The senna shrub grows in India, Pakistan, and China. The leaves and pods are used medicinally.
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1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
20 to 60 mg of sennosides per day for no more than ten days
Senna is considered a stimulant laxative because it stimulates bowel muscle contractions. Senna is the most popular of these stimulant herbs.
Senna contains hydroxyanthracene glycosides known as sennosides. These glycosides stimulate colon activity and thus have a laxative effect. Also, these glycosides increase fluid secretion by the colon, with the effect of softening the stool and increasing its bulk.1 Double-blind trials have confirmed the benefit of senna in treating constipation.1 , 2Constipation induced by drugs such as the anti-diarrhea medicine loperamide (Imodium) has also been shown to be improved by senna in a clinical trial.3
The laxatives most frequently used world-wide come from plants. Herbal laxatives are either bulk-forming or stimulating.
Bulk-forming laxatives come from plants with a high fiber and mucilage content that expand when they come in contact with water; examples include psyllium, flaxseed, and fenugreek. As the volume in the bowel increases, a reflex muscular contraction occurs, stimulating a bowel movement. These mild laxatives are best suited for long-term use in people with constipation.
Many doctors recommend taking 7.5 grams of psyllium seeds or 5 grams of psyllium husks, mixed with water or juice, one to two times per day. Some doctors use a combination of senna (18%) and psyllium (82%) for the treatment of chronic constipation. This has been shown to work effectively for people in nursing homes with chronic constipation.4
Stimulant laxatives are high in anthraquinone glycosides, which stimulate bowel muscle contraction. The most frequently used stimulant laxatives are senna leaves, cascara bark, and aloe latex. While senna is the most popular, cascara has a somewhat milder action. Aloe is very potent and should be used with caution. Other stimulant laxatives include buckthorn, alder buckthorn (Rhamnus frangula), and rhubarb (Rheum officinale, R. palmatum).
People in northern Africa and southwestern Asia have used senna as a laxative for centuries. It was considered a “cleansing” herb because of its cathartic effect. In addition, the leaves were sometimes made into a paste and applied to various skin diseases. Ringworm and acne were both treated in this way.
Senna contains hydroxyanthracene glycosides known as sennosides. These glycosides stimulate colon activity and thus have a laxative effect. Also, these glycosides increase fluid secretion by the colon, with the effect of softening the stool and increasing its bulk.6 Double-blind trials have confirmed the benefit of senna in treating constipation.7 , 8 Constipation induced by drugs such as the anti-diarrhea medicine loperamide (Imodium®) has also been shown to be improved by senna in a clinical trial.9
A double-blind trial showed that senna was more effective as a preparatory agent for bowel surgery than the commonly used polyethylene glycol (PEG).10 Patients scheduled to undergo bowel surgery received either 120 mg of senna in a glass of water or 118 mg of PEG in about 2–3 quarts of water the night before surgery. Surgeons rated the efficacy of senna at clearing the bowels at 70%, compared to 58% efficacy for PEG. Supplementation with senna for this purpose should always be supervised by the surgeon.
People using over-the-counter senna products should carefully follow label instructions. An extract in capsules or tablets providing 20–60 mg of sennosides per day is sometimes recommended.11 This can be continued for a maximum of ten days. Use beyond ten days is strongly discouraged. If constipation is not alleviated within ten days, people should seek the help of a healthcare professional.
Certain medicines interact with this supplement.
Bisacodyl , a laxative similar in action to senna (Cassia senna, Cassia angustifolia), givenwith digoxin decreased serum digoxin levels in healthy volunteers compared with digoxin alone.12 In patients taking digoxin, laxative use was also associated with decreased digoxin levels.13 In addition, concern has been expressed that overuse or misuse of senna may deplete potassium levels and increase both digoxin activity and risk of toxicity.14 However, overuse of senna could also decrease digoxin activity because, as noted, laxatives can decrease the levels of the drug.
