption potential of poorly water-soluble drugs by using the dissolution/permeation system.

This study aims to assess the absorption potential of oral absorption of poorly water-soluble drugs by using the dissolution/permeation system (D/P system). The D/P system can be used to perform analysis of drug permeation under dissolution process and can predict the fraction of absorbed dose in humans. When celecoxib at 1/100 of a clinical dose was applied to the D/P system, percentage of dose dissolved and permeated significantly decreased with an increase in the applied amount, resulting in the oral absorption being predicted to be 22-55%. Whereas similar dissolution and permeation profiles of montelukast sodium were observed, estimated absorption (69-85%) was slightly affected. Zafirlukast absorption (33-36%) was not significantly affected by the dose, although zafirlukast did not show complete dissolution. The relationship between clinical dose and predicted oral absorption of drugs corresponded well to clinical observations. The limiting step of the oral absorption of celecoxib and montelukast sodium was solubility, while that of zafirlukast was dissolution rate. However, due to high permeability of montelukast, oral absorption was not affected by dose. Therefore, the D/P system is a useful tool to assess the absorption potential of poorly water-soluble drugs for oral use.

In vivo assessment of the impact of efflux transporter on oral drug absorption using portal vein-cannulated rats.

The purpose of this study was to evaluate the impact of intestinal efflux transporters on the in vivo oral absorption process. Three model drugs-fexofenadine (FEX), sulfasalazine (SASP), and topotecan (TPT)-were selected as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and P-gp and BCRP substrates, respectively. The drugs were orally administered to portal vein-cannulated rats after pretreatment with zosuquidar (ZSQ), P-gp inhibitor, and/or Ko143, BCRP inhibitor. Intestinal availability (Fa·Fg) of the drugs was calculated from the difference between portal and systemic plasma concentrations. When rats were orally pretreated with ZSQ, Fa·Fg of FEX increased 4-fold and systemic clearance decreased to 75% of the control. In contrast, intravenous pretreatment with ZSQ did not affect Fa·Fg of FEX, although systemic clearance decreased significantly. These data clearly show that the method presented herein using portal vein-cannulated rats can evaluate the effects of intestinal transporters on Fa·Fg of drugs independently of variable systemic clearance. In addition, it was revealed that 71% of FEX taken up into enterocytes underwent selective efflux via P-gp to the apical surface, while 79% of SASP was effluxed by Bcrp. In the case of TPT, both transporters were involved in its oral absorption. Quantitative analysis indicated a 3.5-fold higher contribution from Bcrp than P-gp. In conclusion, the use of portal vein-cannulated rats enabled the assessment of the impact of efflux transporters on intestinal absorption of model drugs. This experimental system is useful for clarifying the cause of low bioavailability of various drugs.

Assessment of intestinal availability of various drugs in the oral absorption process using portal vein-cannulated rats.

To understand the rate-limiting process of oral drug absorption, not only total bioavailability (F) but also intestinal (F(a) · F(g)) and hepatic (F(h)) availability after oral administration should be evaluated. Usually, F(a) · F(g) of drug is calculated from pharmacokinetic parameters after intravenous and oral administration. This approach is influenced markedly by the estimated value of F(h), which varies with the hepatic blood flow used in the calculations. In this study, portal vein-cannulated rats were used to calculate the F(a) · F(g) of drugs from a single oral dosing experiment without data from intravenous injection. Portal vein-cannulated rats were prepared by a new operative method that enables stable portal vein blood flow. This surgery had no effects on hepatic blood flow and metabolic activity. Our method for calculating F(a) · F(g) was validated by determining both portal and systemic plasma concentration profiles of various drugs possessing different pharmacokinetic properties after oral administration to the portal vein-cannulated rats. Simulation of portal and systemic plasma concentrations by physiologically based pharmacokinetic modeling indicated that the balance of the absorption rate constant (k(a)) and elimination rate constant (k(e)) resulted in different patterns in portal and systemic plasma concentration-time profiles. This study is expected to provide a new experimental animal model that enables identification of the factors that limit oral bioavailability and to provide pharmacokinetic information on the oral absorption process of drugs during drug discovery.

Site of drug absorption after oral administration: assessment of membrane permeability and luminal concentration of drugs in each segment of gastrointestinal tract.

This study was conducted to assess the site of drug absorption in the gastrointestinal (GI) tract after oral administration. Drug permeability to different regions of rat intestine, jejunum, ileum and colon, was measured by in situ single-pass perfusion method. It was revealed that the epithelial surface area should not be a determinant of the regional difference in the intestinal permeability of highly permeable drugs. Effects of the mucus layer at the surface of the epithelium and the fluidity of the epithelial cell membrane on the drug permeability were investigated. These factors are demonstrated to contribute to the regional differences in intestinal drug permeability. The luminal drug concentration in each segment of the GI tract after oral administration was measured directly in fasted rats. Water ingested orally was absorbed quickly in the jejunum and the luminal fluid volume was diminished in the middle to lower part of the small intestine. According to the absorption of water luminal concentration of atenolol, a drug with low permeability, was elevated and exceeded the initial dose concentration. In contrast, the concentration of highly permeable drugs, antipyrine and metoprolol, decreased quickly in the upper part of the intestine and a significant amount of drugs was not detected in the lower jejunum and the ileum. From the time-profiles of luminal drug concentration, fraction of dose absorbed from each segment of the GI tract was calculated. Both antipyrine and metoprolol were found to be absorbed quickly at the upper part of the small intestine. In addition, the possible contribution of gastric absorption was demonstrated for these drugs. The pattern of site-dependent absorption of atenolol showed the higher absorbability in the middle and lower portion of the jejunum. These informations on site-dependent absorption of drugs are considered to be important for effective oral delivery systems.

Effect of food intake on the oral absorption of poorly water-soluble drugs: in vitro assessment of drug dissolution and permeation assay system.

The aim of the present work was to establish appropriate conditions for the dissolution/permeation system (D/P system) to estimate the effect of food intake on oral drug absorption. The D/P system is an in vitro assay system to evaluate the drug dissolution and permeation processes after oral administration. Caco-2 monolayer was used as a model membrane of the intestinal epithelium. In this study, two types of simulated intestinal fluid reflecting the fasted and the fed state conditions of the human gastrointestinal tract were used. Drugs were applied to the D/P system as a powder, then, permeated amounts of drugs into the basal side were monitored. A sigmoidal correlation was obtained between in vivo oral absorption (% absorbed of dose) and in vitro permeated amount (% of dose/2 h) under both states. From the D/P system, the estimated absorption of albendazole in both states was found to correspond well with in vivo observation. Moreover, the D/P system could estimate the effect of self-emulsifying formulation on the oral absorption of danazol, quantitatively. In conclusion, the D/P system was proved to be a useful assay system not only for the oral absorption of drugs, but also for the food effect on the absorption.