Be careful not to abuse products with senna and cascara sagrada because they can cause lazy bowel syndrome. Also, some gastroenterologists think this is the reason for black colon – which has been seen in some patients having colonoscopies.
I recommend trying Renew Life’s Organic Bowel Cleanse (30 day supply). It contains natural fiber, proprietary blend of flaxseed, oat bran and acacia fiber yielding 1350 mg., 450 mg. of rhubarb root, 100 mg. blend of ginger root, fennel seed and other important ingredients that help heal the digestive tract while increasing elimination .
Also, I recommend Slippery Elm Tea or capsules which soothes inflammation and cleanses excess waste from the colon. You can also try slippery elm tea as an enema.