This property of senna was first described in the ninth century A.D. by Arabian physicians in the service of the caliph of Baghdad.
Senna’s reputation as a powerful laxative has grown through the ages. Senna can be found as an ingredient in many over-the-counter laxative products in the United States. Senna is also considered an important herb in traditional Chinese medicine, Indian Ayurvedic, and unani medicine.
The two species used most often for medicinal purposes are Alexandrian senna and Tinnevelly senna. The Alexandrian variety is obtained mainly from Egypt and the Sudan. Tinnevelly senna is primarily cultivated in India.
Senna contains naturally occurring chemicals called anthraquinone glycosides. They are strong laxatives that soften stools and increase the contractions of intestinal muscle, thereby stimulating bowel movements.
They also work by stimulating contractions of the colon muscles, which help to accelerate the passage of stool. Senna is considered among the strongest of the anthraquinone laxatives. Its effectiveness as a purgative has been supported by centuries of anecdotal reports as well as modern human and animal studies.
Senna is also approved in the United States and in European countries as an ingredient in over-the-counter and prescription laxative preparations. The herb is approved by the German government for any condition in which alleviating constipation or softening stools is desirable.
Senna may be recommended for people with hemorrhoids, anal fissures, or those undergoing surgery involving the abdomen, anus, or rectum. Senna may also be used to clear the bowel in order to improve the visibility of abdominal organs during an ultrasound procedure.
Clinical studies in the United States and abroad involving various age groups suggest that senna is effective in managing constipation associated with a number of causes including surgery, childbirth, and use of narcotic pain relievers.
A study in the medical journal Diseases of the Colon and Rectum showed that senna was able to prevent or treat postoperative constipation after proctologic surgery. The South African Medical Journal shows that treatment with senna was successful in 93%-96% of women suffering from postpartum constipation.
By comparison, only 51%-59% of women in the placebo group experienced relief. Senna is considered to be one of the more effective agents for relieving constipation caused by such narcotic pain relievers as morphine.
In another study published in the Journal of Pain and Symptom Management, researchers recommended the use of senna in terminal cancer patients with opiate-induced constipation, citing the effectiveness of the herb and its relatively low cost.
A study published in the medical journal Pharmacology suggests that a combination of senna and bulk laxatives can alleviate chronic constipation in geriatric patients.
People who choose to prepare senna using unprocessed leaves or pods may have difficulty determining exact dosages. No matter which form or preparation of senna is chosen, using the lowest effective dosage helps to avoid side effects.
Consumers who wish to brew a medicinal tea from unprocessed senna should use 1-2 tsp of the dried leaves of the herb per cup of boiling water and let it steep for about 10 minutes. Senna is generally considered to have an unpleasant taste, so adding sugar or honey to the mixture may help to make it more palatable.
Anise, ginger, chamomile, coriander, fennel, and peppermint can also be added to the tea to improve its taste and to reduce gas and cramping. Up to one cup of senna tea a day is recommended to alleviate constipation. It should not be taken for longer than one or two weeks.
Senna and other stimulant laxatives should not be used for longer than two to four weeks without medical supervision. Using senna longer than recommended can result in lazy bowel syndrome and permanent damage to the intestinal lining. Chronic use or misuse can also cause electrolyte and fluid imbalances, which can have adverse effects on the heart.
To prevent or treat constipation, most doctors recommend making dietary changes or trying milder bulk-forming laxatives such as psyllium before using senna or other anthraquinone purgatives. Dietary approaches involve eating a high-fiber diet, drinking six to eight glasses of water a day, and getting plenty of regular exercise.
Unless otherwise indicated by a doctor, senna should not be used by anyone with an intestinal obstruction, stomach inflammation, or intestinal inflammatory diseases such as Crohn’s disease, colitis, irritable bowel syndrome, or appendicitis. Senna should also be avoided by those with undiagnosed abdominal pain. Senna should not be used by children younger than age 12.
Senna should not be used by pregnant or breast-feeding women. It may significantly reduce drug absorption and lessen the efficiency of any over-the-counter or prescription medication. Children and seniors, who may be more susceptible to senna’s effects, should start with smaller dosages of the herb.
The side effects of senna include stomach cramps, diarrhea, and gas, which can be severe if the herb is used longer than recommended or in large amounts. The effects of senna can be immediate, sometimes too fast or intense.
These problems may be avoided by reducing the dosage and adding other herbs. More serious effects include fainting, dehydration, and such electrolyte disorders as low blood potassium, albuminuria, and hematuria. Potassium deficiency can lead to muscle weakness and disorders of heart function.
Potassium levels may drop even further if senna is combined with cardiac glycoside medications, diuretics, or corticosteroids. People using diet pills or teas should be sure that if senna is an ingredient they use the products short-term (a month or less).
Because of its potential effect on potassium levels, senna should not be combined with antiarrhythmic drugs, thiazide diuretics, corticoadrenal steroids, or licorice root without the supervision of a doctor.