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Ayurveda · Western herbalism

SennaSenna alexandrina (Cassia senna, Cassia angustifolia)

A stimulant laxative. In one 28-day trial, 1.0 g of senna gave a 69.2 percent response versus 11.7 percent on placebo; EMA limits use to 1 week.

Botanical name
Senna alexandrina (Cassia senna, Cassia angustifolia)
Part used
leaf and pod (fruit)
Also called
Alexandrian senna, Tinnevelly senna, Sennosides (the active glycosides)
Used in
Ayurveda, Western herbalism
Taken for
Constipation
Sold as
tablets, tea, loose leaf, capsules, syrup

The plant

Senna is the dried leaf or pod of Senna alexandrina (also written Cassia senna and Cassia angustifolia), a plant of the legume family. The leaf and pod are both used. The active compounds are sennosides, anthraquinone glycosides that the gut bacteria convert to the laxative metabolite rhein anthrone.

Senna reaches the shopper in three different kinds of product, and the difference matters. In the United States, senna laxatives sold with a Drug Facts label (sennosides tablets, syrups and combinations) are over-the-counter medicines, and FDA lists the OTC laxative monograph as pending a final rule. Senna teas and loose leaf are sold as herbal products or dietary supplements. In Europe, the European Medicines Agency (EMA) has published a monograph for senna leaf and pod preparations.

This page describes the botanical and what the sources report. Products with a Drug Facts panel are medicines governed by their labels, and it is not a statement about how to use them. Senna is also an ingredient in many multi-herb tea and “cleanse” blends, where its dose is usually not stated.

How the traditions use it

Ayurveda (about Ayurveda)

EMA’s assessment report records that in India senna leaves are used for loss of appetite, abdominal pain and liver disease, citing Indian materia medica texts of the 1970s, and that Nadkarni described the leaves and pods as purgatives. The same report places senna’s medicinal use in the Mediterranean world: it was introduced into European medicine by the Arabs in the 9th or 10th century. These are descriptions of use in the traditions, not findings about the body.

Western herbalism

In European practice senna has been used as a purgative for centuries, and the Pharmacopoeia Austriaca listed senna leaves as a laxative infusion in 1812. EMA now accepts it as a medicinal product for short-term use in occasional constipation, a conclusion that rests on its long record of use. Reference texts of the early twentieth century that EMA cites describe the leaf for habitual constipation but also note its tendency to nauseate.

What is in it

Senna contains sennosides A and B and related hydroxyanthracene derivatives. They pass through the small intestine unabsorbed and are converted by colon bacteria to rhein anthrone, which acts locally. In rats, rhein anthrone increased the water content of the large intestine, reduced net sodium and chloride absorption and stimulated prostaglandin release, and its laxative effect needed time for transit to the colon. These mechanisms come from animal and isolated-tissue studies in EMA’s report.

What the human trials show

Senna has the strongest evidence of any herbal laxative. A systematic review of over-the-counter therapies for chronic constipation (41 randomized trials of at least 4 weeks) gave senna and polyethylene glycol the top evidence grade (grade A, good evidence), ahead of psyllium and the magnesium salts.

The strongest single trial is a 28-day, double-blind, placebo-controlled study in 90 adults with chronic idiopathic constipation (mean age 42, 93 percent women). Patients received senna 1.0 g, magnesium oxide 1.5 g or placebo. The overall improvement rate was 11.7 percent on placebo, 69.2 percent on senna and 68.3 percent on magnesium oxide (P < 0.0001); spontaneous bowel movements and quality of life improved on both active treatments, and no severe treatment-related adverse events occurred.

The long-term question concerns the colon. A prospective case-control study of 202 patients with colorectal carcinoma, 114 with adenomas and 238 controls found no association between anthranoid laxative use and adenomas (odds ratio 1.0) or carcinoma (odds ratio 1.0), including with long-term use or melanosis coli. A study using aberrant crypt foci reached the same conclusion. A 2024 review of 43 publications found no convincing evidence that stimulant laxatives cause colon cancer, and structural changes seen at very high doses were reversible. Against that, a 1993 endoscopy series of 1,095 patients found pseudomelanosis coli, the brown colon discoloration of long-term anthranoid use, in 6.9 percent of people with normal findings, 9.8 percent with adenomas and 18.6 percent with carcinoma (relative risk 3.04), which is why the question persists.

In children, a review and a 640-patient chart series found blistering of the perineal skin in 2.2 percent of children on long-term senna, tied to high doses and prolonged stool contact. The authors write that avoiding senna for fear of tolerance or side effects has little scientific justification. We could find no trial of senna beyond 28 days that compared long-term safety directly.

