Drug release from perforated matrices containing hydroxypropylcellulose

Perforated matrices were obtained using as excipient hydroxypropylcelluloses having different viscosity degrees. Furosemide release was affected by the polymer viscosity, while it was not related to the releasing surface area. In fact, the matrix having the highest hole diameter, and consequently the lowest releasing surface area, showed the highest release rate. The application of an impermeable coating on all the surfaces, except the hole surface, restricted the releasing surface area reducing the release rate. Furosemide release from the perforated coated matrices was the same regardless of the hole diameter (surface) as the data were related to the unitary releasing surface. The comparative analysis of the drug release mechanism showed the decrease of the erosion (polymer dissolution) component and the increase of the drug diffusion component of the process as the perforated matrices were coated. These results can be justified by the restriction of the matrix swelling produced by the impermeable coating. (C) 1998 Elsevier Science B.V. All rights reserved.