Some people may develop a dependency on senna for normal bowel movements. Therefore, senna must not be used for more than ten consecutive days. Chronic senna use can also cause loss of fluids, low potassium levels and diarrhea, all of which can lead to dehydration and potentially negative effects on the heart and muscles. The safety of senna during pregnancy and breast-feeding is controversial. Most guidelines suggest avoiding senna during the first trimester of pregnancy.15 , 16 It is best to consult a physician. Senna is not recommended for children under the age of ten years. People with Crohn’s disease, ulcerative colitis, appendicitis, intestinal obstructions, and abdominal pain should not supplement with senna.17
There is one case report of a woman who developed liver failure after ingesting a large amount of senna (1 liter of a tea containing 70 grams of dried herb) daily for more than three years.18 Senna was suspected, though not proven, to be the cause of the liver failure.
1. Passmore AP, Davies KW, Flanagan PG, et al. A comparison of Agiolax and Lactulose in elderly patients with chronic constipation. *Pharmacol* 1993;47(suppl 1):249–52.
2. Kinnunen O, Winblad I, Koistinen P, Salokannel J. Safety and efficacy of a bulk laxative containing senna versus lactulose in the treatment of chronic constipation in geriatric patients. *Pharmacol* 1993;47(suppl 1):253–5.
3. Ewe K, Ueberschaer B, Press AG. Influence of senna, fibre, and fibre+senna on colonic transit in loperamide-induced constipation. *Pharmacol* 1993;47(suppl 1):242–8.
4. Passmore AP, Wilson-Davies K, Flanagan PG, et al. Chronic constipation in long stay elderly patients: a comparison of lactulose and senna-fiber combination. BMJ 1993; 307:769–71.
5. Valverde A, Hay JM, Fingerhut A, et al. Senna vs polyethylene glycol for mechanical preparation the evening before elective colonic or rectal resection: a multicenter controlled trial. French Association for Surgical Research. Arch Surg 1999;134:514–9.
6. Leng-Peschlow E. Dual effect of orally administered sennosides on large intestinal transit and fluid absorption in the rat. J Pharm Pharmacol 1986;38:606–10.
7. Passmore AP, Davies KW, Flanagan PG, et al. A comparison of Agiolax and Lactulose in elderly patients with chronic constipation. Pharmacol 1993;47(suppl 1):249–52.
8. Kinnunen O, Winblad I, Koistinen P, Salokannel J. Safety and efficacy of a bulk laxative containing senna versus lactulose in the treatment of chronic constipation in geriatric patients. Pharmacol 1993;47(suppl 1):253–5.
9. Ewe K, Ueberschaer B, Press AG. Influence of senna, fibre, and fibre+senna on colonic transit in loperamide-induced constipation. Pharmacol 1993;47(suppl 1):242–8.
10. Valverde A, Hay JM, Fingerhut A, et al. Senna vs polyethylene glycol for mechanical preparation the evening before elective colonic or rectal resection: a multicenter controlled trial. French Association for Surgical Research. Arch Surg 1999;134:514–9.
11. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. Montvale, NJ: Medical Economics, 1998, 722–4.
12. Wang DJ, Chu KM, Chen JD, et al. Drug interaction between digoxin and bisacodyl. J Formos Med Assoc 1990;89:913, 915–9 [in Chinese].
13. Botzler R, Ritter U. Effect of laxative measures on the serum concentration of digoxin in the human. Leber Magen Darm Nov 1982; 14(6):255–7 [in German].
14. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Healthcare Professionals. London: Pharmaceutical Press, 1996, 244.
15. Mengs U. Reproductive toxicological investigations with sennosides. Arzneimittelforschung 1986;36:1355–8.
16. Faber P, Strenge-Hesse A. Relevance of rhein excretion into breast milk. Pharmacol 1988;36(suppl 1):212–20.
17. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 204–8.
18. Vanderperren B, Rizzo M, Angenot L, et al. Acute liver failure with renal impairment related to the abuse of senna anthraquinone glycosides. Ann Pharmacother 2005;39:1353–7.
Last Review: 05-01-2013
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