Characterization of poly(ethylene oxide) as a drug carrier in hot-melt extrusion

Poly(ethylene oxide) (PEO) as a drug carrier in hot-melt extrusion was studied by using a model drug, nifedipine, in a twin-screw extruder. Binary mixtures of PEO and nifedipine have been shown to be amenable to hot-melting at a temperature as low as 70°C, well below nifedipine's melting point (172°C). Hot-stage microscopy provided visual evidence that nifedipine can form a miscible dispersion with PEO at 120°C. Complete loss of nifedipine crystallinity when extrudated at and above 120°C with a drug loading of 20% (w/w) was further confirmed by differential scanning calorimetry (DSC) and X-ray diffraction. Cross-sectional imaging of the extrudates using scanning electron microscopy indicated homogeneous drug distribution inside PEO when the processing temperature was above 120°C. Raman spectroscopy confirmed drug-PEO interactions at a molecular level. Cryo-milled extrudates showed significant improvement in dissolution rate compared to either pure nifedipine or the physical mixture of PEO and nifedipine. A state of supersaturation was achieved after 10-minute release in pH 6.8 phosphate buffer. Finally, stability study demonstrated that the solid dispersion system is chemically stable for at least 3 months under the conditions of both 25°C/60% RH and 40°C/75% RH. Overall, PEO appears to be a promising aid/carrier to solublize poorly soluble drugs through the formation of solid dispersion via hot-melt extrusion, thereby improving dissolution and absorption.