Insight into the Sorption of 5-Fluorouracil and Methotrexate onto Soil-pH, Ionic Strength, and Co-Contaminant Influence.

Nowadays anticancer drugs (ADs), like other pharmaceuticals, are recognized as new emerging pollutants, meaning that they are not commonly monitored in the environment; however, they have great potential to enter the environment and cause adverse effects there. The current scientific literature highlights the problem of their presence in the aquatic environment by publishing more and more results on their analytics and ecotoxicological evaluation. In order to properly assess the risk associated with the presence of ADs in the environment, it is also necessary to investigate the processes that are important in understanding the environmental fate of these compounds. However, the state of knowledge on mobility of ADs in the environment is still very limited. Therefore, the main aim of our study was to investigate the sorption potential of two anticancer drugs, 5-fluorouracil (5-FU) and methotrexate (MTX), onto different soils. Special attention was paid to the determination of the influence of pH and ionic strength as well as presence of co-contaminants (cadmium (Cd2+) and another pharmaceutical-metoprolol (MET)) on the sorption of 5-FU and MTX onto soil. The obtained distribution coefficient values (Kd) ranged from 2.52 to 6.36 L·kg-1 and from 6.79 to 12.94 L·kg-1 for 5-FU and MTX, respectively. Investigated compounds may be classified as slightly or low mobile in the soil matrix (depending on soil). 5-FU may be recognized as more mobile in comparison to MET. It was proved that presence of other soil contaminants may strongly influence their mobility in soil structures. The investigated co-contaminant (MET) caused around 25-fold increased sorption of 5-FU, whereas diminished sorption of MTX. Moreover, the influence of environmental conditions such as pH and ionic strength on their sorption has been clearly demonstrated.

Calycosin Influences the Metabolism of Five Probe Drugs in Rats.

BACKGROUND: Calycosin (CAL), a type of O-methylated isoflavone extracted from the herb Astralagusmembranaceus (AM), is a bioactive chemical with antioxidative, antiphlogistic and antineoplastic activities commonly used in traditional alternative Chinese medicine. AM has been shown to confer health benefits as an adjuvant in the treatment of a variety of diseases. AIM: The main objective of this study was to determine whether CAL influences the cytochrome P450 (CYP450) system involved in drug metabolism. METHODS: Midazolam, tolbutamide, omeprazole, metoprolol and phenacetin were selected as probe drugs. Rats were randomly divided into three groups, specifically, 5% Carboxymethyl cellulose (CMC) for 8 days (Control), 5% CMC for 7 days + CAL for 1 day (single CAL) and CAL for 8 days (conc CAL), and metabolism of the five probe drugs evaluated using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). RESULTS: No significant differences were observed for omeprazole and midazolam, compared to the control group. T max and t1/2 values of only one probe drug, phenacetin, in the conc CAL group were significantly different from those of the control group (T max h: 0.50±0.00 vs 0.23±0.15; control vs conc CAL). C max of tolbutamide was decreased about two-fold in the conc CAL treatment group (conc vs control: 219.48 vs 429.56, P<0.001). CONCLUSION: Calycosin inhibits the catalytic activities of CYP1A2, CYP2D6 and CYP2C9. Accordingly, we recommend caution, particularly when combining CAL as a modality therapy with drugs metabolized by CYP1A2, CYP2D6 and CYP2C9, to reduce the potential risks of drug accumulation or ineffective treatment.

Assessing Drug Release from Manipulated Abuse Deterrent Formulations.

