mixture comprising a dispersed gelling agent, for example polyvinylpyrrolidone, as taught in the '858 and '483 patents, or a mixture of microcrystalline cellulose and at least one alkali metal carboxyalkylcellulose, optionally with polyvinylpyrrolidone, as taught in the '146 and '762, and '832 patents, wherein the finished composition contains also one or more members of the group selected from a