Senokot tablets, max strength tablets and syrup all contain the active ingredient senna, which is a type of medicine called a stimulant laxative. It is used to treat constipation.
Senna works by stimulating the nerve endings in the walls of the large intestine (colon) and rectum. This causes the muscles in the intestinal wall to contract more often and with increased force. When these muscles contract (a process known as peristalsis), this moves the contents of the intestine through the colon to the rectum so that the bowel can be emptied. This relieves constipation.
Senna contains sennosides which are activated by the natural bacteria that are found in the colon, so it does not start working until it reaches this part of the gut. As senna increases the activity of the muscle in the gut it can cause stomach cramps.
Senokot tablets and syrup start to work eight to twelve hours after you take them. The recommended dose should be taken at night to produce relief from constipation the following morning.