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Traditional Chinese medicine · Western herbalism

Rhubarb rootRheum palmatum; Rheum officinale

Rhubarb root (da huang) is a stimulant laxative; a 42-person trial used 12.5 or 25 mg of rhein a day for 30 days, while the EU monograph caps use at 1 week.

Botanical name
Rheum palmatum; Rheum officinale
Part used
root and rhizome, dried (not the edible stalk)
Also called
pinyin Da huang (大黄); Chinese rhubarb, Rhei radix, Rhei radix et rhizoma, Dai-o (Japanese)
Used in
Traditional Chinese medicine, Western herbalism
Taken for
Constipation, Liver and bile
Sold as
decoction, powder, tablets, granule extract, patent medicine, dried slices

What is meant by rhubarb root

Rhubarb root, or da huang in Chinese, is the dried root and rhizome of Rheum palmatum and R. officinale, and in China of the related R. tanguticum. It is not the edible garden rhubarb stalk. A review of the herb in the American Journal of Chinese Medicine says it is in the 2020 Chinese Pharmacopoeia, is one of the most commonly used Chinese medicines, and contains more than 170 compounds, with anthraquinones and anthrones as the major group, along with stilbenes, chromones, flavonoids and tannins.

The anthranoid compounds are what make it a laxative. The European monograph explains that the sennosides and related glycosides are not absorbed in the upper gut: bacteria in the large intestine convert them into active anthrones, which speed colonic movement and draw water and electrolytes into the bowel, with the bowel opening 8 to 12 hours later. The monograph classes it as a contact laxative. It is prepared raw, steamed with wine or charred, and is taken as a decoction, a powder, a granule extract, in tablets and in patent medicines.

In the traditions

Traditional Chinese medicine (about TCM)

Da huang is bitter and cold in the materia medica, entering the spleen, stomach, large intestine, liver and pericardium channels, with the actions of draining downward accumulations, clearing heat and draining fire, cooling blood, resolving toxicity and invigorating blood to dispel stasis. For the gut the tradition uses it for what it calls heat and dryness accumulated in the intestines: hard stools, abdominal fullness and pain, and feverishness, which is the picture Da Cheng Qi Tang is written for, where it is paired with mirabilite, magnolia bark and immature bitter orange. The same texts use it in damp-heat jaundice. Rhubarb meant for purging is conventionally cooked briefly or added near the end of a decoction. Heat and dryness in the intestines is the texts’ description and not a finding.

Western herbalism

Western herbal medicine knows rhubarb root as a stimulant laxative of the anthranoid group. The European Union herbal monograph, which refers to the European Pharmacopoeia monograph for the material, accepts it as a well-established-use herbal medicinal product for short-term use in cases of occasional constipation, standardized to hydroxyanthracene derivatives calculated as rhein. The monograph limits use to one week, tells users to try diet change or bulk-forming agents first, and contraindicates use in pregnancy, lactation and under 12 years.

What the plant contains

The laxative compounds are anthraquinones and anthrones, among them rhein, emodin and aloe-emodin, partly bound as glycosides of the sennoside type. After a dose, rhein, emodin and traces of chrysophanol appear in human urine, the EU monograph reports. In animal studies, a total anthraquinone extract caused kidney effects in rats at 4,500 mg per kg a day for 13 weeks, an ethanolic root extract was weakly mutagenic in one bacterial test, and several hydroxyanthracene derivatives were genotoxic in laboratory systems though not shown in living animals. These are laboratory and animal findings.

What has been tested in people

Rhubarb has real single-herb human data, unlike most of the herbs on this list, though the trials are small or from China.

For constipation, a double-blind, placebo-controlled trial randomized 42 middle-aged volunteers, 14 per group, to rhubarb extract delivering 12.5 or 25 mg of rhein a day, or placebo, for 30 days. Stool frequency and consistency, and perceived transit, improved in both extract groups compared with placebo, with a larger effect at the higher dose, and blood potassium did not change. The trial studied infrequent bowel movements and not severe constipation, and the sample was 95 percent women.

For pancreatitis and the bowel, Chinese trials use crude rhubarb as an add-on. A meta-analysis of 19 trials with 1,161 patients found that adding crude rhubarb to somatostatin cut total complications (RR 0.55, 95% CI 0.41 to 0.73) and hospital stay (6.70 days shorter), with no significant difference in mortality (RR 0.61, 0.34 to 1.12); a second pooled 16 trials in 912 people with severe disease, and the authors warned of publication bias. In ulcerative colitis, a meta-analysis of 30 studies with 2,475 patients found rhubarb-based therapy, oral or by enema, improved efficacy and recurrence, pooling studies of mixed design; note that the EU monograph contraindicates oral rhubarb in ulcerative colitis, a different context from these trials. Da Cheng Qi Tang, which contains rhubarb, is covered on the magnolia bark page.

Not tested: rhubarb against standard laxatives, long-term outcomes, and any use in children.