There is a need to develop in vitro dissolution methods that discriminate for particle size of the manipulated abuse deterrent formulation (ADF) and that can be used for in vivo predictive models since dissolution methods developed for intact formulation might not be suitable for manipulated ones. A vertical diffusion cell (VDC) and United States Pharmacopeia (USP) Apparatus 1, 2, and 4 were evaluated for measuring the dissolution of intact and manipulated metoprolol succinate tablets with abuse deterrent-like properties. These tablets were physically manipulated to produce fine (106-500 µm) and coarse (500-1000 µm) powder samples. The VDC method was not able to discriminate the effect of particle size on drug release with varied stirring rate (200 to 800 rpm), molecular weight cut-off (MWCO, 3-5 kDa to 12-14 kDa) of the diffusion membrane, or composition and ionic strength (0.45% and 0.9%) of receiver medium. Standard and modified USP Apparatus 1 and 2 methods were assessed; however, large variations (RSD > 20%) were observed with USP Apparatus 1 for manipulated product dissolution and floating powder samples caused failure of auto-sampling when using standard USP Apparatus 2. For the USP Apparatus 4 dissolution method, packing configuration (1, 3, 8 layers and blend), ionic strength of dissolution medium (0.017, 0.077, and 0.154 M additional NaCl), and flow rate (4, 8, 16 mL/min) were studied to discriminate the effect of particle size on release. The USP Apparatus 4 dissolution method was optimized by using a packaging configuration of 8 layers with 8 mL/min flow rate which exhibited low variability and complete drug release and it could be used for in vivo predictive models. The dissolution method variables can be optimized for a specific product for desirable reproducibility and discriminatory power when using USP Apparatus 4.

UHPLC-MS/MS assay for simultaneous determination of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin with its active metabolites in human plasma, for population-scale drug-drug interactions studies in people living with HIV.

Thanks to highly active antiretroviral treatments, HIV infection is now considered as a chronic condition. Consequently, people living with HIV (PLWH) live longer and encounter more age-related chronic co-morbidities, notably cardiovascular diseases, leading to polypharmacy. As the management of drug-drug interactions (DDIs) constitutes a key aspect of the care of PLWH, the magnitude of pharmacokinetic DDIs between cardiovascular and anti-HIV drugs needs to be more thoroughly characterized. To that endeavour, an UHPLC-MS/MS bioanalytical method has been developed for the simultaneous determination in human plasma of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin and its active metabolites. Plasma samples were subjected to protein precipitation with methanol, followed by evaporation at room temperature under nitrogen of the supernatant, allowing to attain measurable plasma concentrations down to sub-nanogram per milliliter levels. Stable isotope-labelled analytes were used as internal standards. The five drugs and two metabolites were analyzed using a 6-min liquid chromatographic run coupled to electrospray triple quadrupole mass spectrometry detection. The method was validated over the clinically relevant concentrations ranging from 0.3 to 480 ng/mL for amlodipine, atorvastatin and p-OH-atorvastatin, and 0.4 to 480 ng/mL for pravastatin, 0.5 to 480 ng/mL for rosuvastatin and o-OH-atorvastatin, and 3 to 4800 ng/mL for metoprolol. Validation performances such as trueness (95.4-110.8%), repeatability (1.5-13.4%) and intermediate precision (3.6-14.5%) were in agreement with current international recommendations. Accuracy profiles (total error approach) were lying within the limits of ±30% accepted in bioanalysis. This rapid and robust UHPLC-MS/MS assay allows the simultaneous quantification in plasma of the major currently used cardiovascular drugs and offers an efficient analytical tool for clinical pharmacokinetics as well as DDIs studies.

Metal organic framework HKUST-1 modified with carboxymethyl-ß-cyclodextrin for use in improved open tubular capillary electrochromatographic enantioseparation of five basic drugs.

This work shows that the metal organic framework (MOF) HKUST-1 of type Cu3(BTC)2 (also referred to as MOF-199; a face-centered-cubic MOF containing nanochannels) is a most viable coating for use in enantioseparation in capillary electrochromatography (CEC). A HKUST-1 modified capillary was prepared and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, elemental analysis and thermogravimetric analysis. CEC-based enantioseparation of the basic drugs propranolol (PRO), esmolol (ESM), metoprolol (MET), amlodipine (AML) and sotalol (SOT) was performed by using carboxymethyl-ß-cyclodextrin as the chiral selector. Compared with a fused-silica capillary, the resolutions are improved (ESM: 1.79; MET: 1.80; PRO: 4.35; SOT: 1.91; AML: 2.65). The concentration of chiral selector, buffer pH value, applied voltage and buffer concentration were optimized, and the reproducibilities of the migration times and Rs values were evaluated. Graphical abstract Schematic presentation of the preparation of a HKUST-1@capillary for enantioseparation of racemic drugs. Cu(NO3)2 and 1,3,5-benzenetricarboxylic acid (BTC) were utilized to prepare the HKUST-1@capillary. Then the capillary was applied to construct capillary electrochromatography system with carboxymethyl-ß-cyclodextrin (CM-ß-CD) for separation of basic racemic drugs.

