In vitro testing of controlled release theophylline preparations: Theolair, Theograd and Theolin.

Three dissolution methods, i.e. a paddle type, the USP disintegration and a column method, were used to characterize the release from three controlled release theophylline preparations, i.e. Theolair Retard 250, Theolin Retard 300 and Theograd 350. The release profiles proved to be dependent upon agitation intensity and pH or a combination of both, but the sensitivity towards these variables differed markedly between the products tested.