Transdermal therapeutic systems can release drug substances slowly and in a controlled manner from a drug depot. To provide a slow-release form of ursolic and oleanolic acid amide-spacered dimers were synthesized from the parent acids and diamines of variable chain lengths. These dimers were assayed in sulforhodamine B (SRB) assays for their cytotoxicity since as a pre-requisite for their use in slow-release forms these substances must not exert any unfavorable side-effects such as cytotoxicity. As a result of long term incubation up to 96 hours, none of these compounds showed any significant cytotoxicity in sulforhodamine B assays.