The Influence of Fatty Acids on Metoprolol - Human Serum Albumin Interaction in Low Affinity Binding Sites: A Multifactorial NMR Approach.

BACKGROUND: Metoprolol (MTP) is a cardio-selective ß1-blocker used in hypertension, angina pectoris and chronic heart failure therapies. Serum albumin is the most frequently occurring protein in blood plasma. The binding of ligands to human serum albumin (HSA) has an important effect on pharmacokinetics and final clinical effects. OBJECTIVE: The objectives of this study included a detailed analysis of metoprolol - serum albumin interactions in low affinity binding sites, on the surface or within the hydrophobic subdomain of a macromolecule, as well as an analysis of the competition between MTP and fatty acids in binding with protein. METHODS: The analysis of the drug-albumin interaction was based on the observed chemical shifts in combination with correlation Times (T1 -1 = τ) [1/s], 2D NOESY 1H NMR spectra and association constants Ka [M-1]. For the determination of chemical shifts σ [ppm], relaxation times T1 [s] and for the NOESY experiment, the final concentrations of MTP and albumins (in the presence (HSA) and absence of fatty acids (dHSA)) were 5 x 10-3 M and 2 x 10-5 M - 4.55 x 10-4 M, respectively. In order to calculate the association constants, the final concentrations of MTP and both HSA and dHSA were 2.75 x 10-3 M - 6.25 x 10-2 M and 2.5 x 10-4 M, respectively. For the analysis, the MTP proton resonances of aliphatic H17, aromatic (H2/H6 and H3/H5) and the methoxy group H14 were chosen. RESULTS: Changes in the values of the 1H NMR chemical shift [ppm] are evidence of interaction between MTP, fatted (HSA) and defatted (dHSA) human serum albumin. With an increase of albumin concentration, changes in the chemical shift values were observed for the aromatic protons H2/H6 (Δσ = 0.013 ppm and 0.018 ppm) and H3/H5 (Δσ = 0.015 ppm and 0.019 ppm), the aliphatic proton H17 (Δσ = 0.018 ppm and 0.022 ppm) and the aliphatic protons of the methoxy group H14 (Δσ = 0.019 ppm and 0.022 ppm) for dHSA and HSA, respectively. Greater changes in chemical shifts in the presence of fatty acids (FA) were observed. Changes in the correlation times of MTP aromatic H2/H6 (Δτc = 0.224 1/s and 0.189 1/s) and H3/H5 (Δτc = 0.269 1/s and 0.210 1/s), aliphatic from the methoxy group H14 (Δτc = 0.472 1/s and 0.271 1/s) and aliphatic H17 protons (Δτc = 0.178 1/s and 0.137 1/s) for dHSA and HSA systems, respectively. It confirms the interaction between the drug and albumin are evidence for the dynamics of the process. In the presence of FA the relaxation time of all analyzed MTP proton resonance signals significantly increases (due to the decrease of correlation time). This phenomenon is due to the increase of electron density in the MTP protons' surroundings. Association constants for the MTP-dHSA complex in the low affinity site range between 0.29 x 102 M-1 and 0.47 x 102 M-1. The presence of FA results in a two to three-fold increase of the Ka values of protons from aromatic (H2/H6 and H3/H5), aliphatic H17 and methoxy (H14) groups. In 2D NOESY spectra proton magnetization transfer was observed between cysteine (Cys-34) and aromatic H3/H5 and H2/H6 protons. Cross-peaks were also observed between cysteine and aliphatic protons from the methoxy group. CONCLUSION: The selective changes in σ [ppm] and τc [1/s] values indicated the unequal participation of chemical groups of MTP in the interaction with HSA and dHSA. The data obtained suggest that the presence of fatty acids increases the accessibility of low affinity sites of serum albumin to MTP, which results in the higher affinity of albumin towards the drug. The results showed that the main binding site of MTP and fatty acid is probably a low affinity site in subdomain IB, where Cys-34 can be located.

