Application of Carbopol (R) to controlled release preparations I. Carbopol(R) as a novel coating material

We investigated the application of Carbopol(R) (CP) as a novel coating mate rial prepared with various grades of CP having different degrees of cross-l inking and molecular weights. Viscosity and spray mist size of CP aqueous s olutions at various concentrations of CP were measured. Core tablets contai ning theophylline (TP), as a model drug, were coated with CP at various coa ting ratios. The TP release profile from the CP-coated tablets was studied by the JP13 paddle method. CP tablets were prepared by compressing CP powde r, and the swelling behavior of the CP tablets in JP 1st fluid, purified wa ter, and JP 2nd fluid was observed. The spray mist size of all CP aqueous s olutions was small at a concentration of 1% and below, and drastically incr eased over a concentration of 1%. This result suggests that the appropriate concentration of the CP solution for coating is 1% or below. Sustained rel ease of TP from the CP-coated tablets at a coating ratio of only 3% was obs erved in the JP 1st fluid and purified water, although fast release was obs erved in the JP 2nd fluid. The fast release in the latter fluid may be due to the fact that CP is an acid material. These results suggest that it is f easible to control the drug release by use of an extremely small amount of CP coating and that CP is useful as a novel coating material. (C) 2000 Else vier Science B.V. All rights reserved.