Assessment of food effects during clinical development.

Food-drug interactions frequently hamper oral drug development due to various physicochemical, physiological and formulation-dependent mechanisms. This has stimulated the development of a range of promising biopharmaceutical assessment tools which, however, lack standardized settings and protocols. Hence, this manuscript aims to provide an overview of the general approach and the methodology used in food effect assessment and prediction. For in vitro dissolution-based predictions, the expected food effect mechanism should be carefully considered when selecting the level of complexity of the model, together with its drawbacks and advantages. Typically, in vitro dissolution profiles are then incorporated into physiologically based pharmacokinetic models, which can estimate the impact of food-drug interactions on bioavailability within 2-fold prediction error, at least. Positive food effects related to drug solubilization in the GI tract are easier to predict than negative food effects. Preclinical animal models also provide a good level of food effect prediction, with beagle dogs remaining the gold standard. When solubility-related food-drug interactions have large clinical impact, advanced formulation approaches can be used to improve fasted state pharmacokinetics, hence decreasing the fasted/fed difference in oral bioavailability. Finally, the knowledge from all studies should be combined to secure regulatory approval of the labelling instructions.

Assessment of physiological barriers to nutrition following critical illness.

BACKGROUND & AIMS: Nutrition may be important for recovery from critical illness. Gastrointestinal dysfunction is a key barrier to nutrition delivery in the Intensive Care Unit (ICU) and metabolic rate is elevated exacerbating nutritional deficits. Whether these factors persist following ICU discharge is unknown. We assessed whether delayed gastric emptying (GE) and impaired glucose absorption persist post-ICU discharge. METHODS: A prospective observational study was conducted in mechanically ventilated adults at 3 time-points: in ICU (V1); on the post-ICU ward (V2); and 3-months after ICU discharge (V3); and compared to age-matched healthy volunteers. On each visit, all participants received a test-meal containing 100 ml of 1 kcal/ml liquid nutrient, labelled with 0.1 g 13C-octanoic acid and 3 g 3-O-Methyl-glucose (3-OMG), and breath and blood samples were collected over 240min to quantify GE (gastric emptying coefficient (GEC)), and glucose absorption (3-OMG concentration; area under the curve (AUC)). Data are mean ± standard error of the mean (SEM) and differences shown with 95% confidence intervals (95%CI). RESULTS: Twenty-six critically ill patients completed V1 (M:F 20:6; 62.0 ± 2.9 y; BMI 29.8 ± 1.2 kg/m2; APACHE II 19.7 ± 1.9), 15 completed V2 and eight completed V3; and were compared to 10 healthy volunteers (M:F 6:4; 60.5 ± 7.5 y; BMI 26.0 ± 1.0 kg/m2). GE was significantly slower on V1 compared to health (GEC difference: -0.96 (95%CI -1.61, -0.31); and compared to V2 (-0.73 (-1.16, -0.31) and V3 (-1.03 (-1.47, -0.59). GE at V2 and V3 were not different to that in health (V2: -0.23 (-0.61, 0.14); V3: 0.10 (-0.27, 0.46)). GEC: V1: 2.64 ± 0.19; V2: 3.37 ± 0.12; V3: 3.67 ± 0.10; health: 3.60 ± 0.13. Glucose absorption (3-OMG AUC0-240) was impaired on V1 compared to V2 (-37.9 (-64.2, -11.6)), and faster on V3 than in health (21.8 (0.14, 43.4) but absorption at V2 and V3 did not differ from health. Intestinal glucose absorption: V1: 63.8 ± 10.4; V2: 101.7 ± 7.0; V3: 111.9 ± 9.7; health: 90.7 ± 3.8. CONCLUSION: This study suggests that delayed GE and impaired intestinal glucose absorption recovers rapidly post-ICU. This requires further confirmation in a larger population. The REINSTATE trial was prospectively registered at www.anzctr.org.au. TRIAL ID: ACTRN12618000370202.

Simultaneous assessment of intestinal permeability and lactase activity in human-milk-fed preterm infants by sugar absorption test: Clinical implementation and analytical method.

