Polysorbate 20 as a drug release regulator in ethyl cellulose film coatings.

Tablet coatings of hydrophobic ethyl cellulose have been made more hydrophilic by the addition of a non-ionic surfactant, polysorbate (Tween) 20, to the film. As its content increased, so did the release of sodium salicylate from the coated tablets. With a certain content of surfactant and specific thickness of the tablet coat, zero order release kinetics were observed. Leaching of the polysorbate 20 occurred from all formulations. Scanning and transmission electron micrographs showed that the structure of the coats consisted of several layers parallel to the tablet surface. Polysorbate 20 was seen as small drops in some coats.