| abstract |
Drugs that are freely or highly soluble in water are formulated as unit dosage forms by incorporating them into polymeric matrices comprised of high molecular weight hydrophilic polymers that swell upon imbibition of water. The dosage form can be a single compressed tablets, or two or three compressed tablets retained in a single gelatin capsule. The oral formulation is designed for gastric retention and controlled delivery of an incorporated drug into the gastric cavity, and thus administered, the drug is released from the matrix into the gastric fluid by solution diffusion. The swollen polymeric matrix, having achieved sufficient size, remains in the gastric cavity for several hours if administered while the patient is in the fed mode, and remains intact long enough for substantially all of the drug to be released before substantial erosion of the matrix occurs. The swelling matrix lowers the accessibility of the gastric fluid to the drug and thereby limits the drug release rate. This process, together with diffusion retardation by selection of specific polymers, polymer molecular weights, and other variables, results in a sustained and controlled delivery rate of the drug to the gastric environment. |