Senna

Metadata

• Common Names: Senna, Alexandrian Senna, Tinnevelly Senna (English); Senna, Sennesblaetter (German)
• Botanical Name: Senna alexandrina Mill. (syn. Cassia senna L., Cassia angustifolia Vahl)
• Plant Family: Fabaceae (Leguminosae)
• Part Used: Leaf (Sennae folium); Fruit/Pod (Sennae fructus)
• Evidence Quality Rating: Strong (well-characterized pharmacology; well-established regulatory status; extensive clinical use)

Approved Indications

Commission E

• Constipation

ESCOP

• Short-term use in cases of occasional constipation
• Situations requiring easy defecation with soft stool (e.g., in patients with anal fissures, hemorrhoids, after rectal/anal surgery)
• Bowel evacuation before diagnostic or surgical procedures

EMA/HMPC

• Well-established use (leaf and fruit): Short-term use in cases of occasional constipation
• Well-established use: For pre-procedural bowel preparation (radiological examination, colonoscopy)
• The EMA grants “well-established use” status, reflecting the strong evidence base and extensive clinical history

Agreement/Disagreement Between Bodies

• All three bodies agree: senna is indicated for occasional constipation with strict short-term use limitations
• All emphasize that senna should not be used for more than 1 week without medical supervision
• ESCOP and EMA include pre-procedural bowel preparation
• No significant disagreements between bodies
• Universal emphasis on short-term use only

Conditions Treated

• Occasional constipation
• Bowel preparation for colonoscopy, radiological examination, or surgery
• Post-surgical constipation (short-term)
• Constipation in palliative care / opioid-induced constipation (off-label but common clinical practice)

Mechanism of Action

• Sennosides A and B (dianthrone glycosides, representing ~2.5% of active components): These are prodrugs that are not absorbed in the upper GI tract
• Colonic bacterial hydrolysis: Sennosides are hydrolyzed by colonic bacterial beta-glucosidases to release the active metabolite rhein anthrone
• Dual mechanism of rhein anthrone:
  1. Stimulation of colonic motility: Rhein anthrone stimulates Auerbach’s (myenteric) plexus, increasing propulsive peristaltic contractions and reducing segmental (non-propulsive) contractions
  2. Secretory/anti-absorptive effect: Inhibits electrolyte and water absorption from the colon; stimulates chloride secretion, resulting in net fluid accumulation in the colonic lumen
• Prostaglandin involvement: Rhein anthrone stimulates PGE2 release into the colonic lumen, which contributes to both motility stimulation and secretory effects
• Onset of action: 6-10 hours (typically taken at bedtime for morning effect)
• Site of action: Exclusively the colon (sennosides pass through the small intestine intact)

Clinical Evidence Summary

Constipation

• Senna is one of the most extensively used stimulant laxatives worldwide; clinical efficacy is well-established
• Multiple controlled clinical trials confirm efficacy for constipation
• Comparison studies: Senna has been compared to lactulose, polyethylene glycol (PEG), and other laxatives; generally comparable efficacy, often faster onset
• Systematic review (PMC, 2024): Critical analysis of stimulant laxative safety found that senna is effective and that short-term use is safe

Bowel Preparation

• Senna is used as a component of bowel preparation regimens for colonoscopy
• Studies show adequate bowel cleansing when combined with other agents

Opioid-Induced Constipation

• Commonly used in palliative care and oncology for opioid-induced constipation
• Clinical practice guidelines in palliative medicine often include senna as a first-line option

Long-Term Use Concerns

• There are no well-designed RCTs evaluating long-term senna use safety
• The evidence for or against chronic use damage is largely observational and controversial

European vs US/Anglophone Consensus

• Broad consensus: Senna is accepted in both European and US practice as an effective stimulant laxative
• FDA-approved as an OTC laxative in the US (Senokot, Ex-Lax, generic preparations)
• Well-established use per EMA in Europe
• Both traditions emphasize short-term use only
• Available in pharmacies worldwide
• The main area of debate is around long-term safety (melanosis coli, “cathartic colon”) — this debate exists in both traditions
• US and European guidelines are largely aligned: senna is effective, well-tolerated for short-term use, and should not be used chronically without medical supervision

