Tenoxicam-kollicoat IR binary systems: physicochemical and biological evaluation.
Tenoxicam (TNX) binary systems in Kollicoat IR (KL) matrix were prepared in different drug: polymer ratios using kneading and spray-drying method. The prepared binary systems were characterized for drug dissolution rate, differential scanning calorimetry (DSC), IR spectroscopy and x-ray diffractometry. The results showed that the drug dissolution rate was remarkably enhanced by incorporating it in the KL matrix either by kneading or spray-drying, and the dissolution rate was increased by decreasing the drug weight ratio. The DSc and x-ray studies revealed the presence of TNX in less crystalline or amorphous state in its-KL binary systems. Moreover, the spray-dried TNX-KL system in 1:4 ratio, that exhibited the faster dissolution rate, was formulated in oral disintegrating tablets (ODTs). The data indicated that a fast disintegration and higher drug dissolution rate was achieved in case of the ODTs containing the spray-dried form compared to the ODTS containing untreated drug or the commercial tablet (Epicotil). Also, the drug exhibited significantly (p < 0.01) faster onset of the anti-inflammatory analgesic activities in case of the ODTs containing the spray-dried form, that was superior to that observed with both the commercial tablet product and the ODTS containing untreated drug.
Design and In-Vitro Evaluation of Colon Targeted Prednisolone Solid Dispersion Tablets
In the present investigation an attempt was made to prepare colon targeted enteric coated tablet containing different prednisolone solid dispersion formulations, to prevent ulcerative colitis, improve the patient compliance and reduce the side effects of drug in the gastro intestinal tract (GIT). Solid dispersion is one of the most widely used approaches to enhance the solubility as well as dissolution rate of poorly water soluble drugs. Solid dispersions (SDs) of Prednisolone with D-mannitol, PEG 4000 and Kollicoat IR were prepared and evaluated to deliver Prednisolone to the colon in a pre-solubilized form. The selected formula using drug compatible excipients was compressed into fast disintegrating tablets and then coated with Eudragit S100 (pH-responsive polymer), several variables related to both solid dispersion preparation (carrier type and drug to the carrier ratio) and tablet coating (coat level) were studied to show their effects on drug solubility and dissolution. Different analytical techniques like differential scanning caloremitry (DSC), powder x-ray diffraction (PXRD) and scanning electron microscopy (SEM) were studied to prove the change of drug particle from crystal to amorphous form in SDs. The 1:3 Prednisolone/Kollicoat IR SDs showed the greatest improvement in the dissolution rate. The coating level was critical for determining the duration of the lag phase. Best result was given by the 16% coat (Eudragit S100/ Dibutyl phthalate/ talc). This coating level showed an acceptable lag time for the proposed colonic targeting (5 h) as the selected tablet resisted pre-colonic pH values, followed by an immediate release stage in pH 7.4. The suggested covered (coated) tablets may provide a colonic delivery system for prednisolone with enhanced solubility and bioavailability.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME