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Senna (Senna alexandrina) has a place in medical history going back to the ninth century when Arabian physicians introduced Europeans to this powerful laxative. The plant is native to the Nile in Sudan and Egypt and had been used for centuries before Europeans learned about it.

The Arabic word “sena” and the Greek “cassia” both refer to the bark of the plant, which peels back readily. It is, however, the leaves that are used medicinally.

Senna is one of the few herbal medicines approved by the Food and Drug Administration for over-the-counter use; it is probably the most widely used herbal medicine in the United States.

Rather than attempt to make an aqueous extract (tea) of the leaves, it may be easier and more reliable to use a proprietary product of known strength, such as Senexon, Senokot, or Senolax.

Active Ingredients

Senna leaves contain many anthraquinone compounds, including dianthrone glycosides, which make up 1.5 to 3 percent of the herb.

Sennosides A and B, which are rhein dianthrones, and sennosides C and D, which are aloe-emodin derivatives, are also present. Flavonoids, naphthalene glycosides, and beta-sitosterol have been identified.


Senna is used as a strong laxative. The anthraquinones stimulate the bowel, leading to evacuation after approximately ten hours.

This herb also provokes secretion of fluid and minerals into the large intestine and inhibits their reabsorption. It is suggested for situations in which a soft, easily passed stool is desirable, such as following rectal surgery or in addition to electrolyte solution for people preparing for colonoscopy or barium enema.

When the FDA determined that the hazards of phenolphthalein (formerly used in proprietary laxatives) were unacceptable, several companies replaced the phenolphthalein in their products, such as Ex-Lax and Perdiem Overnight Relief, with senna.

In our opinion, anthraquinone laxatives such as senna are not appropriate for regular use because they can cause problems such as dependence if used too often.


The usual dose is approximately 20 to 30 mg of anthraquinone derivatives calculated as
sennoside B.

If OTC drugs containing senna are used, dosing instructions on the label should be followed.
Senna-containing laxatives should not be used for more than eight or ten days except under medical supervision.

Special Precautions

Pregnant women should not use senna unless directed to do so by a physician.

Senna is not appropriate for children under the age of six.

People with intestinal blockage, undiagnosed stomach pain, or symptoms that might indicate appendicitis must avoid laxatives such as senna.

People with diarrhea and those with inflammatory bowel disease or intestinal ulcers must not use senna.

Adverse Effects

Senna can cause cramping (ranging from mild to severe), nausea, and diarrhea.

The urine may take on a reddish hue, which is harmless.

Serious complications generally occur only with prolonged use, which is not recommended.

Chronic use can lead to a dark discoloration of the lining of the colon and to laxative-induced diarrhea and weakening of the bones (osteomalacia). It may also lead to dependency, undermining the bowel’s ability to evacuate without stimulation. This sets up a vicious cycle.

Long-term use of a senna laxative can result in clubbing of the fingers or toes, as well as in loss of appetite and altered nutritional status.

With chronic use, too much potassium and other vital minerals may be lost, which can be very dangerous for those with heart rhythm irregularities.

Asthma and allergy are reported as a consequence of occupational exposure.

**Possible Interactions**

When potassium levels are reduced, there is a serious danger of interaction with heart drugs such as Lanoxin.

Other potassium-depleting medicines, such as diuretics (hydrochlorothiazide, Lasix, Hygroton, Lozol, Bumex, etc.) and the herbal medicine licorice may interact with senna to increase potassium loss, with consequently greater risk of heart rhythm disturbance.

Because senna reduces gastrointestinal transit time, pills taken the same day may not be absorbed completely.
If the dose of senna is such that the person becomes dehydrated, certain pain relievers such as acetaminophen may become more harmful to the kidneys.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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