Controlled release formulations of orally-active medicaments

Claim 1

A compressed, controlled-release tablet suitable for oral administration, said tablet consisting essentially of an effective amount of an orally-active therapeutic agent selected from aspirin and a nonsteroidal arylalkanoic anti-inflammatory agent, a release-controlling agent, and an erosion-promoting agent, in proportions which provide a criticality factor between 20 and 450, calculated according to the formula: CA/(1/CS)=CF wherein: CA is the milligram per tablet content of therapeutic agent divided by the milligram per tablet content of release-controlling agent, CS is the milligram per tablet content of erosion-promoting agent divided by the milligram per tablet content of release-controlling agent, and CF is the criticality factor, said proportions including 0.8 to 1.6 weight percent per tablet of said release-controlling agent and 1.0 to 7.5 weight percent per tablet of said erosion-promoting agent, wherein the release-controlling agent is selected from the group consisting of cellulose acetate phthalate, cellulose acetate derivatives, shellac, zein, acrylic resins, ethylcellulose, hydroxypropylmethylcellulose phthalate, sandarac, and modified shellac; and wherein the erosion-promoting agent is selected from the group consisting of corn starch, rice starch, potato starch and other vegetable starches, modified starch, starch derivatives, cellulose, cellulose derivatives, modified cellulose, modified cellulose derivatives, alginic acid, alginates, bentonite, veagum, cross-linked polyvinyl pyrrolidone, ion exchange resins, and gums.