SENNA IS AN ANTHRAQUINONE STIMULANT LAXATIVE, USED TO TREAT CONSTIPATION AND FOR BOWEL EVACUATION BEFORE INVESTIGATIONAL AND SURGERY. . THE ACTIVE ANTHRAQUINONES ARE LIBERATED INTO THE COLON FROM THE SENNOSIDE GLYCOSIDES BY COLONIC BACTERIA AND AN EFFECT USUALLY OCCURS WITHIN 6-8 HOURS OF ADMINISTRATION.