Patent ID: 8512748

Claim:
A pharmaceutical controlled release system for administration of active substances with pH-dependent solubilities, comprising: a) a core material comprising one or more pharmaceutically acceptable pH modifiers, wherein at least one pharmaceutically acceptable pH modifier is an organic acid; b) a first insulating layer, provided on the core material, comprising one or more pharmaceutically acceptable water soluble polymers; c) a second layer comprising a pharmaceutically acceptable water-insoluble (poly(ethyl acrylate/methyl methacrylate/trimethylammonioethyl methacrylate chloride)polymer having either a 1:2:0.1 or 1:2:0.2 ratio of ethyl acrylate to methyl methacrylate to trimethylammonioethyl methacrylate chloride monomers; d) a third layer comprising at least one active substance having a pH-dependent solubility; e) a fourth layer comprising one or more pharmaceutically acceptable polymers having anionic or no ionic groups; and f) optionally a fifth layer.