title: A novel in situ forming drug delivery system for controlled parenteral drug delivery.
abstract: The objective of this study was to investigate the in vitro drug (diltiazem hydrochloride and buserelin acetate) release from different in situ forming biodegradable drug delivery systems, namely polymer solutions (in situ implants) and in situ microparticle (ISM) systems. The drug release from ISM systems [poly(d,l-lactide) (PLA) or poly(d,l-lactide-co-glycolide) (PLGA)-solution dispersed into an external oil phase] was investigated as a function of the type of solvent and polymer, polymer concentration and internal polymer phase:external oil phase ratio and was compared to the drug release from in situ implant systems and microparticles prepared by conventional methods (solvent evaporation or film grinding). Upon contact with the release medium, the internal polymer phase of the ISM system solidified and formed microparticles. The initial drug release from ISM systems decreased with increasing polymer concentration and decreasing polymer phase:external oil phase ratio. The type of biocompatible solvent also affected the drug release. It decreased in the rank order DMSO>NMP>2-pyrrolidone. In contrast to the release of the low molecular weight diltiazem hydrochloride, the peptide release (buserelin acetate) was strongly dependent on the polymer degradation/erosion. One advantage of the ISM system when compared to in situ implant systems was the significantly reduced burst effect because of the presence of an external oil phase. ISM systems resulted in drug release profiles comparable to the drug release of microparticles prepared by the solvent evaporation method. Therefore, the ISM systems are an attractive alternative to existing complicated microencapsulation methods.
authors.affiliation: College of Pharmacy, Freie Universität Berlin, Kelchstr. 31, 12169 Berlin, Germany. Heiko@schering.de
authors.forename: H
authors.initials: H
authors.lastname: Kranz
authors.forename: R
authors.initials: R
authors.lastname: Bodmeier
mesh_terms: D002064:Buserelin / Q000008:administration & dosage / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D003692:Delayed-Action Preparations; D004110:Diltiazem / Q000008:administration & dosage / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004337:Drug Carriers; D004339:Drug Compounding; D016503:Drug Delivery Systems; D004343:Drug Implants; D004655:Emulsions; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry*; D008956:Models, Chemical; D008970:Molecular Weight; D010316:Particle Size; D019999:Pharmaceutical Solutions; D011091:Polyesters; D011098:Polyglactin 910 / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D011760:Pyrrolidinones / Q000737:chemistry; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D013678:Technology, Pharmaceutical
chemical_list: D003692:Delayed-Action Preparations; D004337:Drug Carriers; D004343:Drug Implants; D004655:Emulsions; D019999:Pharmaceutical Solutions; D011091:Polyesters; D011108:Polymers; D011760:Pyrrolidinones; D012997:Solvents; D019344:Lactic Acid; D011098:Polyglactin 910; C033616:poly(lactide); D004110:Diltiazem; C038678:N-methylpyrrolidone; C028537:2-pyrrolidone; D002064:Buserelin; D004121:Dimethyl Sulfoxide