Membrane-coated tablets: a system for the controlled release of drugs

Membrane-coated tablets were developed to provide a dosage form which exhibits zero-order kinetics. The delivery system consisted of a soluble tablet core surrounded by a porous membrane which controls the diffusion rate. In the system studied, the diffusion rate of potassium chloride was found to be more constant than with other controlled-release products and independent of pH changes within the physiological range. The release profile of a drug can be varied by changing the composition of the membrane. Substantial amounts of the active substance can be loaded into membrane-coated tablets. The membrane protects the gastric mucosa from direct contact with the undissolved active substance. This delivery system has a potential for use with all water-soluble agents where a controlled release is desirable.