BACKGROUND & AIMS: Experimental (nutritional) interventions in preterm infants frequently focus on intestinal maturation, as improving tolerance to enteral nutrition is a major goal. Intestinal permeability and lactase activity serve as markers for intestinal maturation. We aimed to develop a protocol for the simultaneous assessment of both markers in human-milk-fed preterm infants by a sugar absorption test. In addition, we developed a new gas chromatography-mass spectrometry (GC-MS) method for the analysis of lactulose, lactose, and mannitol in urine and milk collected during the sugar absorption test. METHODS: The sugar absorption test was performed on days 4, 7, and 14 postpartum in 12 preterm infants (gestational age of 26-32 weeks). Human milk was collected, pooled, and divided into equal portions to provide a stable lactose intake for 24 h. Urine was collected in the last 6 h of this 24 h period, after administration of a bolus test sugar solution. Samples were analyzed by GC-MS after derivatization by oxime formation combined with acetylation. RESULTS: The GC-MS method was validated and used for the accurate measurement of lactulose, lactose, and mannitol concentrations. The urinary lactulose/mannitol ratio declined with time, suggesting a decreased intestinal permeability. The urine-to-milk-lactulose/lactose ratio increased as a result of increased lactase activity with time. CONCLUSIONS: The developed protocol for simultaneous assessment of intestinal permeability and lactase activity can be used to monitor the effect of experimental (nutritional) interventions in human-milk-fed preterm infants. Urine and milk samples obtained during the sugar absorption test can be accurately analyzed by GC-MS.

Pharmacokinetics Comparison, Intestinal Absorption and Acute Toxicity Assessment of a Novel Water-Soluble Astragaloside IV Derivative (Astragalosidic Acid, LS-102).

BACKGROUND AND OBJECTIVES: Astragaloside IV (AGS IV) is the most important bioactive constituent of Radix Astragali. However, its disappointing clinical application is mainly caused by its very low solubility in biologic fluids, resulting in poor bioavailability after oral administration. We recently obtained a novel water-soluble derivative of AGS IV (astragalosidic acid, LS-102) that displayed significant cardioprotective potential against hypoxia-induced injury. The objective of this study was to investigate the intestinal absorption, main pharmacokinetic parameters and acute toxicity of LS-102 in rodents compared with AGS IV. METHODS: An oral dose of LS-102 and AGS IV (20 mg/kg) was administered to Sprague-Dawley (SD) rats, and blood samples were collected at predetermined time points. The plasma concentrations were detected by a validated UHPLC-MS/MS method, and pharmacokinetic parameters were calculated using a compartmental model. In the intestinal permeability study, the transport of LS-102 across Caco-2 cell monolayers was investigated at six concentrations from 6.25 to 250 µM. Moreover, the acute toxicity of LS-102 (40-5000 mg/kg) via a single oral administration was investigated in BALB/c mice. RESULTS: LS-102 was rapidly absorbed, attaining a maximum concentration of 248.7 ± 22.0 ng/ml at 1.0 ± 0.5 h after oral administration. The relative bioavailability of LS-102 was twice that of AGS IV. LS-102 had a Papp (mean) of 15.72-25.50 × 10-6 cm/s, which was almost 500-fold higher than that of AGS IV, showing that LS-102 had better transepithelial permeability and could be better absorbed in the intestinal tract. The acute toxicity study showed no abnormal changes or mortality in mice treated with LS-102 even at the single high dose of 5000 mg/kg body weight. CONCLUSIONS: Oral LS-102 produced a pharmacokinetic profile different from AGS IV with higher bioavailability, while the toxic tolerance was similar to previous estimates. Thus, we speculated that LS-102 might provide better clinical efficacy and be a potential candidate for the new drug development of Radix Astragali.

Preclinical Bioavailability Strategy for Decisions on Clinical Drug Formulation Development: An In Depth Analysis.

