<Li> The matrix device has the drug in a matrix and the matrix is dissolved instead of a coating . It can come either as drug impregnated spheres or drug impregnated tablets . </Li> <P> Osmotic controlled - release oral delivery systems (OROS) have the form of a rigid tablet with a semi-permeable outer membrane and one or more small laser drilled holes in it . As the tablet passes through the body, water is absorbed through the semipermeable membrane via osmosis, and the resulting osmotic pressure is used to push the active drug through the opening (s) in the tablet . OROS is a trademarked name owned by ALZA Corporation, which pioneered the use of osmotic pumps for oral drug delivery . </P> <P> Osmotic release systems have a number of major advantages over other controlled - release mechanisms . They are significantly less affected by factors such as pH, food intake, GI motility, and differing intestinal environments . Using an osmotic pump to deliver drugs has additional inherent advantages regarding control over drug delivery rates . This allows for much more precise drug delivery over an extended period of time, which results in much more predictable pharmacokinetics . However, osmotic release systems are relatively complicated, somewhat difficult to manufacture, and may cause irritation or even blockage of the GI tract due to prolonged release of irritating drugs from the non-deformable tablet . </P> <P> In the ion - exchange method, the resins are cross-linked water - insoluble polymers that contain ionisable functional groups that form a repeating pattern of polymers, creating a polymer chain . The drug is attached to the resin and is released when an appropriate interaction of ions and ion exchange groups occur . The area and length of the drug release and number of cross-link polymers dictate the rate at which the drug is released, determining the SR effect . </P>

Difference between slow release and controlled release tablets