Identification of novel pregnane X receptor (PXR) agonists by In silico and biological activity analyses and reversal of cigarette smoke-induced PXR downregulation.

Cigarette smoke (CS) contains many toxins that collectively harm nearly every organ in the body, and smoking is a key risk factor for many chronic diseases. Aside from its toxic actions, CS may alter expression of the drug- and steroid-binding pregnane X receptor (PXR), which when activated upregulates expression of cytochrome P450 (CYP) enzymes, glutathione transferases (GSTs), and multidrug resistance protein 1 (MDR1), an adaptive metabolic array that mediates clearance of CS component toxins. We sought to identify new PXR agonists that may be useful for restoring PXR activity in conditions wherein it is suppressed, and their mechanisms of PXR binding and activation. PXR has a uniquely larger, hydrophobic, and highly flexible ligand-binding domain (LBD) vs. other nuclear receptors, enabling it to interact with structurally diverse molecules. We tested certain calcium channel blockers (CCBs) as a pharmacological subset of potential PXR ligands, analyzing by molecular docking methods, and identified a putative active site in the PXR LBD, along with the relevant bonds and bonding energies. We analyzed felodipine binding and agonist activity in detail, as it showed the lowest binding energy among CCBs tested. We found felodipine was a potent PXR agonist as measured by luciferase reporter assay, whereas CCBs with higher binding energies were less potent (amlodipine) or nearly inactive (manidipine), and it induced CYP3A4 expression in HepG2 cells, a known target of PXR agonism. Felodipine also both induced PXR mRNA in HepG2 hepatocytes and reduced CS extract-induced diminution of PXR levels, indicating it modulates PXR expression. The results illuminate mechanisms of ligand-induced PXR activation and identify felodipine as a novel PXR agonist.

Solubility of Pharmaceutical Ingredients in Natural Edible Oils.

Natural edible oils (NEOs) are common excipients for lipid-based formulations. Many of them are complex mixtures comprising hundreds of different triglycerides (TGs). One major challenge in developing lipid-based formulations is the variety in NEO compositions affecting the solubility of active pharmaceutical ingredients. In this work, solubilities of indomethacin (IND), ibuprofen (IBU), and fenofibrate (FFB) in soybean oil and in coconut oil were measured via differential scanning calorimetry, high-performance liquid chromatography, and Raman spectroscopy. Furthermore, this work proposes an approach that mimics NEOs using one key TG and models the API solubilities in these NEOs based on perturbed-chain statistical associating fluid theory (PC-SAFT). Key TGs were determined using the 1,2,3-random hypothesis, and PC-SAFT parameters were estimated via a group-contribution method. Using the proposed approach, the solubility of IBU and FFB was modeled in soybean oil and coconut oil. Furthermore, the solubilities of five more APIs (IND, cinnarizine, naproxen, griseofulvin, and felodipine) were modeled in soybean oil. All modeling results were found in very good agreement with the experimental data. The influence of different NEO kinds on API solubility was examined by comparing FFB and IBU solubilities in soybean oil and refined coconut oil. PC-SAFT was thus found to allow assessing the batch-to-batch consistency of NEO batches in silico.

Dry Gel Containing Optimized Felodipine-Loaded Transferosomes: a Promising Transdermal Delivery System to Enhance Drug Bioavailability.

Felodipine has a very low bioavailability due to first-pass metabolism. The aim of this study was to enhance its bioavailability by transdermal application. Felodipine-loaded transferosomes were prepared by thin-film hydration using different formulation variables. An optimized formula was designed using statistical experimental design. The independent variables were the used edge activator, its molar ratio to phosphatidylcholine, and presence or absence of cholesterol. The responses were entrapment efficiency of transferosomes, their size, polydispersity index, zeta potential, and percent drug released after 8 h. The optimized formula was subjected to differential scanning calorimetry studies and its stability on storage at 4°C for 6 months was estimated. This formula was improved by incorporation of different permeation enhancers where ex vivo drug flux through mice skin was estimated and the best improved formula was formulated in a gel and lyophilized. The prepared gel was subjected to in vivo study using Plendil® tablets as a reference. According to the calculated desirability, the optimized transferosome formula was that containing sodium deoxycholate as edge activator at 5:1 M ratio to phosphatidylcholine and no cholesterol. The thermograms of this formula indicated the incorporation of felodipine inside the prepared vesicles. None of the tested parameters differed significantly on storage. The lyophilized gel of labrasol-containing formula was chosen for in vivo study. The relative bioavailability of felodipine from the designed gel was 1.7. In conclusion, topically applied lyophilized gel containing felodipine-loaded transferosomes is a promising transdermal delivery system to enhance its bioavailability.

