Tocainide Monohydrochloride S Isomer, also known as TMSI, is a pharmaceutical compound used to treat various heart rhythm disorders. However, it is always beneficial to have alternatives or synonyms for specific medications. In this case, some substitute terms for Tocainide Monohydrochloride S Isomer can include Tocainide HCl S-isomer, Tocainide MHC, or simply S-Tocainide. These terms essentially refer to the same medication, but with different nomenclature. It is important to note that these synonyms should only be used when referring to the same active ingredient and under professional medical guidance.