StudyDoseWhat it found
Double-blind placebo-controlled RCT, 42 randomized middle-aged adults with infrequent bowel movements (rhubarb extract) PMID 36499011Extract giving 12.5 or 25 mg of rhein a day for 30 daysStool frequency and consistency better than placebo in both doses; blood potassium unchanged
Meta-analysis of 19 RCTs, 1,161 patients with acute pancreatitis (crude rhubarb added to somatostatin) PMID 27693773Crude rhubarb as add-onComplications RR 0.55 (0.41 to 0.73); hospital stay 6.70 days shorter; mortality RR 0.61 (0.34 to 1.12), not significant
Meta-analysis of 16 RCTs, 912 patients with severe acute pancreatitis (rhubarb plus trypsin inhibitor) PMID 29672966Rhubarb added to standard careLower mortality, shorter hospital stay and pain relief time; publication bias noted; no serious adverse events
Meta-analysis of 30 studies, 2,475 patients with ulcerative colitis (rhubarb-based therapy, oral or enema) PMID 36339579Oral or enema; course length varied by studyHigher efficacy and lower recurrence; better than 5-ASA or sulfasalazine alone; no significant side effects reported
Meta-analysis of 60 RCTs, 6,095 patients with intestinal obstruction (Da Cheng Qi Tang, contains rhubarb) PMID 25392589Decoction, alone or added to conservative therapyAdd-on response RR 1.25 (1.20 to 1.30); time to first flatus SMD -2.09

Doses used in trials and traditional preparations

The EU monograph gives a preparation equivalent to 20 to 30 mg of hydroxyanthracene derivatives, calculated as rhein, once a day at night, as the smallest dose that gives a soft stool, or a tea of not more than 30 mg in 150 ml of boiling water, and no more than one week of use. The 42-person trial used 12.5 or 25 mg of rhein a day for 30 days, which is longer than the monograph allows. The traditional decoction is dosed in grams of the root and differs by formula; purgative use is a short cook or a late addition. In the pancreatitis trials the crude root was given as an add-on to standard treatment in hospital.

Treat these figures as a record of what was studied. Whether any amount of rhubarb root suits a particular person is a question for a clinician or pharmacist who knows their history.

Safety

The EU monograph lists abdominal pain, spasm and liquid stools as the common effects, pseudomelanosis coli (pigment in the bowel lining, which recedes after stopping) with chronic use, yellow or red-brown urine, and, after long use, water and electrolyte loss that may cause protein or blood in the urine. Overdose causes griping pain and severe diarrhea with loss of fluid and potassium; chronic overdose of anthranoid products may lead to toxic hepatitis. It contraindicates use in pregnancy, lactation, under 12, intestinal obstruction, appendicitis, inflammatory bowel disease, abdominal pain of unknown origin and severe dehydration. In rats, total rhubarb anthraquinones damaged the kidney at the highest dose (4,500 mg per kg for 13 weeks), and the monograph reports no further toxicology data for the root itself.

Drug interactions

The mechanism is potassium. The EU monograph says low potassium from long-term laxative use strengthens the action of cardiac glycosides and interacts with antiarrhythmic medicines, and that concomitant use with diuretics, corticosteroids and liquorice root may increase potassium loss. It tells patients taking cardiac glycosides, antiarrhythmics, QT-prolonging medicines, diuretics, corticosteroids or liquorice to consult a doctor before taking rhubarb, and notes that people with kidney disorders should be aware of possible electrolyte imbalance. The 42-person trial found no change in potassium over 30 days at either dose.

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Related herbs

Ayurvedic / Western Senna Senna alexandrina (Cassia senna, Cassia angustifolia) Western Cascara sagrada Rhamnus purshiana (Frangula purshiana) TCM Magnolia bark Magnolia officinalis Ayurvedic / TCM / Western Licorice Glycyrrhiza glabra TCM / Western Aloe vera Aloe vera (L.) Burm.f. (Aloe barbadensis Miller)

Questions people ask

Is rhubarb root the same as garden rhubarb?

No. The medicinal drug is the dried root and rhizome of Rheum palmatum or R. officinale, not the edible stalk.

How does rhubarb root work as a laxative?

Its sennoside-type glycosides pass through the upper gut unabsorbed. Bacteria in the colon convert them to active anthrones, which speed transit and draw in water and electrolytes, with a bowel movement after about 8 to 12 hours.

How long is it meant to be used?

The European Union monograph limits use to one week and says to try diet change or bulk-forming agents first. The 42-person trial used 30 days at 12.5 or 25 mg of rhein a day.

Does rhubarb help acute pancreatitis?

A meta-analysis of 19 trials with 1,161 patients found fewer complications and shorter hospital stay when crude rhubarb was added to somatostatin, with no significant difference in mortality. The trials had methodological flaws.

Who is told to avoid it?

The monograph contraindicates use in pregnancy, lactation, children under 12, bowel obstruction, appendicitis, Crohn’s disease and ulcerative colitis, and severe dehydration. It also flags heart medicines and diuretics.

Sources