Novel sustained release tablet formulations

Claim 1

A sustained release pharmaceutical tablet containing as the active ingredient acetylsalicylic acid, said tablet being hydrodynamically balanced so that, upon contact with gastric fluid, said tablet acquires and maintains a bulk density of less than one thereby being buoyant in said fluid and remaining buoyant in the gastric fluid of the stomach until substantially all of the acetylsalicylic acid contained therein has been released therefrom, said tablet comprising a homogeneous mixture of acetylsalicylic acid, from about 0% to about 80% by weight of therapeutically inert, pharmaceutically acceptable adjunct materials, and from about 20% by weight to about 75% by weight of one or a mixture of hydrocolloids selected from the group consisting of methyl cellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose and sodium carboxymethylcellulose to provide, upon contact with gastric fluid, a water impermeable barrier on the surface of said tablet, said tablet being compressed to a hardness of from about 5 to about 6 S.C.U.