No laxative, including senna, should be used for longer than 7 to 10 days. Chronic use of laxatives may lead to “lazy-bowel syndrome” -- a dependency on laxatives to have any bowel movements as the muscles of the stomach and intestines gradually lose the ability to contract without being stimulated by the laxative.
Major Side Effects
If senna is used in high doses or for prolonged periods of time, it can lead to reduced potassium levels in the body. Low potassium levels can result in muscle weakness and potentially dangerous changes in heart rhythm.
Chronic, long-term use of senna may also result in aching joints, weakened bones or muscles, and loss of weight due to decreased appetite. Cases of "clubbing" or rounding that occurs at the ends of the fingers have also been reported from taking senna for long periods of time.