Galenical development of a new sustained-release theophylline pellet formulation for once-daily administration.

Euphylong is a sustained-release product consisting of encapsulated pellets covered with a porous membrane. Since the mechanism of release is osmotic, this new formulation has been termed a "micro-osmotic system". The course of theophylline release is linear over a wide range and is independent of pH value, surface tension and buffer concentration of the dissolution medium. Furthermore, the in-vitro release remains largely uninfluenced by the dissolution model used and by agitation of the dissolution medium. Variations in the in-vitro release profiles produce variations in the in-vivo absorption profiles determined by deconvolution. It is therefore possible, irrespective of the dissolution model and medium used, to produce in-vitro release profiles that enable in-vivo absorption to be predicted by varying the thickness or porosity of the membrane.