Siratiazem [LRA 113] is a calcium channel antagonist that is structurally similar to diltiazem but has a branched alkyl group on the basic nitrogen. Siratiazem has been developed in an attempt to limit the in vivo N-demethylation that is known to occur with diltiazem. Preliminary binding and functional studies in cardiac and vascular tissues indicate that it not only binds to diltiazem binding sites but also exhibits Ca2+ channel blocking properties comparable to diltiazem. Siratiazem has a similar profile of activity to its parent compound, diltiazem, in that it blocks calcium channels in vascular, intestinal smooth muscle and cardiac tissue, and is least potent in cardiac muscle. At higher concentrations, siratiazem may also block cardiac sodium channels.