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Senna

Senna alexandrina (Cassia angustifolia)
Evidence Level
Strong
2 Clinical Trials
4 Documented Benefits
4/5 Evidence Score

Senna is a stimulant laxative derived from the dried leaves and pods of Senna alexandrina (Cassia angustifolia). Its laxative effect comes from anthraquinone glycosides called sennosides, principally sennosides A and B, which are hydrolyzed by colonic bacteria into active rhein anthrones that stimulate peristalsis and alter water and electrolyte transport in the large intestine. Senna is well-established for short-term relief of occasional constipation and is included in palliative-care and opioid-induced constipation guidelines. It is important to use senna only as needed and for the shortest necessary time, as chronic daily use carries documented risks including cathartic colon, melanosis coli and electrolyte disturbances, and it is not a daily fiber supplement.

Studied Dose 15-30 mg sennosides/day for short-term use only (typically up to 1-2 weeks).
Active Compound Anthraquinone glycosides, principally sennosides A and B, hydrolyzed by colonic bacteria into active rhein anthrones.

Benefits

Short-Term Constipation Relief

Senna is a well-established stimulant laxative for short-term relief of occasional constipation. A typical bedtime dose produces a soft, formed bowel movement within 6-12 hours, helping reset normal transit when occasional irregularity occurs.

Supported by Trial 2

Pre-Procedure Bowel Preparation

Senna-based preparations are used in some bowel-cleansing protocols before colonoscopy and other procedures, where reliable, complete evacuation of stool is essential. Such use should always follow specific medical instructions.

Supported by Trial 1, Trial 2

Opioid-Induced Constipation Support

Senna is recommended as a first-line stimulant laxative for opioid-induced constipation in palliative care settings, where opioid analgesics predictably slow intestinal transit. Use is typically combined with stool softeners under clinical supervision.

Supported by Trial 1, Trial 2

Predictable Onset of Action

Senna's reliable 6-12 hour onset, taken at bedtime, makes it convenient for occasional use when a predictable next-morning result is needed. It is not appropriate as a daily maintenance product for chronic constipation.

Supported by Trial 2, Trial 1

Mechanism of action

1

Sennoside Activation in the Colon

Senna's sennoside glycosides pass intact through the small intestine and are hydrolyzed by colonic bacterial enzymes to active rhein anthrones in the large intestine. This localizes the laxative effect to the colon and explains the characteristic 6-12 hour onset.

2

Stimulation of Colonic Peristalsis

Rhein anthrones act on the myenteric plexus and on colonic smooth muscle, increasing the frequency and amplitude of propulsive contractions. The result is faster transit of fecal material through the colon.

3

Alteration of Water and Electrolyte Transport

Senna metabolites inhibit colonic Na+/K+-ATPase and modulate aquaporin-mediated water transport, reducing fluid absorption and slightly increasing colonic secretion. This softens stool and supports the propulsive effect.

Clinical trials

1
Cochrane Review of Laxatives in Palliative Care

Cochrane systematic review of randomized controlled trials evaluating laxatives, including senna, lactulose and combinations, for the management of constipation in palliative care patients.

5 included RCTs involving palliative-care patients with constipation, including many on opioid analgesics.

Senna and other commonly used laxatives showed broadly similar effectiveness for constipation in palliative care, with evidence limited by small sample sizes and heterogeneous outcomes. The review highlights senna as a reasonable first-line option in this population while calling for higher-quality trials.

2
Sodium Picosulfate vs Placebo for Chronic Constipation

Multicenter, 4-week, double-blind, randomized, placebo-controlled trial of a stimulant laxative (sodium picosulfate, mechanistically similar to senna) in 367 adults with chronic constipation. Primary outcome was complete spontaneous bowel movements per week.

367 adults with chronic constipation defined by Rome III criteria.