The aim of the presented retrospective analysis was to verify whether a previously proposed Janssen Biopharmaceutical Classification System (BCS)-like decision tree, based on preclinical bioavailability data of a solution and suspension formulation, would facilitate informed decision making on the clinical formulation development strategy. In addition, the predictive value of (in vitro) selection criteria, such as solubility, human permeability, and/or a clinical dose number (Do), were evaluated, potentially reducing additional supporting formulation bioavailability studies in animals. The absolute ( Fabs,sol) and relative ( Frel, susp/sol) bioavailability of an oral solution and suspension, respectively, in rat or dog and the anticipated BCS classification were analyzed for 89 Janssen compounds with 28 of these having Frel,susp/sol and Fabs,sol in both rat and dog at doses around 10 and 5 mg/kg, respectively. The bioavailability outcomes in the dog aligned well with a BCS-like classification based upon the solubility of the active pharmaceutical ingredient (API) in biorelevant media, while the alignment was less clear for the bioavailability data in the rat. A retrospective analysis on the clinically tested formulations for a set of 12 Janssen compounds confirmed that the previously proposed animal bioavailability-based decision tree facilitated decisions on the oral formulation type, with the dog as the most discriminative species. Furthermore, the analysis showed that based on a Do for a standard human dose of 100 mg in aqueous and/or biorelevant media, a similar formulation type would have been selected compared to the one suggested by the animal data. However, the concept of a Do did not distinguish between solubility enhancing or enabling formulations and does not consider the API permeability, and hence, it produces the risk of slow and potentially incomplete oral absorption of an API with poor intestinal permeability. In cases where clinical dose estimations are available early in development, the preclinical bioavailability studies and dose number calculations, used to guide formulation selection, may be performed at more relevant doses instead of the proposed standard human dose. It should be noted, however, that unlike in late development, there is uncertainty on the clinical dose estimated in the early clinical phases because that dose is usually only based on in vitro and/or in vivo animal pharmacology models, or early clinical biomarker information. Therefore, formulation strategies may be adjusted based on emerging data supporting clinical doses. In summary, combined early information on in vitro-assessed API solubility and permeability, preclinical suspension/solution bioavailability data in relation to the intravenous clearance, and metabolic pathways of the API can strengthen formulation decisions. However, these data may not always fully distinguish between conventional (e.g., to be taken with food), enhancing, and enabling formulations. Therefore, to avoid overinvestment in complex and expensive enabling technologies, it is useful to evaluate a conventional and solubility (and/or permeability) enhancing formulation under fasted and fed conditions, as part of a first-in-human study or in a subsequent early human bioavailability study, for compounds with high Do, a low animal Frel,susp/sol, or low Fabs,sol caused by precipitation of the solubilized API.

Assessment of Passive Intestinal Permeability Using an Artificial Membrane Insert System.

Despite reasonable predictive power of current cell-based and cell-free absorption models for the assessment of intestinal drug permeability, high costs and lengthy preparation steps hamper their use. The use of a simple artificial membrane (without any lipids present) as intestinal barrier substitute would overcome these hurdles. In the present study, a set of 14 poorly water-soluble drugs, dissolved in 2 different media (fasted state simulated/human intestinal fluids [FaSSIF/FaHIF]), were applied to the donor compartment of an artificial membrane insert system (AMI-system) containing a regenerated cellulose membrane. Furthermore, to investigate the predictive capacity of the AMI-system as substitute for the well-established Caco-2 system to assess intestinal permeability, the same set of 14 drugs dissolved in FaHIF were applied to the donor compartment of a Caco-2 system. For 14 drugs, covering a broad range of physicochemical parameters, a reasonable correlation between both absorption systems was observed, characterized by a Pearson correlation coefficient r of 0.95 (FaHIF). Using the AMI-system, an excellent predictive capacity of FaSSIF as surrogate medium for FaHIF was demonstrated (r = 0.96). Based on the acquired data, the AMI-system appears to be a time- and cost-effective tool for the early-stage estimation of passive intestinal permeability for poorly water-soluble drugs.

Impact of the US FDA "Biopharmaceutics Classification System" (BCS) Guidance on Global Drug Development.

The FDA guidance on application of the biopharmaceutics classification system (BCS) for waiver of in vivo bioequivalence (BE) studies was issued in August 2000. Since then, this guidance has created worldwide interest among biopharmaceutical scientists in regulatory agencies, academia, and industry toward its implementation and further expansion. This article describes how the review implementation of this guidance was undertaken at the FDA and results of these efforts over last dozen years or so across the new, and the generic, drug domains are provided. Results show that greater than 160 applications were approved, or tentatively approved, based on the BCS approach across multiple therapeutic areas; an additional significant finding was that at least 50% of these approvals were in the central nervous system (CNS) area. These findings indicate a robust utilization of the BCS approach toward reducing unnecessary in vivo BE studies and speeding up availability of high quality pharmaceutical products. The article concludes with a look at the adoption of this framework by regulatory and health policy organizations across the globe, and FDA's current thinking on areas of improvement of this guidance.

Teduglutide for treatment of adult patients with short bowel syndrome.

