Pseudo-T2 mapping for normalization of T2-weighted prostate MRI

Magnetic Resonance Materials in Physics, Biology and Medicine - Signal intensity normalization is necessary to reduce heterogeneity in T2-weighted (T2W) magnetic resonance imaging (MRI) for...     

The effect of pH,buffer capacity and ionic strength on quetiapine fumarate release from matrix tablets prepared using two different polymeric blends

The objective of this study was to investigate the effect of the different physiological parameters of the gastrointestinal (GI) fluid (pH, buffer capacity, and ionic strength) on the in vitro release of the weakly basic BCS class II drug quetiapine fumarate (QF) from two once-a-day matrix tablet formulations (F1 and F2) developed as potential generic equivalents to Seroquel^® XR. F1 tablets were prepared using blends of high and low viscosity grades of hydroxypropyl methylcellulose (HPMC K4M and K100LV, respectively), while F2 tablets were prepared from HPMC K4M and PEGylated glyceryl behenate (Compritol^® HD5 ATO). The two formulations attained release profiles of QF over 24?h similar to that of Seroquel^® XR using the dissolution medium published by the Food and Drug Administration (FDA). A series of solubility and in vitro dissolution studies was then carried out using media that simulate the gastric and intestinal fluids and cover the physiological pH, buffer capacity and ionic strength range of the GIT. Solubility studies revealed that QF exhibits a typical weak base pH-dependent solubility profile and that the solubility of QF increases with increasing the buffer capacity and ionic strength of the media. The release profiles of QF from F1, F2 and Seroquel^® XR tablets were found to be influenced by the pH, buffer capacity and ionic strength of the dissolution media to varying degrees. Results highlight the importance of studying the physiological variables along the GIT in designing controlled release formulations for more predictive in vitro–in vivo correlations.     

Coordination of cobalt(III), nickel(II), copper(II), palladium(II) and platinum(II) with N-ethyl-N′-(4′-methylthiazol-2′-yl)thiourea (HL)

Coordination complexes of formula [ML₂], [CoL₃], [Pd(HL)Cl₂], [CuLCl(H₂O)] and [CuL₂(H₂O)₂] {L=anion of N-ethyl-N^′-(4^′-methylthiazol-2′-yl)thiourea; M=Pt^II, Pd^II or Ni^II} were prepared and characterized by elemental analyses, magnetic susceptibilities, and by IR, NMR, electronic and mass spectral measurements.     

Preparation and characterization of lovastatin polymeric microparticles by coacervation‐phase separation method for dissolution enhancement

Dissolution rate of lovastatin is slow, only 30% of the oral dose is absorbed, and it undergoes extensive first‐pass extraction resulting in low and variable bioavailability. The objective of this research was to enhance the dissolution rate through preparing polymeric microparticles. Coacervation‐phase separation method through the addition of a non‐solvent was used to prepare polymeric microparticles. The method was optimized through studying effects of the type of solvent, the type of polymer, drug : polymer ratio and concentration of surfactant on particle size, particle size distribution, and in‐vitro drug release. Optimized polymeric microparticles and unprocessed drug were characterized using different techniques (SEM, FTIR, DSC, and PXRD) and their flow properties were evaluated. The optimum microparticles were prepared using ethanol as a solvent, Eudragit^® L 100 as a polymer in a drug:polymer ratio of 1:2 and SDS in a concentration of 0.25%. Characterization techniques indicated a change from the crystalline form to an amorphous form that was molecularly dispersed into the polymer. Flow properties of these microparticles were improved as compared to unprocessed drug. Drug release was enhanced 4‐ to 5‐folds probably due to precipitation of the drug in an amorphous form; wetting enhancement; size reduction and stabilization by polymers and surfactants. In conclusion the selection of proper process parameters enhanced drug release 5 folds. The use of DMSO as a solvent and the preparation of physical mixtures in this research provided a means for controlled or prolonged release. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43277.     

Development and evaluation of a novel dosage form of diltiazem HCl using ethylene vinyl acetate copolymer and sodium starch glycolate (in vitro/in vivo study)

The work aims at developing a CR formulation, with high encapsulation efficiency of diltiazem HCl, suitable for twice daily administration. Microparticles, using EVA copolymer, were prepared by coacervation‐phase separation technique, subjected to controlled extraction and vacuum freeze drying processes to generate and immobilize a non uniform initial drug concentration distribution, and evaluated in vitro and in animals. Effects of increasing initial drug concentration, varying polymer system, increasing porosity, and decreasing tortuosity, varying the size of the microparticles and the pH of the dissolution medium on the release rate were evaluated. The results indicated that the release rate from microparticles was constant (zero‐order) for an appreciable period of time but it was low for twice‐daily administration. It increased with increasing initial drug concentration, varying polymer system, increasing porosity, and decreasing tortuosity, and decreasing the size of the microparticles but the duration of constant release was shorter except for formulations containing 2.00 and 2.25% sodium starch glycolate. 10‐h duration of constant release was achieved and the zero‐order release rate was within the required rate to achieve the desired therapeutic level. The pH of the dissolution medium did not have any effect on the release rate. The results of the in vivo study indicated that in vitro dissolution correlated well with in vivo AUC_0‐10 and that there were no statistically significant differences in AUC_0‐10 and C_max between the new CR formulation and Cardizem® CD. Accordingly, a new CR formulation that delivers diltiazem HCl at a constant rate, suitable for twice daily administration was developed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013