The active stimulant laxative increased complete spontaneous bowel movements from 0.9 to 3.4 per week versus 1.1 to 1.7 for placebo, and improved quality-of-life measures. Treatment was generally well tolerated; the trial supports the short-term efficacy of stimulant laxatives in this class.

Side effects and drug interactions

Common Potential side effects

Abdominal cramping, gas and bloating, especially at higher doses.
Diarrhea and urgency if dose is excessive or repeated.
Chronic daily use can cause cathartic colon with reduced colonic motility.
Long-term use is associated with melanosis coli, a benign brown pigmentation of the colonic mucosa.
Prolonged use can cause electrolyte imbalance, particularly hypokalemia.

Important Drug interactions

Prolonged use can cause hypokalemia, potentiating digoxin toxicity.
Hypokalemia can interact with antiarrhythmic drugs and increase arrhythmia risk.
May reduce absorption of oral medications by accelerating intestinal transit.
Combining with diuretics worsens potassium loss and electrolyte disturbances.

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Frequently asked questions about Senna

What is senna used for?

Senna is an herbal stimulant laxative used for short-term relief of occasional constipation. Its compounds (sennosides) stimulate the bowel to contract, producing a bowel movement, usually within 6 to 12 hours.

How does senna work, and when?

Senna stimulates the intestinal muscles to move stool along, typically working within 6 to 12 hours, so it is often taken at bedtime for a morning result. It is for short-term, occasional use, not daily long-term use.

How much senna should I take?

Follow product labeling for the standardized sennoside content, using the lowest effective amount. Take it with plenty of water, and do not exceed the recommended duration (usually about a week).

Is senna safe?

For occasional short-term use it is generally safe. However, regular long-term use of stimulant laxatives can lead to dependence and electrolyte problems, so it should not be used daily for extended periods. Pregnant women and those with bowel conditions should check with a doctor.

What is Senna?

Senna is a stimulant laxative derived from the dried leaves and pods of Senna alexandrina (Cassia angustifolia). Its laxative effect comes from anthraquinone glycosides called sennosides, principally sennosides A and B, which are hydrolyzed by colonic bacteria into active rhein anthrones that stimulate peristalsis and…

What is the recommended dosage of Senna?

The clinically studied dose is 15-30 mg sennosides/day for short-term use only (typically up to 1-2 weeks). Always follow the product label and check with a healthcare provider for personal advice.

Is Senna safe, and does it have side effects?

For most healthy adults, Senna is well tolerated at studied doses. Reported effects can include: Abdominal cramping, gas and bloating, especially at higher doses. Diarrhea and urgency if dose is excessive or repeated. It may also interact with some medications. Senna is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Senna interact with any medications?

Possible interactions include: Prolonged use can cause hypokalemia, potentiating digoxin toxicity. Hypokalemia can interact with antiarrhythmic drugs and increase arrhythmia risk. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Senna?

NutraSmarts rates the evidence for Senna as Strong (4 out of 5). It is backed by 2 clinical trials and 2 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(2 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Candy B, Jones L, Larkin PJ, Vickerstaff V, Tookman A, Stone P. Laxatives for the management of constipation in people receiving palliative care. Cochrane Database Syst Rev. 2015;(5):CD003448. doi: 10.1002/14651858.CD003448.pub4.PubMedUsed to support: Cochrane systematic review of laxatives (including senna) for constipation in palliative care, finding broadly similar effectiveness across agents in a limited evidence base.
  2. Mueller-Lissner S, Kamm MA, Wald A, Hinkel U, Koehler U, Richter E, Bubeck J. Multicenter, 4-week, double-blind, randomized, placebo-controlled trial of sodium picosulfate in patients with chronic constipation. Am J Gastroenterol. 2010;105(4):897-903. doi: 10.1038/ajg.2010.41.PubMedUsed to support: Randomized placebo-controlled trial of a stimulant laxative class showing significant increases in complete spontaneous bowel movements in chronic constipation; supports general efficacy of stimulant laxatives.