Senna

Senna entered medicine through the Arabian physicians Serapion and Mesue. Mesue preferred the pods, thinking them stronger; they are in fact milder, and cause less griping ^{27Reference 27Grieve · 1931A Modern Herbal — SennaView study →}.

In European practice senna became a standard purgative for habitual constipation. It was given with cloves, ginger, cinnamon or other aromatics to correct its nauseating taste and griping. The official senna tea was infused with sliced ginger, and the United States Pharmacopoeia preferred coriander ^{27Reference 27Grieve · 1931A Modern Herbal — SennaView study →}.

The “black draught” of older pharmacy combined senna with gentian and an aromatic such as cardamom, coriander or Seville orange peel ^{27Reference 27Grieve · 1931A Modern Herbal — SennaView study →}.

Western herbal medicine still uses senna as a short-term remedy for constipation ^{28Reference 28Hoffmann · 2003Medical herbalism: The science and practice of herbal medicine}.

Senna leaf is fan xie ye (番泻叶); fan marks it as a foreign, imported drug.

It is classed as a purgative that drains downward. It drains heat, removes stagnation, promotes defecation and urination, and relaxes the bowels ^{25,26,29Reference 25Yang et al. · 2013Introduction to Chinese materia medica (3rd ed.). (PgReference 26Wu · 2005An illustrated Chinese materia medicaReference 29Hempen et al. · 2009A Materia Medica for Chinese Medicine}.

It is given for heat accumulation with constipation and abdominal pain, and for oedema, fullness and distension ^{25,29Reference 25Yang et al. · 2013Introduction to Chinese materia medica (3rd ed.). (PgReference 29Hempen et al. · 2009A Materia Medica for Chinese Medicine}.

To break up stagnation it is paired with zhi shi and hou po. For constipation from heat accumulating in the intestines, it is paired with huo xiang and mu xiang ^{29Reference 29Hempen et al. · 2009A Materia Medica for Chinese Medicine}.

Senna is used for constipation in Ayurvedic medicine ^{30Reference 30Das et al. · 2003A handbook of medicinal plants}.

In Pakistan the dried leaves are used as a purgative and for biliousness, gout, rheumatism, skin diseases and intestinal worms. The pods are also taken as a purgative ^{34Reference 34AliAli, S. I. (n.d.). Cassia senna Linnaeus (syn. Cassia angustifolia Vahl) — species description, distribution and uses — flora. Flora of Pakistan (Caesalpiniaceae). http://www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=250063485View study →}.

The first double-blind, placebo-controlled trial to compare a stimulant with an osmotic laxative for chronic idiopathic constipation enrolled 90 patients. Over 28 days, senna 1.0 g and magnesium oxide 1.5 g daily improved overall symptoms in 69.2% and 68.3% of patients, against 11.7% on placebo, with no severe treatment-related adverse events ^{1Reference 1Morishita et al. · 2021RCTSenna versus magnesium oxide for the treatment of chronic constipation — randomised, placebo-controlled trialView study →}.

A 2005 systematic review found few good-quality trials of senna ^{2Reference 2Ramkumar et al. · 2005Systematic reviewEfficacy and safety of traditional medical therapies for chronic constipation — systematic reviewView study →}. By 2021, an updated review of over-the-counter therapies gave senna a grade A recommendation as a first-line laxative, and the 2023 AGA-ACG guideline makes a conditional recommendation for it ^{3,4Reference 3Chang et al. · 2023AGA-ACG clinical practice guideline: pharmacological management of chronic idiopathic constipation — practice guidelineView study →Reference 4Rao et al. · 2021Systematic reviewEfficacy and safety of over-the-counter therapies for chronic constipation — systematic reviewView study →}.

In 77 long-stay elderly patients, a senna-fibre combination gave more frequent bowel movements than lactulose, at lower cost ^{7Reference 7Passmore et al. · 1993RCTChronic constipation in long stay elderly patients: comparison of lactulose and a senna-fibre combination — randomised controlled trialView study →}.

In a crossover trial in 21 children, lactulose gave more days of normal stools, and side effects were much more frequent on senna ^{8Reference 8Perkin · 1977RCTConstipation in childhood: a controlled comparison between lactulose and standardised senna — randomised controlled trialView study →}. A Cochrane review of childhood constipation rated the overall evidence for laxatives as low or very low quality ^{6Reference 6Gordon et al. · 2016Systematic reviewOsmotic and stimulant laxatives for the management of childhood constipation — systematic reviewView study →}.