Development of metoprolol tartrate-loaded sustained-release pellets: effect of talc on the mechanism of drug release.

Talc is one of the most commonly used antiadherents in the coating film. However, the mechanism of influence of talc on drug release has yet to be fully understood. In this study, metoprolol tartrate (MT)-loaded Eudragit NE 30 D-coated sustained-release (SR) pellets were prepared using talc as an antiadherent in the layering and coating processes. Talc significantly reduced the stickiness of the layered or coated substrates, thus enhancing the process smoothness. Moreover, the incorporation of talc into the coating film significantly affected drug release. The water vapor permeability and drug permeability of free films increased as the concentration of talc increased. Importantly, talc had a dynamic effect on the drug release. The drug release rate of the pellets in the initial stage (within 2 h) increased with increasing talc concentrations, which exceeded the critical pigment volume concentration resulted in leaks formation in the coated film. However, subsequent swelling of the membrane and expansion of the copolymer network eliminated the influence of talc and the drug release was then controlled by the polymeric membrane. These results suggest that talc contributed to the reduction of the sticking of layered or coated substrates, and facilitated the manufacturing process and drug release properties.

Preparation and characterization of metoprolol tartrate containing matrix type transdermal drug delivery system.

The present study aimed to develop matrix-type transdermal drug delivery system (TDDS) of metoprolol tartrate using polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA). The transdermal films were evaluated for physical parameters, Fourier transform infrared spectroscopy analysis (FTIR), differential scanning calorimetry (DSC), in vitro drug release, in vitro skin permeability, skin irritation test and stability studies. The films were found to be tough, non-sticky, easily moldable and possess good tensile strength. As the concentration of PVA was increased, the tensile strength of the films was also increased. Results of FTIR spectroscopy and DSC revealed the absence of any drug-polymer interactions. In vitro release of metoprolol followed zero-order kinetics and the mechanism of release was found to be diffusion rate controlled. In vitro release studies of metoprolol using Keshary-Chein (vertical diffusion cell) indicated 65.5 % drug was released in 24 h. In vitro skin permeation of metoprolol transdermal films showed 58.13 % of the drug was released after 24 h. In vitro skin permeation of metoprolol followed zero-order kinetics in selected formulations. The mechanism of release was found to be diffusion rate controlled. In a 22-day skin irritation test, tested formulation of transdermal films did not exhibit any allergic reactions, inflammation, or contact dermatitis. The transdermal films showed good stability in the 180-day stability study. It can be concluded that the TDDS of MPT can help in bypassing the first-pass effect and will provide patient improved compliance, without sacrificing the therapeutic advantages of the drugs.

Formulation development and comparative in vitro study of metoprolol tartrate (IR) tablets.

The objective of the present work was to develop Immediate Release (IR) tablets of Metoprolol Tartrate (MT) and to compare trial formulations to a reference product. Six formulations (F1-F6) were designed using central composite method and compared to a reference brand (A). Two marketed products (brands B and C) were also evaluated. F1-F6 were prepared with Avicel PH101 (filler), Crospovidone (disintegrant) and Magnesium Stearate (lubricant) by direct compression. Pharmacopoeial and non-pharmacopoeial methods were used to assess their quality. Furthermore, drug profiles were characterized using model dependent and independent (f(2)) approaches. Brands B and C and F5 and F6 did not qualify the tests for content uniformity. Moreover, brand B did not meet weight variation criteria and brand C did not satisfy requirements for single point dissolution test. Of the trial formulations, F2 failed the test for uniformity in thickness while F4 did not disintegrate within time limit. Only F1 and F3 met all quality parameters and were subjected to accelerated stability testing without significant alterations in their physicochemical characteristics. Based on AIC and r(2)(adjusted) values obtained by applying various kinetic models, drug release was determined to most closely follow Hixson-Crowell cube root law. F1 was determined to be the optimized formulation.

