Poly(methylglyoxylate), a biodegradable polymeric material for new drug delivery systems

A biodegradable hydrophobic matrix, poly(methylglyoxylate) and a water-soluble drug, metoprolol, were used to prepare solid dispersions in order to obtain an oral controlled drug delivery system. Preliminary thermal and chemical studies of the polymer revealed sufficient properties to undergo the preparation of solid dispersions as well as satisfactory behaviour in acidic or alkaline medium. Consequently, a first series of co-melts and co-precipitates containing various drug concentrations (75, 50, 35 and 25%, w/w) were prepared with a granulometry varying between 250 and 100 mu m. DSC studies showed a better dispersion of the drug in the matrix for co-precipitates than for co-melts. In vitro dissolution kinetic studies showed an important burst effect during the first 30 min. Then a very slow release of the drug was observed during the last 7.5 h. A second series of co-precipitates with lower drug content (25, 15 and 5%, w/w) and lower granulometry (up to 100 pm) was tested. Finally, a dissolution profile similar to those of a commercial Seloken 200 LP tablet formulation was obtained, for a 15% (w/w) drug concentration in the polymer matrix and for a solid dispersion prepared by solvent method. (C) 1998 Elsevier Science B.V. All rights reserved.