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We studied the release of salbutamol and ketoprofen enantiomers from HPMC K100M matrices containing two types of cellulose derivatives: cellulose tris (3,5-dimethylphenylcarbamate) and cellulose tris (2,3-dichlorophenylcarbamate), chiral excipients used as stationary phases for liquid chromatography. These matrices provided an extended release of both drugs. Ketoprofen release from formulations elaborated with cellulose tris (2,3-dichlorophenylcarbamate) was by anomalous transport, because the value of n (release exponent of the diffusion equation) ranged between 0.60-0.68, whereas for all other formulations the value of exponent n ranged from 0.50-0.54. The drug thus diffuses through the matrix and is released following a quasi-Fickian diffusion mechanism (stereoselective process). The matrices preferentially retained R-salbutamol and S-ketoprofen and cellulose tris (3,5-dimethylphenylcarbamate) showed more capacity of chiral discrimination for both drugs than cellulose tris (2,3-dichlorophenylcarbamate). Moreover, we observed that stereoselectivity is dependent on the amount of chiral excipient in the formulation. Diffusion tests confirmed the chiral interaction between drugs and cellulose derivatives observed in the dissolution assays except for matrices elaborated with ketoprofen and cellulose tris (2,3-dichlorophenylcarbamate), where the low stereoselectivity observed with the matrices is due to the presence of HPMC K100M. We conclude that the inclusion of these cellulose derivatives in HPMC matrices does not result in a relevant stereoselectivity with respect to the two drugs studied., (Copyright 2002 Wiley-Liss, Inc.)

New formulations of acrylic bone cement based on methyl methacrylate/1-hydroxypropyl methacrylate (MMA/HPMA) monomers were developed with the purpose of obtaining more ductile materials with reduced polymerization shrinkage. In this way, the ductility of such materials increased, but the introduction of high percentages of the hydrophilic component produced an important decrease in Young's modulus and strength. To ascertain the reason for the deterioration of the tensile parameters, an analysis by scanning electron microscopy of these formulations was carried out; it revealed poor adhesion between the matrix and poly(MMA) beads. We also observed that the polymerization shrinkage increased as the amount of hydrophilic monomer in the formulation decreased, and the 50% (v/v) HPMA modified bone cement compensated for this volume reduction with its water uptake swelling. Measurements taken on the setting time and polymerization exotherm showed a decrease in the former and an increase in the latter, because of the introduction of a more reactive monomer in the bone cement formulation., (Copyright 1999 John Wiley & Sons, Inc.)

4-Dimethylaminobenzyl alcohol (DMOH) and 4-dimethylaminobenzyl methacrylate (DMMO) were used as the activators in the benzoyl peroxide initiated redox polymerization for the preparation of acrylic bone cement based on poly(methylmethacrylate) beads of different particle size. The residual monomer content of the cured cements was about 2 wt %, independent of the redox system used in the polymerization, indicating that the activating effect of the tertiary aromatic amines DMOH or DMMO was sufficient to reach a polymerization conversion similar to that obtained with the benzoyl peroxide (BPO) N,N-dimethyl-4-toluidine (DMT) system. The BPO/DMOH and BPO/DMMO redox systems provided exotherms of decreasing peak temperature and increasing setting time, and the cured materials presented higher average molecular weight and similar glass transition temperatures in comparison with those obtained when DMT was used as the activator. In addition, these activators are three times less toxic than the classical DMT.