INTRODUCTION: The European Society for Clinical Nutrition has published recommendations on the 'definition and classification of intestinal failure (IF)'. Two criteria must be present: a 'decreased absorption of macronutrients and/or water and electrolytes due to a loss of gut function' and the 'need for parenteral support'. Home parenteral support (HPS) is the primary treatment for chronic IF but is associated with complications. Areas covered: The principal cause of chronic IF is short bowel syndrome (SBS). The aim of treatment is to maximize intestinal absorption and reduce or eliminate the need for HPS to achieve the best possible quality of life. Teduglutide, an analog of glucagon-like peptide 2, improves intestinal rehabilitation by promoting mucosal growth, reducing intestinal loss and promoting intestinal absorption. This article provides an overview and opinion on teduglutide for SBS. Expert opinion: Teduglutide may provide a new treatment strategy for SBS patients with chronic IF. When prescribed, patients should be informed of the benefits and risks of the drug and must be closely monitored in an expert center. Furthermore, as this treatment is costly, cost-effectiveness analysis as well as the risk-benefit ratio needs to be better evaluated.

In vitro assessment on effect of duodenal contents on the lead (Pb2+) binding capacity of two probiotic bacterial strains.

In vitro Lead (Pb2+) binding capacity of two probiotic bacteria strains, namely Bifidobacterium longumBB79 and Lactobacillus pentosusITA23, was assessed following incubation with the intestinal contents (IC) of laying hens. Results of this study demonstrated that IC treatment significantly enhanced (P<0.01) Pb2+ binding capacity of both bacterial strains. Fourier transform infrared analysis indicated that several functional groups (O-H or N-H, C-H, CË­O, C-O, and C-O-C) on the bacteria cell wall involved in metal ion binding were altered after IC incubation, and new groups appeared between the 3700cm-1 and 4000cm-1bands. Transmission electron microscopy demonstrated that after incubation with IC, unidentified IC components created new binding sites on the bacterial cell surface. These particles also changed the mechanism of Pb2+ binding of the two strains from intracellular accumulation to extracellular adsorption.

Assessment of intestinal malabsorption.

Significant efforts have been made in the last decade to either standardize the available tests for intestinal malabsorption or to develop new, more simple and reliable techniques. The quest is still on and, unfortunately, clinical practice has not dramatically changed. The investigation of intestinal malabsorption is directed by the patient's history and baseline tests. Endoscopy and small bowel biopsies play a major role although non-invasive tests are favored and often performed early on the diagnostic algorithm, especially in paediatric and fragile elderly patients. The current clinically available methods and research tools are summarized in this review article.

Assessment of In Vivo Clinical Product Performance of a Weak Basic Drug by Integration of In Vitro Dissolution Tests and Physiologically Based Absorption Modeling.

Effective integration of in vitro tests and absorption modeling can greatly improve our capability in understanding, comparing, and predicting in vivo performances of clinical drug products. In this case, we used a proprietary drug candidate galunisertib to describe the procedures of designing key in vitro tests, analyzing relevant experimental and trial data, and integrating them into physiologically based absorption models to evaluate the performances of its clinical products. By simulating the preclinical study result, we estimated high in vivo permeability for the drug. Given the high sensitivity of its solubility to pH, supersaturation may play an important role in the absorption of galunisertib. Using the dynamic dissolution test, i.e., artificial stomach-duodenum (ASD) model and simulation, we concluded galunisertib in solution or tablet products could maintain supersaturation during the transit in the gastrointestinal tract (GIT). A physiologically based absorption model was established by incorporating these key inputs in the simulation of Trial 1 results of galunisertib solution. To predict the performance of three tablet products, we developed z-factor dissolution models from the multi-pH USP dissolution results and integrate them into the absorption model. The resultant biopharmaceutical models provided good prediction of the extent of absorption of all three products, but underestimated the rate of absorption of one tablet product. Leveraging the ASD result and optimization with the dissolution model, we identified the limitation of the model due to complexity of estimating the dissolution parameter z and its in vitro-in vivo correlation.

Risk assessment for extending the Biopharmaceutics Classification System-based biowaiver of immediate release dosage forms of fluconazole in adults to the paediatric population.

