Sennosides are stimulant laxatives used to treat constipation, according to WebMD. Physicians also prescribe sennosides to patients who need to clean out their intestinal tracts before a test or surgical procedure.
Sennosides make the intestinal tract move and empty by keeping water in the intestines, explains WebMD, but it can take up to 12 hours for a patient to have a bowel movement after taking this medication. Sennosides are available as pills, liquid and dissolving strips, and they should be taken as directed on the package or per a physician's instructions. In most cases, this medication should not be used for more than seven days. Common brand names include Senokot and Senna.