StudyDoseWhat it found
Double-blind placebo-controlled trial, 90 adults with chronic idiopathic constipation PMID 32969946Senna 1.0 g vs magnesium oxide 1.5 g vs placebo, 28 daysOverall improvement 69.2% senna, 68.3% MgO, 11.7% placebo (P < 0.0001); no severe adverse events
Systematic review of 41 randomized OTC trials for chronic constipation PMID 33767108Various, at least 4 weeksSenna and polyethylene glycol rated grade A (good evidence); no serious adverse events reported
Prospective case-control study, 202 colorectal carcinoma, 114 adenoma, 238 controls PMID 10764708Anthranoid laxative use history, including long-termNo risk for adenomas (OR 1.0) or carcinomas (OR 1.0); melanosis coli not a risk factor
Critical review of 43 publications on stimulant laxative safety PMID 38887508Bisacodyl, sodium picosulfate, sennaNo convincing evidence of colon cancer; high-dose structural changes reversible
Literature review and chart review of 640 children given senna long term PMID 29429768Long-term sennaPerineal blistering in 17 (2.2%), linked to higher doses; tolerance concern called unjustified
Prospective endoscopy study, 1,095 patients (pseudomelanosis coli as a marker of chronic laxative use) PMID 8174962Chronic anthranoid laxative use (over 9 to 12 months)Pseudomelanosis 6.9% (normal), 9.8% (adenoma), 18.6% (carcinoma); relative risk 3.04

How much the studies and the texts used

EMA’s assessment report revised the daily dose range for senna leaf and pod preparations to 10 to 30 mg of hydroxyanthracene derivatives calculated as sennoside B, taken once daily at night, for adults and adolescents over 12. The monograph limits use to a maximum of one week, and notes that taking it two to three times in that week is usually sufficient. The trial above used 1.0 g of senna for 28 days. Over-the-counter labels state their own dose per tablet and a use limit on the Drug Facts panel. Tea doses are not standardized, and a cup of senna tea may carry an unpredictable amount of sennosides.

Doses here describe what studies and pharmacopoeias used. They are not a recommendation for any person; a clinician or pharmacist who knows your medicines and conditions is the right person to ask.

Side effects and cautions

Common effects are abdominal cramping, diarrhea and nausea. Chronic use or abuse can cause hypokalemia (low potassium), and EMA lists intestinal obstruction, Crohn’s disease, ulcerative colitis, appendicitis, abdominal pain of unknown origin and severe dehydration as reasons not to use it. Use in pregnancy and breastfeeding is contraindicated in the monograph because potential genotoxicity of anthraquinones has not been fully excluded; rhein was excreted into breast milk at 0.007 percent of the sennoside dose in a study of 20 women, and breastfed infants had normal stools.

Hypersensitivity and anaphylaxis have been reported. Case reports exist of liver injury with chronic overdose. EMA restricts duration to one week in view of the unresolved genotoxicity concern, and its monograph for cascara, another anthranoid laxative, states that long-term stimulant laxative use may lead to impaired bowel function and dependence on laxatives. Melanosis coli, a reversible brown colon pigmentation, is a recognized effect of long-term use.

Interactions

Chronic use lowers potassium, and EMA warns that low potassium can increase the activity of cardiac glycosides such as digoxin and interfere with antiarrhythmic medicines, including those that prolong the QT interval. Medicines that also lower potassium, such as diuretics, corticosteroids and licorice root, may aggravate the electrolyte loss. Senna also shortens transit time, which can change the absorption of other oral medicines taken at the same time, though the sources we read did not quantify this.

Senna on the shelf: the products that contain it

The products here name senna among their actives. How much of it a serving holds, and whether that matches any trial, is on each page.

Inno Supps Inno Cleanse 4.1 out of 5 from 12,407 ratings from Amazon · $1.33 a day Clean Nutra GI Defend 4.4 out of 5 from 1,152 ratings from Amazon · $1.00 a day

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Often paired or compared

Western Cascara sagrada Rhamnus purshiana (Frangula purshiana) TCM / Western Aloe vera Aloe vera (L.) Burm.f. (Aloe barbadensis Miller) Ayurvedic / Western Psyllium Plantago ovata TCM / Western Rhubarb root Rheum palmatum; Rheum officinale Western Flaxseed Linum usitatissimum

Common questions

Is senna a drug or a supplement?

Both exist. In the United States, senna laxatives with a Drug Facts panel are over-the-counter medicines. Senna teas and some capsules are sold as herbal products or supplements. In Europe EMA has a monograph for medicinal products of the leaf and pod.

What does the clinical evidence show?

A systematic review of OTC treatments for chronic constipation gave senna the top evidence grade alongside polyethylene glycol. In a 28-day trial of 90 adults, 69.2 percent improved on senna versus 11.7 percent on placebo.

Does senna cause colon cancer or damage the colon?

A prospective study of 554 people found no link between anthranoid laxative use and colorectal adenoma or carcinoma. A 2024 review found no convincing evidence of cancer and said structural changes at high doses were reversible. Melanosis coli, a brown discoloration, is a recognized effect of long use.

Why does the monograph limit it to one week?

EMA's assessment report restricts use to a maximum of one week because the genotoxic and carcinogenic potential of anthraquinones has not been conclusively excluded. Its cascara monograph adds that long-term stimulant laxative use may lead to impaired bowel function and dependence. Diet change and bulk-forming fiber are listed as first steps.

Can senna lower potassium?

Chronic use or abuse can cause low potassium. EMA warns this can raise the activity of cardiac glycosides and interfere with some heart-rhythm medicines.

Sources