Safety Profile

Contraindications

• Bowel obstruction or ileus
• Acute inflammatory bowel disease (Crohn’s disease, ulcerative colitis flares)
• Appendicitis or suspected appendicitis
• Severe dehydration / Electrolyte imbalance (pre-existing)
• Undiagnosed abdominal pain
• Children under 12 years (some authorities say under 6; varies by country)
• First trimester of pregnancy (traditionally avoided; see below)

Drug Interactions

• Cardiac glycosides (digoxin): Senna-induced hypokalemia may potentiate digoxin toxicity — clinically significant interaction
• Diuretics (thiazides, loop diuretics): Additive hypokalemia risk
• Corticosteroids: Additive hypokalemia risk
• Antiarrhythmics: Hypokalemia can affect cardiac conduction
• Other laxatives: Additive effect, increased risk of electrolyte imbalance
• Licorice root: Additive hypokalemia risk (relevant to STW 5/Iberogast)

Side Effects

• Abdominal cramping and pain (common, dose-dependent)
• Diarrhea (dose-dependent)
• Nausea
• Discoloration of urine (yellowish-brown or red, harmless)
• Chronic use complications:
  • Melanosis coli: Brown pigmentation of colonic mucosa; develops with chronic use (months to years); reversible upon discontinuation; NOT associated with increased colon cancer risk
  • Electrolyte imbalance: Hypokalemia, hypocalcemia, metabolic acidosis or alkalosis
  • Laxative dependence: Loss of normal colonic motor function with prolonged use
  • “Cathartic colon” (controversial): Historical concept of colonic damage from chronic stimulant laxative use; modern evidence suggests this may have been overstated [Source: PMC 2024 critical review]

Pregnancy/Lactation

• Pregnancy: Possibly safe for short-term use (up to 1 week) in the second and third trimesters; dose of 10-60 mg sennosides at bedtime for maximum 10 days
• First trimester: Traditionally avoided due to theoretical abortifacient concerns; no studies confirming teratogenicity
• Breastfeeding: Small amounts of sennoside metabolites may pass into breast milk; no adverse effects observed in breastfed infants in published studies; generally considered compatible with breastfeeding in short-term use

Clinical Dosage

Forms and Ranges

• Standardized to hydroxyanthracene derivatives (calculated as sennoside B):
  • Adults: 15-30 mg sennosides per day, taken once daily at bedtime
  • Start with lowest effective dose; increase only if needed
  • Maximum: 30 mg sennosides per day
• Senna leaf tea: 0.5-2 g dried leaf per cup, steeped 10 minutes, once daily at bedtime
• Senna tablets (standardized): Per manufacturer; typically 8.6-17.2 mg sennosides per tablet, 1-2 tablets at bedtime
• Duration: Maximum 1 week without medical supervision; if constipation persists, seek medical evaluation
• Bowel preparation: Higher doses per specific protocol (physician-directed)

Dose Titration Principle

• The correct dose is the lowest dose necessary to produce a comfortable, formed soft stool
• ESCOP and EMA both emphasize starting with the lowest recommended dose

Key Standardized Products

• Senokot (Reckitt Benckiser): Standardized senna tablets and syrup; US and international markets
• X-Prep / Picoprep (bowel preparation formulations containing senna)
• Sennae folium per European Pharmacopoeia: Minimum 2.5% hydroxyanthracene glycosides (calculated as sennoside B)
• Multiple generic standardized senna products available globally

Sources

• EMA/HMPC European Union Herbal Monograph on Senna alexandrina Mill., folium and fructus (Revision 1)
• EMA/HMPC Assessment Report on Senna alexandrina
• Commission E Monograph: Sennae folium; Sennae fructus
• ESCOP Monograph: Sennae folium; Sennae fructus
• Expanded Commission E: Senna leaf (HerbalGram)
• LiverTox (NIH): Senna entry
• Review article: Do stimulant laxatives damage the gut? A critical analysis of current knowledge. PMC 2024
• StatPearls: Melanosis Coli
• Wald A. Is chronic use of stimulant laxatives harmful to the colon? J Clin Gastroenterol. 2003;36(5):386-389
• Senna: Drugs.com comprehensive monograph

Connections

• Compare with Psyllium for constipation — contrasting mechanisms (stimulant vs bulk-forming)
• Compare with Linseed/Flaxseed as another constipation remedy with different mechanism
• The electrolyte imbalance concern with senna is relevant when combined with licorice in STW 5/Iberogast
• Senna represents the most pharmacologically potent laxative in this collection, with the most restrictive safety limitations