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SELECTIVE COATING OF CYLINDRICAL MATRICES WITH A CENTRAL HOLE .1. AN INTERPRETATION OF THE SWELLING PROCESS
No full textCylindrical matrices were prepared by compression either of polyvinyl alcohol 100000 or mixtures of the excipient and a drug (sodium salicylate or theophylline). To modify the cylindrical shape, a hole was bored in the centre of the flat surface through both sides of the matrices. Different swellable systems were obtained applying an impermeable coating to one, two or three surfaces of the perforated matrices. The swelling of the perforated matrices was modified according to the number and the position of the coated surfaces (selective coating) and the loaded drug. Pseudo-zero order kinetics were obtained when the interior hole was the only uncoated surface
ANALYSIS OF RELEASE DATA IN THE EVALUATION OF THE PHYSICAL STATE OF PROGESTERONE IN MATRIX SYSTEMS
No full textEthylene-vinyl acetate microspheres were prepared by an emulsion solvent-evaporation method as sustained delivery carriers of progesterone. Physical state of the drug in the microspheres was affected by drug loading level. As thermal analysis and mathematical release models showed, low payloads of the matrix supported the molecularly dispersed drug. Crystalline drug appeared only as the drug loading level increased. The release process of the crystalline drug produced a porosity increase in the polymeric system; thus, the drug could diffuse through pores and channels. Hence, the porosity of the matrix structure was affected by the payload. This hypothesis could justify the increasing goodness-of-fit of the release data to the square-root model as the drug loading level of the microspheres increase
In vitro absorption of drugs using the Sartorius apparatus according to Stricker: salicylic acid. II
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Application of perforated geometry for the development of a drug release system with differential speed
No full textUse of solid dispersions with PVP for controlled release of furosemide by continuous intragastric infusions
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