title: Oestrone loaded poly(l-lactic acid) microspheres: preparation, evaluation and in vitro release kinetics.
abstract: Poly(l-lactic acid) microspheres containing oestrone were prepared by the solvent evaporation method using methylene chloride as the casting solvent and poly(vinyl alcohol) as the emulsifier. Non-agglomerated microspheres with average diameters of 125-160 microns, containing 3-18 per cent oestrone were prepared successfully using a stirring rate of 650 rpm and a poly(vinyl alcohol) concentration as low as 0.15%. Drug loading decreased with an increase in the relative amounts of methylene chloride or emulsifier. Microspheres with 9 per cent loading released approximately 50 per cent of the drug in the first 12 h and the remainder at a much slower rate over several days. Initial examination revealed that the kinetic data followed both a first-order release pattern and the Higuchi matrix model. Differential rate treatment confirmed the Higuchi matrix model and the release mechanism was determined to be diffusion-controlled.
authors.affiliation: School of Pharmacy, University of Missouri-Kansas City 64110.
authors.forename: B V
authors.initials: BV
authors.lastname: Parikh
authors.forename: S M
authors.initials: SM
authors.lastname: Upadrashta
authors.forename: S H
authors.initials: SH
authors.lastname: Neau
authors.forename: N O
authors.initials: NO
authors.lastname: Nuessle
mesh_terms: D003692:Delayed-Action Preparations; D004058:Diffusion; D004339:Drug Compounding; D004970:Estrone / Q000008:administration & dosage* / Q000493:pharmacokinetics; D007773:Lactates / Q000737:chemistry; D019344:Lactic Acid; D000432:Methanol; D008752:Methylene Chloride; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D008954:Models, Biological; D010316:Particle Size; D011091:Polyesters; D011108:Polymers / Q000737:chemistry; D012995:Solubility; D012997:Solvents
chemical_list: D003692:Delayed-Action Preparations; D007773:Lactates; D011091:Polyesters; D011108:Polymers; D012997:Solvents; D004970:Estrone; D019344:Lactic Acid; C033616:poly(lactide); D008752:Methylene Chloride; D000432:Methanol