Biopharmaceutic Risk Assessment of Brand and Generic Lamotrigine Tablets.

The therapeutic equivalence of generic and brand name antiepileptic drugs has been questioned by neurologists and the epilepsy community. A potential contributor to such concerns is pharmaceutical quality. The objective was to assess the biopharmaceutic risk of brand name Lamictal 100 mg tablets and generic lamotrigine 100 mg tablets from several manufacturers. Lamotrigine was characterized in terms of the Biopharmaceutics Classification System (BCS), including aqueous solubility and Caco-2 permeability. A panel of pharmaceutical quality tests was also performed on three batches of Lamictal, three batches of Teva generic, and one batch of each of four other generics: appearance, identity, assay, impurity, uniformity of dosage units, disintegration, dissolution, friability, and loss on drying. These market surveillance results indicate that all brand name and generic lamotrigine 100 mg tablets passed all tests and showed acceptable pharmaceutical quality and low biopharmaceutic risk. Lamotrigine was classified as a BCS class IIb drug, exhibiting pH-dependent aqueous solubility and dissolution. At pH 1.2 and 4.5, lamotrigine exhibited high solubility, whereas lamotrigine exhibited low solubility at pH 6.8, including non-sink dissolution. Lamotrigine showed high Caco-2 permeability. The apparent permeability (Papp) of lamotrigine was (73.7 ± 8.7) × 10(-6) cm/s in the apical-to-basolateral (AP-BL) direction and (41.4 ± 1.6) × 10(-6) cm/s in the BL-AP direction, which were higher than metoprolol's AP-BL Papp of (21.2 ± 0.9) × 10(-6) cm/s and BL-AP Papp of (34.6 ± 4.6) × 10(-6) cm/s. Overall, lamotrigine's favorable biopharmaceutics from a drug substance perspective and favorable quality characteristics from a tablet formulation perspective suggest that multisource lamotrigine tablets exhibit a low biopharmaceutic risk.

Toxicity assessment of metoprolol and its photodegradation mixtures obtained by using different type of TiO2 catalysts in the mammalian cell lines.

Toxicity of metoprolol (MET) alone and in mixtures with its photocatalytic degradation intermediates obtained by using TiO2 Wackherr and Degussa P25 under UV irradiation in the presence of O2 was evaluated in vitro in a panel of three histologically different cell lines: rat hepatoma (H-4-II-E), human colon adenocarcinoma (HT-29) and human fetal lung (MRC-5). Both catalysts promoted a time-dependent increase in the toxicity of the photodegradation products, and those obtained using Degussa P25 photocatalyst were more toxic. The most pronounced and selective toxic action of MET and products of its photodegradation was observed in the hepatic cell line. The higher toxicity of the mixtures obtained using Degussa P25 catalyst could be explained by a different mechanism of MET degradation, i.e. by the presence or higher concentrations of some intermediates. Although the concentrations of intermediates obtained using TiO2 Wackherr catalyst were higher, they did not affect significantly the growth of the examined cell lines, indicating their lower toxicity. This suggests that a treatment aiming at complete mineralization should be performed bearing in mind that the type of catalyst, the concentration of target molecule, and the duration of the process are significant factors that determine the nature and toxicity of the resulting mixtures. Although the EC50 values of MET obtained in mammalian cell lines were higher compared to the bioassays for lower trophic levels, the time-dependent promotion of toxicity of degradation mixtures should be attributed to the higher sensitivity of mammalian cell bioassays.

Upscaling and in-line process monitoring via spectroscopic techniques of ethylene vinyl acetate hot-melt extruded formulations.