The sennosides are the active fraction. Cramping and liquid stools usually mean the dose is too high ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

In a randomised, endoscopist-blinded study of 474 outpatients, a split high-dose sennoside solution (1,000 mg) cleaned the bowel better than 4 L of split-dose polyethylene glycol (PEG): preparation was adequate in 89.9% versus 73.8% ^{9Reference 9Coskun et al. · 2020RCTPolyethylene glycol versus split high-dose senna for bowel preparation — randomised controlled trialView study →}. Nausea and vomiting were less frequent on senna, and abdominal pain more frequent (70.9% versus 43%) ^{9Reference 9Coskun et al. · 2020RCTPolyethylene glycol versus split high-dose senna for bowel preparation — randomised controlled trialView study →}.

In 382 patients, low-volume PEG plus senna matched high-volume PEG (adequate preparation in 71.9% versus 69.4%), with fewer side effects ^{10Reference 10Sadeghi et al. · 2022RCTLow volume polyethylene glycol combined with senna versus high volume polyethylene glycol for bowel preparation — randomised controlled trialView study →}.

In children, a meta-analysis of three trials (318 patients) favoured PEG over senna for preparation quality, and PEG caused less pain. The certainty of the evidence was low to moderate ^{11Reference 11Watanabe et al. · 2021Meta-analysisPolyethylene glycol versus senna for bowel preparation for colonoscopy in children — systematic review and meta-analysisView study →}.

Gap: doses and timing differ between protocols, and the only paediatric meta-analysis favours PEG ^{11Reference 11Watanabe et al. · 2021Meta-analysisPolyethylene glycol versus senna for bowel preparation for colonoscopy in children — systematic review and meta-analysisView study →}.

A Cochrane review of laxatives for constipation in palliative care included trials of senna, lactulose and other laxatives. It found the evidence comparing them inconclusive, because there were too few trials ^{5Reference 5Candy et al. · 2011Systematic reviewLaxatives or methylnaltrexone for the management of constipation in palliative care patients — systematic reviewView study →}.

In 107 patients after rotator-cuff surgery, neither docusate nor senna reduced postoperative constipation compared with no laxative: 71.4%, 66.7% and 64.3% of patients were constipated ^{12Reference 12Weekes et al. · 2021RCTEfficacy of docusate sodium and senna glycoside for constipation after rotator cuff repair — randomised controlled trialView study →}.

Gap: there is no placebo-controlled trial of senna alone in opioid-induced constipation.

Leaf extracts of Cassia angustifolia scavenged DPPH radicals in vitro (IC50 2.41 μg/mL) ^{22Reference 22Ahmed et al. · 2016In vitroPharmacologically active flavonoids from the anticancer, antioxidant and antimicrobial extracts of Cassia angustifolia Vahl — in vitroView study →}.

In rats with carbon-tetrachloride liver injury, a methanol fraction of the leaf reduced lipid peroxidation and protein carbonyls in the liver ^{21Reference 21Bellassoued et al. · 2021AnimalAntioxidant and hepatopreventive effects of Cassia angustifolia extract against carbon tetrachloride-induced hepatotoxicity in rats — animal modelView study →}.

Gap: there are no human antioxidant data, and the extracts tested are not the standardised laxative preparations.

In rats, pretreatment with a methanol fraction of Cassia angustifolia leaf reduced carbon-tetrachloride-induced rises in liver enzymes, cholesterol, triglycerides and LDL, and largely prevented liver lesions ^{21Reference 21Bellassoued et al. · 2021AnimalAntioxidant and hepatopreventive effects of Cassia angustifolia extract against carbon tetrachloride-induced hepatotoxicity in rats — animal modelView study →}.

A separate study found a standardised senna extract was not hepatotoxic in rats at doses higher than those used in people. It was toxic to liver cells in culture only at concentrations far above those reached in humans ^{18Reference 18Vitalone et al. · 2011In vitroCassia angustifolia extract is not hepatotoxic in an in vitro and in vivo study — animal modelView study →}.

The EU herbal monograph notes that chronic overdose of anthranoid laxatives may lead to toxic hepatitis ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

Gap: the evidence is one rodent efficacy study; there are no human data.

Leaf extracts of Cassia angustifolia inhibited the growth of Enterobacter cloacae, Pseudomonas aeruginosa, Serratia marcescens and Salmonella typhi in culture ^{22Reference 22Ahmed et al. · 2016In vitroPharmacologically active flavonoids from the anticancer, antioxidant and antimicrobial extracts of Cassia angustifolia Vahl — in vitroView study →}.

A leaf extract killed Acanthamoeba triangularis trophozoites at micromolar levels, forming pores in their membranes and rupturing them ^{23Reference 23Boonhok et al. · 2021In vitroAmoebicidal activity of Cassia angustifolia extract against Acanthamoeba triangularis — in vitroView study →}.

