Development and characterization of extended release Kollidon SR mini-matrices prepared by hot-melt extrusion

Kollidon^® SR as a drug carrier and two model drugs with two different melting points, ibuprofen and theophylline, were studied by hot-melt extrusion. Powder mixtures containing Kollidon^® SR were extruded using a twin-screw extruder at temperatures 70 and 80 °C for ibuprofen and 80 and 90 °C for theophylline. The glass transition temperature (T_g) and maximum torque were inversely related to ibuprofen concentrations, indicating its plasticizing effect. The results of differential scanning calorimetry (DSC) and X-ray diffraction analysis showed that ibuprofen remained in an amorphous or dissolved state in the extrudates containing drug up to 35%, whereas theophylline was dispersed in the polymer matrix. The increase in amounts of ibuprofen or theophylline in the hot-melt extrudates resulted in the increase in the drug release rates. Theophylline release rate in hot-melt extruded matrices decreased as the extrusion temperature increased. In contrast, a higher processing temperature caused the higher ibuprofen release. This was a clear indication of the plasticizing effect of ibuprofen on Kollidon^® SR and a result from water uptake. Theophylline release rate from hot-melt extrudates decreased with increasing triethyl citrate (TEC) level because of the formation of a denser matrix. By adding of Klucel^® LF as a water-soluble additive to the hot-melt extruded matrices, an increase in ibuprofen and theophylline release rates was obtained.