Senna

Scientific Name(s): Cassia acutifolia Delile, syn. with Cassia senna L. Also includes references to C. angustifolia Vahl. Family: Fabaceae (beans)

Clinical Overview

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Uses of Senna

Senna is most commonly used as a laxative.

Senna Dosing

Senna leaves or pods have been used as a cathartic laxative at doses of 0.6 to 2 g/day, with a daily dose of sennoside B from 20 to 30 mg. Senna should not be used at higher doses or for extended periods of time.

Contraindications

Patients with intestinal obstruction.

Pregnancy/Lactation

Documented endometrial stimulation and mutagenic and genotoxic. Avoid use

Senna Interactions

None well documented.

Senna Adverse Reactions

The chronic use of senna has resulted in pigmentation of the colon, reversible finger clubbing, cachexia, and a dependency on the laxative.

Toxicology

Various case reports of senna toxicity are available, and include coma and neuropathy after ingestion of a senna-combination laxative as well as hepatitis after chronic use of the plant.

Botany

C. acutifolia is native to Egypt and the Sudan while C. angustifolia is native to Somalia and Arabia. Plants known as “wild sennas'' ( C. hebecarpa Fern. and C. marilandica L.) grow on moist banks and woods in the eastern US. This plant should not be confused with “cassia,'' a common name for cinnamon. Senna is a low branching shrub, growing to about 3 feet in height. It has a straight woody stem and yellow flowers. 1 The top parts are harvested, dried and graded. The hand-collected senna is known as Tinnevally senna. Leaves that have been harvested and graded mechanically are known as Alexandria senna. There are over 400 known species of cassia. 1

History

Senna was first used medicinally by Arabian physicians as far back as the 9th century A.D. 1 It has long found use in traditional Arabic and European medicine as well, primarily as a cathartic. The leaves have been brewed and the tea administered for its strong laxative effect. Because it is often difficult to control the concentration of the active ingredients in the tea, an unpredictable effect may be obtained. Therefore, standardized commercial dosage forms have been developed, and these concentrates are available as liquids, powders and tablets in over-the-counter laxatives. The plant derives its name from the Arabic “sena'' and from the Hebrew word “cassia,'' which means “peeled back,” a reference to its peelable bark.

Chemistry

Senna contains anthraquinones including dianthrone glycosides (1.5% to 3%), sennosides A and B (rhein dianthrones), sennosides C and D (rhein aloe-emodin heterodianthrones). Numerous minor sennosides have been identified, and all appear to contribute to the laxative effect. The plant also contains free anthroquinones in small amounts including rhein, aloe-emodin, chrysophanol and their glycosides. 2 , 3

Senna pods also contain the same rhein dianthrone glycosides as the leaves.

Carbohydrates in the plant include 2% polysaccharides, and approximately 10% mucilage consisting of galactose, arabinose, rhamnose and galacturonic acid. 2 , 3 Other carbohydrates include mannose, fructose, glucose, pinitol and sucrose. 2

Flavonols present include isorhamnetin and kaempferol. Glycosides 6-hydroxymusizin and tinnevellin are also found.

Other constituents in senna include chrysophanic acid, salicylic acid, saponin, resin, mannitol, sodium potassium tartrate and trace amounts of volatile oil. 2 , 4

Senna Uses and Pharmacology

Senna is a potent laxative. Its cathartic effects can be obtained from a tea prepared from one or two teaspoonfuls of dried leaves. Senna's use in treating constipation is well documented. It is one of the most popular laxatives, especially in the elderly. 5

Senna has also been studied for long-term laxative treatment. 6

Laxative actions because of prostaglandin-mediated action of sennosides. 7 Indomethacin can partly inhibit the actions of sennosides A and B. 2 However, conflicting reports suggest that prostaglandins do not contribute to the laxative effect. 8 , 9 In addition, studies on the rat colon suggest that the laxative effect produced by senna may involve histamine formation. 10

Metabolism of anthranoid laxatives has been reported, 11 , 12 as has the metabolism of sennosides. 13 , 14 , 15

Many reports are available discussing senna's role in constipation, 16 , 17 its use in the elderly, 18 , 19 , 20 , 21 , 22 in psychiatric patients, 23 in spinal cord injury patients 24 and in pregnancy, where it is the stimulant laxative of choice. 25 In cancer treatment protocols, senna has also been noted to reverse the constipating effects of narcotics, and may prevent constipation if given with the narcotic. 26 It may, however, cause more adverse effects than other laxatives, primarily abdominal pain. 27 Senna has also been studied in chronic constipation, 28 Castor oil was superior to senna for chronic constipation sufferers in another report. 29

Senna may affect influence on intestinal transit time. 30 , 31 , 32 Its effectiveness as part of a cleansing regimen to evacuate the bowels in preparation for such tests as colonoscopies or barium enemas is documented. 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 Results from these studies include reduced ingestion of commercial Golytely solution and simethicone when given with senna, 38 and more effective colon cleansing with senna in combination with polyethylene glycol electrolyte lavage solution, compared to the solution alone. 39

Several mechanisms are postulated as to how senna acts as an effective laxative. The anthraquinone glycosides are hydrolyzed by intestinal bacteria to yield the active, freed anthraquinones. Alternately, it has been suggested that anthraquinones are absorbed in small quantities from the small intestine and hydrolyzed in the liver. The resultant anthraquinones are secreted into the colon. 44 One report using human intestinal flora finds sennoside A to eventually be converted to rheinanthrone, which is the active principle causing peristalsis of the large intestines. Sennosides A and B also play a role in inducing fluid secretion in the colon. Sennosides irritate the lining of the large intestine, causing contraction, which results in a bowel movement approximately 10 hours after the dose is taken. 1

Prostaglandins may also be involved in the laxative actions. 2 The kinetics of senna constituents rhein and aloe-emodin have been investigated in man. 45

The senna constituents, aloe-emodin and beta-sitosterol, possess inhibitory activity against cancer cells in mice. 2 , 4

Senna was not found to have antidiabetic activity when tested in diabetic mice. 46

Dosage

Senna leaves or pods have been used as a cathartic laxative at doses of 0.6 to 2 g/day, with a daily dose of sennoside B from 20 to 30 mg. Senna should not be used at higher doses or for extended periods of time. 47

Pregnancy/Lactation

Documented endometrial stimulation and mutagenic and genotoxic. 48 , 49 Avoid use.

Interactions

None well documented.

Adverse Reactions

Generally, senna may cause mild abdominal discomfort such as cramping. Prolonged use may alter electrolytes. Patients with intestinal obstruction should avoid senna. 2

Chronic use of any laxative, in particular irritant laxatives such as senna, often results in a “laxative-dependency syndrome'' characterized by poor gastric motility in the absence of repeated laxative administration. Other reports of laxative abuse include laxative-induced diarrhea, 50 , 51 and osteomalacia and arthropathy associated with prolonged use of the product. 52

The chronic use of anthroquinone glycosides has been associated with pigmentation of the colon (melanosis coli). Several cases of reversible finger clubbing (enlargement of the ends of the fingers and toes) have been reported following long-term abuse of senna-containing laxatives. 53 , 54 , 55 One report described a woman who developed finger clubbing following ingestion of from 4 to 40 Senokot tablets per day for about 15 years. 56 Clubbing reversed after the laxative was discontinued. The mechanism has been postulated to be related to either increased vascularity of the nail beds or a systemic metabolic abnormality secondary to chronic laxative ingestion.

Senna abuse has been associated with the development of cachexia and reduced serum globulin levels after chronic ingestion. 57

Case reports include occupational asthma and rhinoconjunctivitis from a factory worker exposed to senna-containing hair dyes, 58 and asthma and allergy symptoms from workers in a bulk laxative manufacturing facility. 59

Toxicology

Risk assessment for senna's use during pregnancy has been addressed. 60 One review suggests senna to be the “stimulant laxative” of choice during pregnancy and lactation. 25 Uterine motility was not stimulated by sennosides in one report in pregnant ewes. 61 None of the breast-fed infants experienced abnormal stool consistency from their mothers' ingestion of senna laxatives. The constituent rhein, taken from milk samples varied in concentration from 0 to 27 mg/ml, with between 89% to 94% of values ≤ 10 mg/ml. 62 , 63 Nonstandardized laxatives are not recommended during pregnancy. 2

Myenteric neurons in the rat colon are not destroyed by sennosides, as had been earlier suggested. 64 , 65 , 66 Anthraquinone purgatives in excess were said to have caused degeneration of neurons. Toxicity studies separating toxic components of senna's anthraquinone derivatives have been performed. 67

Various case reports of senna toxicity are available, and include coma and neuropathy after ingestion of a senna-combination laxative, 68 and hepatitis after chronic use of the plant. 69

Bibliography

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