Studies on Core-Shell Nanocapsules of Felodipine: In Vitro-In Vivo Evaluations.

The present study aimed for in vitro-in vivo-in silico simulation studies of experimentally designed (32-factorial) Capmul PG-8-cored, Eudragit RSPO-Lutrol F 127 nanocapsules to ferry felodipine using GastroPlus™. The in silico parameter sensitivity analysis for pharmacokinetic parameters was initially assessed to justify the preparation of felodipine-loaded nanocapsules (FLNs) with enhanced solubility to overcome the bioavailability issues of felodipine. The overall integrated desirability ranged between 0.8187 and 0.9488 for three optimized FLNs when analyzed for mean particle size, zeta potential, encapsulation efficiency, and in vitro dissolution parameters. The morphological evaluation (SEM, TEM, and AFM) demonstrated spherical nanoparticles (200-300 nm). Validated LC-MS/MS analysis demonstrated enhanced relative bioavailability (13.37-fold) of optimized FLN as compared to suspension. The simulated regional absorption of the FLN presented significant absorption from the cecum (26.3%) and ascending colon (20.1%) with overall absorption of 67.4% from the GIT tract. Furthermore, in vitro-in vivo correlation demonstrated the Wagner-Nelson method as the preferred model as compared to mechanistic and numerical deconvolution on the basis of least mean absolute prediction error, least standard error of prediction, least mean absolute error, and maximum correlation coefficient (r 2 = 0.920). The study demonstrated enhanced oral absorption of felodipine-loaded nanocapsules, and GastroPlus™ was found to be an efficient simulation tool for in vitro-in vivo-in silico simulations.

Characterization of Heterogeneity and Spatial Distribution of Phases in Complex Solid Dispersions by Thermal Analysis by Structural Characterization and X-ray Micro Computed Tomography.

PURPOSE: This study investigated the effect of drug-excipient miscibility on the heterogeneity and spatial distribution of phase separation in pharmaceutical solid dispersions at a micron-scale using two novel and complementary characterization techniques, thermal analysis by structural characterization (TASC) and X-ray micro-computed tomography (XµCT) in conjunction with conventional characterization methods. METHOD: Complex dispersions containing felodipine, TPGS, PEG and PEO were prepared using hot melt extrusion-injection moulding. The phase separation behavior of the samples was characterized using TASC and XµCT in conjunction with conventional thermal, microscopic and spectroscopic techniques. The in vitro drug release study was performed to demonstrate the impact of phase separation on dissolution of the dispersions. RESULTS: The conventional characterization results indicated the phase separating nature of the carrier materials in the patches and the presence of crystalline drug in the patches with the highest drug loading (30% w/w). TASC and XµCT where used to provide insight into the spatial configuration of the separate phases. TASC enabled assessment of the increased heterogeneity of the dispersions with increasing the drug loading. XµCT allowed the visualization of the accumulation of phase separated (crystalline) drug clusters at the interface of air pockets in the patches with highest drug loading which led to poor dissolution performance. Semi-quantitative assessment of the phase separated drug clusters in the patches were attempted using XµCT. CONCLUSION: TASC and XµCT can provide unique information regarding the phase separation behavior of solid dispersions which can be closely associated with important product quality indicators such as heterogeneity and microstructure.

Felodipine ß-cyclodextrin complex as an active core for time delayed chronotherapeutic treatment of hypertension.