OBJECTIVES: The paediatric population undergoes developmental changes in gastric pH, gastric emptying, intestinal transit time, membrane permeability, protein binding, body water, distribution and metabolism. It is widely recognised that changes in these parameters may result in an alteration of the plasma profile and thus in key bioequivalence parameters such as Cmax (maximum plasma concentration of drug) and area under the plasma concentration vs time profile curve. The aim of this work is to assess the risk of extending the biowaiver for immediate release dosage formulations of fluconazole from the adult to the paediatric population. METHODS AND KEY FINDINGS: Fluconazole exhibits good solubility and very rapid dissolution characteristics in various pH media. The absorption of fluconazole in children is known to be complete (over 90%) and not impaired by elevated pH, which is prevalent during the early days of life. Dose numbers calculated using body surface area are less than 1. Therefore, the risk to drug absorption due to differences in gastric pH, gastric emptying, intestinal transit, membrane permeability and metabolising enzymes between adults and children is considered low. CONCLUSIONS: Thus, it can be safely concluded that fluconazole meets highly soluble and highly permeable criteria in the paediatric population and can be allocated to class 1 of the Biopharmaceutics Classification System (BCS) for this population as well as in adults. Additionally, fluconazole has an excellent safety profile in children, similar to that in adults. The BCS-based biowaiver claimed in adults can be safely extended to the paediatric population provided that the requirements in excipient selection and dissolution profile comparison using BCS-based dissolution conditions as stated in the biowaiver monograph for fluconazole immediate release dosage forms in adults are fulfilled.

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.

Bomb calorimetry, the gold standard for assessment of intestinal absorption capacity: normative values in healthy ambulant adults.

BACKGROUND: Intestinal absorption capacity is considered to be the best method for assessing overall digestive intestinal function. Earlier reference values for intestinal function in healthy Dutch adults were based on a study that was conducted in an inpatient metabolic unit setting in a relatively small series. The present study aimed to readdress and describe the intestinal absorption capacity of healthy adults, who were consuming their usual (Western European) food and beverage diet, in a standard ambulatory setting. METHODS: Twenty-three healthy subjects (aged 22-60 years) were included in the analyses. Nutritional intake (energy and macronutrients) was determined with a 4-day nutritional diary. Subsequently, mean faecal losses of energy (by bomb calorimetry), fat, protein and carbohydrate were determined following a 3-day faecal collection. Finally, intestinal absorption capacity was calculated from the differences between intake and losses. RESULTS: Mean (SD) daily faeces production was 141 (49) g (29% dry weight), containing 891 (276) kJ [10.7 (1.3) kJ g(-1) wet faeces; 22.6 (2.5) kJ g(-1) dry faeces], 5.2 (2.2) g fat, 10.0 (3.8) g protein and 29.7 (11.7) g carbohydrates. Mean (SD) intestinal absorption capacity of healthy subjects was 89.4% (3.8%) for energy, 92.5% (3.7%) for fat, 86.9% (6.4%) for protein and 87.3% (6.6%) for carbohydrates. CONCLUSIONS: The present study provides normative values for both stool nutrient composition and intestinal energy and macronutrient absorption in healthy adults on a regular Dutch diet in an ambulatory setting. Intestinal energy absorption was found to be approximately 90%.

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.

Rethinking iron regulation and assessment in iron deficiency, anemia of chronic disease, and obesity: introducing hepcidin.

Adequate iron availability is essential to human development and overall health. Iron is a key component of oxygen-carrying proteins, has a pivotal role in cellular metabolism, and is essential to cell growth and differentiation. Inadequate dietary iron intake, chronic and acute inflammatory conditions, and obesity are each associated with alterations in iron homeostasis. Tight regulation of iron is necessary because iron is highly toxic and human beings can only excrete small amounts through sweat, skin and enterocyte sloughing, and fecal and menstrual blood loss. Hepcidin, a small peptide hormone produced mainly by the liver, acts as the key regulator of systemic iron homeostasis. Hepcidin controls movement of iron into plasma by regulating the activity of the sole known iron exporter ferroportin-1. Downregulation of the ferroportin-1 exporter results in sequestration of iron within intestinal enterocytes, hepatocytes, and iron-storing macrophages reducing iron bioavailability. Hepcidin expression is increased by higher body iron levels and inflammation and decreased by anemia and hypoxia. Importantly, existing data illustrate that hepcidin may play a significant role in the development of several iron-related disorders, including the anemia of chronic disease and the iron dysregulation observed in obesity. Therefore, the purpose of this article is to discuss iron regulation, with specific emphasis on systemic regulation by hepcidin, and examine the role of hepcidin within several disease states, including iron deficiency, anemia of chronic disease, and obesity. The relationship between obesity and iron depletion and the clinical assessment of iron status will also be reviewed.