Gap: culture work only, with no animal or human data.

Bioactivity-guided fractionation of Cassia angustifolia leaf extracts isolated three flavonoids — quercimeritrin, scutellarein and rutin. They were active against MCF-7 breast, HeLa cervical and Hep2 cancer cells, and less toxic to normal HCEC cells ^{22Reference 22Ahmed et al. · 2016In vitroPharmacologically active flavonoids from the anticancer, antioxidant and antimicrobial extracts of Cassia angustifolia Vahl — in vitroView study →}.

Gap: in vitro only, on isolated compounds; there are no animal or human data.

Short courses only. Long-term use of stimulant laxatives can impair bowel function and lead to dependence on laxatives. If a laxative is needed every day, the cause of the constipation should be looked into. Senna is for use after a change of diet or a bulk-forming laxative has not worked ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

Common effects. Senna can cause abdominal pain, spasm and liquid stools, especially in people with an irritable bowel; these usually mean the dose is too high. Hypersensitivity reactions such as itching, hives and rash can occur. Urine may turn yellow or red-brown, which is not clinically significant ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

Long-term use. Prolonged use can upset the balance of water and electrolytes, and may cause protein and blood in the urine. It can also pigment the colon lining (pseudomelanosis coli), which usually fades once senna is stopped ^{16,33Reference 16van Gorkom et al. · 1999ReviewReview article: anthranoid laxatives and their potential carcinogenic effects — reviewView study →Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}. People with kidney disease should be aware of the risk of electrolyte imbalance ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

Colon damage and cancer. A 1999 review linked pseudomelanosis coli to colorectal cancer and advised against long-term use ^{16Reference 16van Gorkom et al. · 1999ReviewReview article: anthranoid laxatives and their potential carcinogenic effects — reviewView study →}. Later work has not borne this out. A case-control study using aberrant crypt foci found no causal link between anthranoid laxatives and colon cancer ^{17Reference 17Nascimbeni et al. · 2002ObservationalConstipation, anthranoid laxatives, melanosis coli, and colon cancer: a risk assessment using aberrant crypt foci — observational studyView study →}. Reviews found no convincing evidence of damage to the bowel’s nerves or muscle, no tumours in rats given senna for two years at up to 300 mg/kg/day, and no genotoxic risk for patients ^{14,15Reference 14Whorwell et al. · 2024ReviewReview article: do stimulant laxatives damage the gut? A critical analysis of current knowledge — reviewView study →Reference 15Morales et al. · 2009ReviewIs senna laxative use associated with cathartic colon, genotoxicity, or carcinogenicity? — reviewView study →}. Structural changes seen at very high doses are reversible ^{14Reference 14Whorwell et al. · 2024ReviewReview article: do stimulant laxatives damage the gut? A critical analysis of current knowledge — reviewView study →}.

Who should not take it. Senna is contraindicated in bowel obstruction or narrowing, bowel atony, appendicitis, inflammatory bowel disease (Crohn’s disease, ulcerative colitis), abdominal pain of unknown cause, and severe dehydration ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}. It should not be taken with faecal impaction, or with unexplained abdominal pain, nausea or vomiting, which can signal a blocked bowel ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}. Older texts also advise against it with inflammation of the digestive tract, haemorrhoids and rectal prolapse ^{27Reference 27Grieve · 1931A Modern Herbal — SennaView study →}.

Interactions. Potassium lost through long-term use strengthens the effect of cardiac glycosides such as digoxin and interacts with antiarrhythmic drugs. Diuretics, corticosteroids and liquorice root add to the potassium loss ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

Children. The EU herbal monograph does not allow senna under 12 years ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}. Where it is used in children, a blistering rash in the nappy area can follow high doses with long contact between stool and skin. At one centre, 17 of 640 children (2.2%) developed blisters, on higher doses than those who did not (median 60 mg/day) ^{32Reference 32Vilanova-Sanchez et al. · 2018ReviewAre senna based laxatives safe when used as long term treatment for constipation in children? — retrospective reviewView study →}. The same care applies to incontinent adults: pads should be changed often ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.

Overdose. Overdose causes griping pain and severe diarrhoea, with loss of fluid and electrolytes. Chronic overdose of anthranoid laxatives may lead to toxic hepatitis ^{33Reference 33European Medicines Agency · 2018ReviewEuropean Union herbal monograph on Senna alexandrina Mill. (Cassia senna L.; Cassia angustifolia Vahl), folium — regulatory monographView study →}.