The present research work deals with the development of a time delayed chronotherapeutic formulation of felodipine (FD) aimed at rapid drug release after a desired lag time in the management of hypertension. The developed system comprises a drug core embedded within a swellable layer and coated with an insoluble, water permeable polymeric system. FD cyclodextrin complex was used as an active core while ethyl cellulose was used as an effective coating layer. Dissolution studies of the complex revealed that there was a 3-fold increase in dissolution of the complex compared to plain FD. This dissolution enhancement and rapid drug release resulted from FD amorphisation, as confirmed by XRD, DSC and SEM studies. FTIR and ¹H NMR studies confirmed the complex formation between FD and cyclodextrin based on the observed hydrogen bond interactions. FD release was adequately adjusted by using a pH independent polymer, i.e., ethyl cellulose, along with dibutyl phthalate as plasticizer. Influence of formulation variables like polymer viscosity, plasticizer concentration, super disintegrant concentration in the swellable layer and percent coating weight gain was investigated to characterize the lag time. Upon permeation of water, the core tablet swelled, resulting in the rupture of the coating layer, followed by rapid drug release. The developed formulation of FD showed a lag time of 5-7 h, which is desirable for chronotherapeutic application.

Felodipine nanodispersions as active core for predictable pulsatile chronotherapeutics using PVP/HPMC blends as coating layer.

In the present study predictable pulsatile chronotherapeutics of felodipine (FELO), which is a poorly-water soluble drug, were prepared in the form of two layered tablets. As active core PVP/FELO nanodispersion was used while as effective coating layer different PVP/HPMC blends were added. From dissolution studies of FELO nanodispersions it was revealed that PVP/FELO 90/10 w/w dispersion is an ideal system for pulsatile formulations since the whole amount of FELO is released within the first 30 min. This dissolution enhancement and fast release was attributed to FELO amorphisation, as was found from XRD and DMTA techniques and the effective particle size reduction. Transmission electron microscopy (TEM) studies revealed that FELO creates amorphous nanodispersions into the PVP matrix while particle sizes are directly dependable upon FELO concentration. Drug particles with sizes lower than 150 nm may be the optimal level for a substantial enhancement of FELO dissolution rate. The time of FELO release initiated by the two-layered tablets was adequately adjusted by using different PVP/HPMC blends as coating layer, which is a swellable and erodible barrier. The delaying time of FELO release is directly depended by HPMC concentration and this correlation was mathematically expressed. The significance of these blends is that they are completely miscible over the entire compositional range, thus forming a new matrix with different physicochemical properties, contrary to the initial polymers.

Triglyceride-based microemulsion for intravenous administration of sparingly soluble substances.

A pharmaceutically acceptable microemulsion system composed of a medium-chain triglyceride (MCT), soybean phosphatidylcholine and poly(ethylene glycol)(660)-12-hydroxystearate (12-HSA-EO15) as amphiphiles, and poly(ethylene glycol) 400 (PEG 400) and ethanol as cosolvents is presented and characterized in terms of phase behavior, microstructure, solubilization capacity and in vivo effects after intravenous administration to conscious rats. At a total concentration of 11.9 wt % of soybean phosphatidylcholine and 12-HSA-EO15, a microemulsion region was formed over a wide range of alpha, where alpha is the weight fraction of MCT/(MCT + water + PEG 400 + ethanol). The microstructure of the microemulsion was of a bicontinuous nature even at high oil concentrations. The mean droplet diameter of the oil-in-water emulsion formed after dilution of microemulsions prepared at different alpha within the one-phase region was between 60 and 200 nm. It was concluded that it is possible to administer up to 0.5 mL/kg of the microemulsion (alpha = 0.5) without producing any significant effect on acid-base balance, blood gases, plasma electrolytes, mean arterial blood pressure (MAP), heart rate (HR), and PQ time (the time between depolarization of atrium and chamber). At a dose of 1.5 mL/kg, a temporary increase in MAP, a decrease in HR, and a prolongation of the PQ time were observed.