Assessment of intestinal permeability in (premature) neonates by sugar absorption tests.

Infants born prematurely have an enhanced intestinal permeability compared to healthy term infants. This enhanced permeability might be a contributing factor in the development of Necrotising Enterocolitis. The assessment of intestinal permeability in premature neonates with sugar absorption tests has been proven to be safe and of minimal burden to the infant. After enteral administration of a test solution containing lactulose and mannitol, the excretion of these sugars is measured in urine, and the ratio is calculated. The lactulose and mannitol concentrations in urine can be measured by the use of a gas chromatograph after pre-purification and derivatisation of the sample. Non-invasive assessment of intestinal permeability can be useful in monitoring the effects of experimental (nutritional) therapy.

Surface area assessment of the murine intestinal tract as a prerequisite for oral dose translation from mouse to man.

In many pharmacological and toxicological studies knowledge about the intestinal absorption, which is dependent upon the surface area of absorptive epithelia, is indispensible. Although mice are often used in such preclinical studies, very few quantitative data about their intestinal surface area are available. Especially for locally acting candidate drugs in development, this information is crucial for dose translation towards humans. Therefore, the surface area of the intestinal tract of CD-1 IGS mice was assessed in the present study. The intestinal tracts of 12 mice were collected after euthanasia. From six animals, histological sections from the duodenum, jejunum, ileum, caecum and colon-rectum were made according to common stereological principles. Using these sections, the volumes and surface areas of each intestinal segment were estimated applying stereological counting procedures. In the other six animals, the density and surface area of the microvilli present in each intestinal segment were determined by means of scanning and transmission electron microscopy to assess the increase of the intestinal surface area attributable to the presence of microvilli. The mean total volume and surface area of the intestinal tract were 1.34 cm(3) and 1.41 m(2), respectively. The relative intestinal surface area (intestinal surface area divided by the body surface area) was 119. The relative intestinal surface area of mice is very similar to that of humans. The results of this study are important for the appropriate dose translation of candidate therapeutic compounds in drug development from mouse to humans.

Theoretical investigation of passive intestinal membrane permeability using Monte Carlo method to generate drug-like molecule population.

The purpose of the present study was to investigate the effect of the physiological and morphological differences between in vivo and in vitro systems on the estimation of in vivo effective intestinal membrane permeability (P(eff)) from in vitro permeability data (P(ivt,app)). Five hundred virtual drug-like compounds were generated using Monte Carlo method based on the distribution of octanol water partition coefficient, molecular weight, and pK(a). In vivo and in vitro membrane permeability was theoretically calculated from these parameters considering the transcellular, paracellular and unstirred water layer (UWL) permeation. More than 50% of drug-like compounds showed high P(eff) values. When the same pH value was used for in vivo and in vitro, the scattering of the P(ivt,app)-P(eff) plot was small, whereas it was large when different pH values were used. However, the extent of discrepancy depended on the physicochemical properties and permeation characteristics of a drug. When the pH effect was directly corrected on the P(eff) value, paracellular and UWL permeability was inappropriately corrected since the pH partition theory is only applicable for transcellular permeation. In vivo species differences of P(eff) and the fraction of a dose absorbed (Fa%) was also investigated for humans, rats and dogs. In conclusion, P(eff) estimation from in vitro data should be based on the theoretical method rather than simple linear regression.

The role of the endocannabinoid system in the regulation of energy expenditure.

Endocannabinoids, a lipid-derived signaling system, regulate appetite and motivation to eat via effects in the hypothalamus and nucleus accumbens. Not all the effects of endocannabinoids on fat mass can be explained by the regulation of food intake alone. Endocannabinoids and their receptors are located in areas of the central nervous system and multiple peripheral tissues involved in the regulation of intermediary metabolism and energy expenditure. In addition to regulating food intake by both central and peripherally mediated effects, endocannabinoids modify glucose and lipid metabolism so as to promote energy storage via lipogenesis and reduce energy expenditure. The endocannabinoid system appears to be overactive in obesity and may serve to maintain fat mass and underlies some of the metabolic consequences of obesity. Inhibition of the cannabinoid type-1 receptor ameliorates the effects of endocannabinoids on food intake and energy metabolism; lipogenesis is inhibited, lipolysis, fatty acid oxidation and glucose uptake increase.