antidiarrheal agents to find analogues suitable for the treatment of diarrhea predominant ibs the design concept was predicated on partitioning those structural components of the analogues responsible for the anti ibs properties from those which are toxic the alterations of the polyamine analogues fell into three categories a changing the distance between the nitrogens and the overall length of the molecule b keeping the overall length of the molecule the same but manipulating the ordering of the distance between the nitrogens and c altering the terminal groups within a series of compounds possessing the same backbone expansion of the methylene backbones from 3 3 3 systems e g denspm that were completely ineffective upon sc administration to stressed rats to 3 4 3 e g despm to 4 4 4 moieties dehspm resulted in improved anti ibs activity however further expansion of the backbone to a 5 4 5 base did not result in any corresponding improvement of efficacy the ordering and arrangement of the nitrogens within the methylene backbone seem to be critical to the compound 39 s effectiveness rearrangement of a 4 4 4 system to a 3 3 6 backbone of equal length actually reduced the activity in the rodent iibs model the effects of manipulating the terminal alkyl groups on a particular backbone on the molecule 39 s efficacy can be examined for several systems 3 3 3 denspm vs dipspm 3 3 6 de 3 3 6 vs dip 3 3 6 and 3 4 3 which was the most thoroughly studied backbone in the present work changing the terminal.