Sustained release tablet formulations

Claim 1

A two-layer tablet comprising: a first layer containing one or more antacid substances and therapeutically inert pharmaceutically acceptable adjunct materials free of sustained release ingredients; and a second layer containing as the active ingredient, one or more antacid compounds, said tablet being hydrodynamically balanced so that, upon contact with gastric fluid, said second layer 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 antacid compounds contained therein have been released therefrom, said second layer comprising a homogeneous mixture of said antacid compounds, 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 methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose and sodium carboxymethylcellulose to provide, upon contact with gastric fluid, a water impermeable barrier on the surface of said second layer, said tablet being compressed to a hardness of from about 12 to about 14 S.C.U.