16 research outputs found
Pharmacokinetics and Metabolism of Antipyrine Entrapped in Small (Diameter <7ÎĽM) Vesicular Systems
Stability-Indicating HPLC Method for Arteether and Application to Nanoparticles of Arteether
Determination of two mebeverine metabolites, mebeverine alcohol and desmethylmebeverine alcohol, in human plasma by a dual stable isotope-based gas chromatographic-mass spectrometric method
The effect of intravenous pretreatment with small liposomes on the pharmacokinetics and metabolism of antipyrine in rabbits
Plasma Indomethacin Assay Using High-Performance Liquid Chromatography-Electrospray-Tandem Mass Spectrometry: Application to Therapeutic Drug Monitoring and Pharmacokinetic Studies
Photoinduced oxidation of a tris(2,2'-bipyridyl)ruthenium(II)-peroxodisulfate chemiluminescence system for the analysis of mebeverine HCl pharmaceutical formulations and biological fluids using a two-chip device
Determination of propranolol concentration in small volume of rat plasma by HPLC with fluorometric detection
Characterization of ciclosporin A loaded poly (D,L lactide-co-glycolide) microspheres using modulated temperature differential scanning calorimetry
The aim of this study was to investigate the physical structure of poly (D,L lactide-co-glycolide) (PLGA) microspheres loaded with ciclosporin A in terms of the amorphous properties of the individual components and the phase separation characteristics of the binary systems. Microspheres were prepared using a standard oil-in-water emulsion technique. The thermal properties of the PLGA, ciclosporin A and loaded spheres were investigated using modulated temperature differential scanning calorimetry (MTDSC) using a TA Instruments MTDSC 2920, with scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and high-performance liquid chromatography used as supportive techniques. MTDSC indicated a glass transition for ciclosporin A in the reversing heat flow signal at 107°C, supported by temperature cycling studies, while XRD showed clear evidence for diffraction peaks, thereby indicating that the material as received is semi-crystalline. The unloaded PLGA spheres showed a glass transition (Tg) at 43°C, with no reduction in Tg being observed on loading the peptide up to 50%, w/w. Similarly, no evidence for diffraction peaks were seen for the drug-loaded systems, although the glass transition corresponding to the peptide was observed for the loaded microspheres, suggesting that the drug is present as a separate amorphous phase. Similarly, SEM studies showed the appearance of distinct “islands” on the surface of the spheres that are suggested to correspond to the drug phase, with the size of the islands increasing with drug loading. Evidence is therefore presented that ciclosporin A may exist in a range of solid states, with the degree of crystallinity being altered by processing. In addition, there appears to be little or no miscibility between the drug and PLGA using the manufacturing protocol employed here. These findings may have implications for the choice of manufacturing protocol, the release of peptide drugs from PLGA microspheres and the chemical and physical stability of such drugs