Controlled release dosage forms comprising a pharmaceutically active agent capable of not more than 90% release in 12 hours in a simulated gastric juice in first order release rate USP type 1 dissolution test, comprising (a) a tablet made from polymer matrix of at least two biocompatible polymers, the pharmaceutically active agent and excipients; the tablet capable of rapid swelling without disintegration in simulated gastric juice to a size resulting in gastric retention in the stomach and controlled release of the active agent by controlled erosion and diffusion immediately after coming into contact with the gastric juice, or (b) microspheres of ungrafted chitosan or a chitosan derivative or CARBOPOL® incorporating the active agent which is not a polymeric molecule and after administration in stomach, the microspheres adhere to the gastric mucosa for a long and controlled time release of the active agent.