The aim of the present work was to evaluate drug release and quality of EVA/drug matrices at different PEO 7M concentrations (5 and 15%), manufactured using two different hot-melt extruders: a lab-scale mini extruder and a pilot-scale extruder. The process parameters used on both extruders (temperature and screw speed) and drug release from the matrices were compared. On the lab-scale extruder all formulations were extruded at 90 °C, whereas on the pilot-scale extruder the temperature of the die was adjusted to 100 °C in order to achieve a constant pressure at the extrusion die, hence constant material flow through the die to yield smooth extrudates. Screw speed was also adjusted from 60 rpm (lab-scale extruder) to 90 rpm (pilot-scale extruder) in order to obtain a balance between feeding rate and screw speed. Drug release from the obtained matrices on both extruders was also assessed. Despite the differences in diameter (diameter of 2 and 3mm for the lab-scale extruder and pilot-scale extruder, respectively), temperature and screw speed, drug release per surface area was similar. DSC analysis of a formulation [EVA40/MPT (50/50, w/w) with 5% PEO] indicated small changes in its solid state after extrusion on both extruders: drug crystallinity was reduced by max. 20%, PEO recrystallized after cooling and EVA remained semi-crystalline. Extrusion experiments on the pilot-scale extruder of EVA/MPT, 50/50 (w/w) formulations were also monitored in-line using Raman and NIR spectroscopy in order to evaluate the material behavior at a molecular level in the extrusion barrel as function of the process settings (extrusion temperature: 90, 110 and 140 °C; screw speed: 90 and 110 rpm). At 90 and 110 °C the crystallinity of the drug was reduced, but the majority of MPT remained in its crystalline state as specific peaks in the Raman spectra of the drug became broader. These differences were accentuated when extrusion was performed at 140 °C as the drug completely melted. Peak shifts to lower frequencies [(CO) groups of the drug and (CH(3)COO) groups of EVA] were registered at all extrusion temperatures, with maximum effect at 140 °C indicating molecular interactions. Increasing the screw speed did not result in peak shifts of Raman spectra. NIR confirmed these observations and showed an additional peak in the spectra characteristic of (OH) bounds.

Sustained release from hot-melt extruded matrices based on ethylene vinyl acetate and polyethylene oxide.

The aim of the present study was to evaluate the importance of matrix flexibility of hot-melt extruded (HME) ethylene vinyl acetate (EVA) matrices (with vinyl acetate (VA) contents of 9%, 15%, 28% and 40%), through the addition of hydrophilic polymers with distinct swelling capacity. Polyethylene oxide (PEO 100K, 1M and 7M) was used as swelling agent and metoprolol tartrate (MPT) as model drug. The processability via HME and drug release profiles of EVA/MPT/PEO formulations were assessed. Solid state characteristics, porosity and polymer miscibility of EVA/PEO matrices were evaluated by means of DSC, X-ray tomography and Raman spectroscopy. The processability via HME varied according to the VA content: EVA 40 and 28 were extruded at 90°C, whereas higher viscosity EVA grades (EVA 15 and 9) required a minimum extrusion temperature of 110°C to obtain high-quality extrudates. Drug release from EVA matrices depended on the VA content, PEO molecular weight and PEO content, matrix porosity as well as pore size distribution. Interestingly, the interplay of PEO leaching, matrix swelling, water influx and changes in matrix porosity influenced drug release: EVA 40- and 28-based matrices extruded with PEO of higher MW accelerated drug release, whereas for EVA 15- and 9-based matrices, drug release slowed down. These differences were related to the distinct polymer flexibility imposed by the VA content (lower VA content presents higher crystallinity and less free movement of the amorphous segments resulting in a higher rigidity). In all cases, diffusional mass transport seems to play a major role, as demonstrated by mathematical modeling using an analytical solution of Fick's second law. The bioavailability of EVA 40 and 28 matrices in dogs was not significantly different, independent of PEO 7M concentration.

In-line NIR spectroscopy for the understanding of polymer-drug interaction during pharmaceutical hot-melt extrusion.

