Monohydrates of aminobenzenesulfonic acid derivatives and method for preparing thereof

摘要

A monohydrate of an aminobenzenesulfonic acid derivative represented by the following formula (I), for example, 2-(1-piperazinyl)-5-methylbenzenesulfonic acid, is substantially free from weight change due to moisture absorption and can be weighed accurately in manufacturing a pharmaceutical composition for the treatment of heart diseases comprising said monohydrate.