The invention discloses a
controlled release dosage form comprising a therapeutically effective amount of a pharmaceutically
active agent, illustrated by Acyclovir, that would release in about 12 hours not more than about 90% of the said
active agent in a simulated gastric juice in a first order rate of release in a USP type 1
dissolution test, and not containing a solubilizer or a swelling
enhancer or both, comprising (a) a tablet made from
polymer matrix of at least two
biocompatible polymers, illustrated by Carbopol 974P and
polyethylene oxide, the said pharmaceutically
active agent and pharmaceutically permitted excipients; the said tablet capable of rapid swelling without disintegration in the said simulated gastric juice to a size that shall result in its gastric retention in the
stomach and start
controlled release of the said active agent by starting controlled
erosion as well as
diffusion immediately after coming into contact with the said gastric juice, or (b) microspheres of ungrafted
chitosan or a
chitosan derivative illustrated by thiolated
chitosan and
trimethyl chitosan, or Carbopol incorporating the said active agent, wherein the said pharmaceutically active agent is not a polymeric molecule and after administration in
stomach, the said microspheres adhare to the
gastric mucosa for a long time releasing the active agent in a controlled way.