The aim was to evaluate near-infrared spectroscopy for the in-line determination of the drug concentration, the polymer-drug solid-state behaviour and molecular interactions during hot-melt extrusion. Kollidon® SR was extruded with varying metoprolol tartrate (MPT) concentrations (20%, 30% and 40%) and monitored using NIR spectroscopy. A PLS model allowed drug concentration determination. The correlation between predicted and real MPT concentrations was good (R(2)=0.97). The predictive performance of the model was evaluated by the root mean square error of prediction, which was 1.54%. Kollidon® SR with 40% MPT was extruded at 105°C and 135°C to evaluate NIR spectroscopy for in-line polymer-drug solid-state characterisation. NIR spectra indicated the presence of amorphous MPT and hydrogen bonds between drug and polymer in the extrudates. More amorphous MPT and interactions could be found in the extrudates produced at 135°C than at 105°C. Raman spectroscopy, DSC and ATR FT-IR were used to confirm the NIR observations. Due to the instability of the formulation, only in-line Raman spectroscopy was an adequate confirmation tool. NIR spectroscopy is a potential PAT-tool for the in-line determination of API concentration and for the polymer-drug solid-state behaviour monitoring during pharmaceutical hot-melt extrusion.

Pharmacophore modeling for hERG channel facilitation.

Human ether-a-go-go-related gene (hERG) channels play a critical role in cardiac action potential repolarization. The unintended block of hERG channels by compounds can prolong the cardiac action potential duration and induce arrhythmia. Several compounds not only block hERG channels but also enhance channel activation after the application of a depolarizing voltage step. This is referred to as facilitation. In this study, we tried to extract the property of compounds that induce hERG channel facilitation. We first examined the facilitation effects of structurally diverse hERG channel blockers in Xenopus oocytes. Ten of 13 assayed compounds allowed facilitation, suggesting that it is an effect common to most hERG channel blockers. We constructed a pharmacophore model for hERG channel facilitation. The model consisted of one positively ionizable feature and three hydrophobic features. Verification experiments suggest that the model well describes the structure-activity relationship for facilitation. Comparison of the pharmacophore for facilitation with that for hERG channel block showed that the spatial arrangement of features is clearly different. It is therefore conceivable that two different interactions of a compound with hERG channels exert two pharmacological effects, block and facilitation.

Prediction of a new surface binding pocket and evaluation of inhibitors against huntingtin interacting protein 14: an insight using docking studies.

Protein-protein interactions play an important role in regulating the expression of huntingtin protein (htt). Expansion of polyglutamine tracts in htt results in neurodegenerative Huntington disease. Huntingtin interacting protein (HIP14) is an important interacting partner of htt and the altered interactions have been proposed to play an important role in disease progression. In the present study, an attempt has been made to explore the potential of several known Huntington inhibitors to inhibit HIP14. The docking studies have resulted in the identification of a novel binding site for these inhibitors distinct from the previously known ankyrin repeat domain. The results have been validated using geometry based docking transformations against the other binding pocket. The specificity of binding has been determined with high values of both accuracy and precision. Nine potential inhibitors obtained after screening belong to three distinct classes of compounds viz, carbohydrates (deoxy-glucose), alcohols (including phenolic scaffold) and tetracycline. The compounds form stable complex with protein exhibiting optimal intermolecular and Gibbs free energy. The hydrogen bonding and hydrophobic interactions predominantly contribute to the stability of these complexes. The present study identifies metoprolol, minocyclines and 18 F fluorodeoxyglucose as the best inhibitors that bind specifically to the new site. Therefore, these compounds can further be exploited for their potential to serve in the diagnosis and treatment of Huntington disease. The quantitative predictions provide a scope for experimental testing in future.

Chitosan in situ gelation for improved drug loading and retention in poloxamer 407 gels.

A method for the in situ gelation of poloxamers and the mucoadhesive polymer chitosan has been developed by exploiting the tendency of poloxamer solution to form gel at physiological temperatures and of chitosan (CT) to form ionotropic gel structures in the presence of sodium tripolyphosphate (TPP). Novel poloxamer gels containing CT-TPP complex formed in situ during the administration were prepared by mixing poloxamer-CT and poloxamer-TPP solutions in double syringes. The micellization and gelation of poloxamer 407 in the presence of chitosan and/or TPP were studied using differential scanning calorimetry and tube inversion; both additives were found to reduce the critical micellization temperature and critical gelation temperature of poloxamer aqueous solution. The poloxamer gels containing CT-TPP complex formed in situ were found to exhibit reduced dissolution rate and superior release characteristics with three different drugs--metoprolol, doxycycline and flufenamic acid. Furthermore, by varying the compositions of the two solutions independently, it is possible to control the pH in a way to suit the solubilization of a drug as well as the specific environment of a particular application site. By varying the concentrations of chitosan, TPP and poloxamer, the delivery system can be fine-tuned to afford gels with specific properties, ranging from nanoparticle suspensions to semisolid gels. These in situ gels have the potential to increase the utility of thermo-reversible poloxamers in drug delivery.

