hi! Im IBS-A, and i used to take bentyl and Levsin, both did absolutely NOTHING for me! Now, I take Miralax....but only half the dose thats usually prescribed. If i take a full cap full of muralax, at regular prescription, I get D..however, if I take half a cap full, I get normal bms..however, i only take miralax when Im really really constipated..right now, the IBS diet seems to be normalizing my bms..:)