1996 年 44 巻 4 号 p. 837-842
Acrylic polymer (Eudragit-RS 100 or -RS PM) microspheres of acebutolol hydrochloride, a highly water soluble model drug, were prepared by the polymeric shpherical crystallization technique with a good slvent (acetone + ethanol), a bridging liquid (water) and a poor slvent (cyclohexane) system. The microspheres were produced through coacervation of the drug and polymer in quasi-emulsion droplets of the good solvent and the birdging liquid mixture, but were dissolved when dispersed in the poor solvent. The preparation mechanism and the ratios of solvents employed for inducing the coacervation were determined by constructing a solubility phase diagarm of the polymer in the good and poor solvent systems. To improve the sustained releasing properties of the microspheres, they were coated directly with sodium alginate powder in the same preparation batch of microspheres. The treatments of the microspheres and coated microspheres with triethyl citrate significantly retarded the drug release rates from each due to the improved embedding of the drug in the polymer. Whewn they were formulated into capsules or tablets, the drug release rates were prolonged much further because of their gelled matrix structures formed during dissolution. The drug release mechanism was described by the square root time model by the diffusion of drug through the gelled layer of polymer.