Ethylene vinyl acetate as matrix for oral sustained release dosage forms produced via hot-melt extrusion.

Different ethylene vinyl acetate grades (EVA9, EVA15, EVA28 and EVA40 having a VA content of 9%, 15%, 28% and 40%, respectively) were characterized via differential scanning calorimetry. Glass transition temperature (T(g)), polymer crystallinity, melting point and polymer flexibility were positively influenced by the vinyl acetate content. The processability of EVA-based formulations produced by means of hot-melt extrusion (2mm die) was evaluated in function of VA content, extrusion temperature (60-140°C) and metoprolol tartrate (MPT, used as model drug) concentration (10-60%). Matrices containing 50% MPT resulted in smooth-surfaced extrudates, whereas at 60% drug content severe surface defects (shark skinning) were observed. Drug release from EVA/MPT matrices (50/50, w/w) was affected by the EVA grades: 90% after 24h for EVA15 and 28, while EVA9 and EVA40 formulations released 80% and 60%, respectively. Drug release also depended on drug loading and extrusion temperature. For all systems, the total matrix porosity (measured by X-ray tomography) was decreased after dissolution due to elastic rearrangement of the polymer. However, the largest porosity reduction was observed for EVA40 matrices as partial melting of the structure (melt onset temperature: 34.7°C) also contributed (thereby reducing the drug release pathway and yielding the lowest release rate from EVA40 formulations). The Simulator of the Human Intestinal Microbial Ecosystem (SHIME) used to evaluate the stability of EVA during gastrointestinal transit showed that EVA was not modified during GI transit, nor did it affect the GI ecosystem following oral administration.

Lack of a primary physicochemical determinant in the direct transport of drugs to the brain after nasal administration in rats: potential involvement of transporters in the pathway.

The objectives of this study were to evaluate the relative contribution of the direct pathway in overall brain transport for 17 model drugs with different physicochemical properties after nasal administrations and to identify factors that govern the fraction of the dose transported to the brain via the direct pathway (F(a, direct)). When the model drugs were nasally administered to rats, 5 of the 17 model drugs were delivered to a significant extent to the brain via the direct pathway. Multiple linear regression analyses showed that the correlation between various physicochemical properties and F(a, direct) was not statistically significant, indicative of a lack of primary physicochemical determinants in the direct transport pathway. Transporters such as rOAT3 and rOCT2 were expressed at significant levels in rat olfactory epithelia, and uptakes of standard substrates were significantly decreased in HEK293 cells expressing rOAT3 and rOCT2 in the presence of the five model drugs that were delivered to appreciable extents to the brain via the direct pathway. Therefore, these observations indicate that carrier-mediated transport may play a role in the brain delivery of drugs from the nose via the direct transport pathway.

UV-C radiation based methods for aqueous metoprolol elimination.

The endocrine disruptor metoprolol has been oxidised in aqueous solution by means of the systems UV-C, UV-C/H(2)O(2), UV-C/percarbonate, UV-C/monopersulfate, UV-C/TiO(2), UV-C/H(2)O(2)/TiO(2) and photo-Fenton. From simple photolysis experiments the quantum yield of metoprolol has been calculated (roughly 5x10(-3) mol Einstein(-1) at circumneutral pH). Addition of free radicals promoters significantly enhanced the metoprolol depletion rate. Mineralization degree was negligible when no promoter was added, while low values were achieved in the presence of either inorganic peroxides or titanium dioxide. The combination of radiation, hydrogen peroxide and TiO(2) increased the mineralization level up to values in the proximity of 45-50% under the best conditions investigated. The photo-Fenton process was the best system in terms of total oxidation (mineralization degree 70%) when optimum conditions were applied.