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Western herbalism

Cascara sagradaRhamnus purshiana (Frangula purshiana)

A stimulant-laxative bark. FDA removed it from OTC laxative products in 2002; EMA limits use to 1 week and found no controlled trials of cascara alone.

Botanical name
Rhamnus purshiana (Frangula purshiana)
Part used
aged bark
Also called
Cascara, Sacred bark, Chittem bark, California buckthorn bark
Used in
Western herbalism
Taken for
Constipation
Sold as
capsules, tablets, liquid extract, bark for tea

Cascara sagrada, the plant and the part used

Cascara sagrada, Spanish for “sacred bark,” is the dried bark of Rhamnus purshiana (also written Frangula purshiana), a tree native to the Pacific coast of North America from British Columbia to California. EMA’s assessment report explains that the historic drug is the aged bark, stored before use, and that a related cascara, probably Rhamnus californica, was known to early Mexican and Spanish priests of California; R. purshiana itself was not described until 1805, and its bark entered medicine in 1877.

The bark is sold as capsules, tablets, liquid extracts, and a loose bark for tea, often in blends with other herbs. The active constituents are cascarosides, which make up 60 to 70 percent of the bark’s hydroxyanthracene complex according to EMA, alongside aloins and related compounds.

In the United States the regulatory picture is specific. A 2002 FDA final rule declared cascara sagrada ingredients, including bark, extract, fluidextract and casanthranol, not generally recognized as safe and effective for over-the-counter laxative use. The rule’s text covers OTC drug products labeled for laxative use, those with a Drug Facts panel; it does not itself address products sold as dietary supplements.

Traditional uses, in their own terms

Western herbalism

EMA’s review of the literature records that cascara bark entered medicine in 1877 and that its use as a purgative in Europe is known since 1880, with the British Pharmaceutical Codex (1911), Hagers Handbuch (1927) and Martindale (1967) all listing such use. The American Eclectic Materia Medica of 1922 describes it for sick headache from atonic sluggishness of the bowels. On this record EMA treats cascara as a stimulant laxative for short-term use in occasional constipation. Cascara is a Western herbal laxative; we found no Ayurvedic or Chinese tradition in the sources that uses this particular bark.

Compounds, and what the laboratory says about them

The therapeutic constituents are cascarosides A to F, mixed anthrone glycosides, which together form 60 to 70 percent of the hydroxyanthracene complex of the dried bark, with 10 to 30 percent aloins. Gut bacteria hydrolyze cascarosides in the colon to active anthrone metabolites; in intestinal extract from germ-free rats the cascarosides were not metabolized, which points to the role of bacteria. In animal and tissue work these metabolites increase colonic fluid and motility. Anthraquinone relatives, including emodin and aloe-emodin, showed genotoxic activity in laboratory tests, which is the reason regulators are cautious about long use. These findings are laboratory and animal results, not human trial outcomes.

Trials in people, with the numbers

EMA’s assessment report is blunt about the clinical record. There are limited clinical studies with cascara bark as a single active ingredient, and the efficacy is assumed from documented medicinal use and from the well-established class of stimulant laxatives such as senna and aloe. The only clinical investigations of cascara as a laxative evaluate it in combination preparations, and there are no controlled clinical studies available. In one set of bowel-cleansing studies a cascara preparation combined with magnesium sulfate was inferior to a polyethylene glycol and electrolyte solution, so the effect of cascara alone could not be assessed. We could find no dose-finding study.

For the class, senna has randomized evidence. A 28-day trial in 90 adults found a 69.2 percent response on senna versus 11.7 percent on placebo, and a systematic review graded senna A for chronic constipation. Cascara contains the same kind of anthranoid, but no published data show that it behaves the same way at a given dose.

On long-term safety the evidence is mixed and comes from anthranoid laxatives as a group. A prospective case-control study of 554 people found no link between anthranoid laxative use and colorectal adenomas or cancer (odds ratio 1.0 for both). An endoscopy study found pseudomelanosis coli more often in people with colorectal cancer (relative risk 3.04). A 2024 review of 43 publications on stimulant laxatives found no convincing evidence of colon cancer.

One cascara-specific case report describes a severe cholestatic hepatitis in a 48-year-old man three days after he started 425 mg capsules of aged bark three times daily (about 21 mg cascaroside each); jaundice and ascites resolved over three months.

StudyDoseWhat it found
Case report of cholestatic hepatitis after cascara capsules (cascara-specific) PMID 11151906425 mg aged bark capsule, three times daily for 3 daysSevere cholestatic hepatitis, ascites; resolved over 3 months
Prospective case-control study, 202 colorectal carcinoma, 114 adenoma, 238 controls (all anthranoid laxatives) PMID 10764708Anthranoid laxative historyNo risk for adenomas (OR 1.0) or carcinomas (OR 1.0)
Prospective endoscopy study, 1,095 patients (anthranoid laxatives) PMID 8174962Chronic use over 9 to 12 monthsPseudomelanosis coli 6.9% normal, 9.8% adenoma, 18.6% carcinoma; relative risk 3.04
Review of 43 publications on stimulant laxative safety (senna and diphenylmethanes) PMID 38887508VariousNo convincing evidence of colon cancer; high-dose structural changes reversible

The doses on record

No trial has set a dose of cascara. The EMA monograph (in its revised version) lists, for adolescents and adults, preparations equivalent to 10 to 30 mg of hydroxyanthracene derivatives, calculated as cascaroside A, once daily at night, with the correct dose described as the smallest required to produce a comfortable soft-formed stool. A herbal tea is prepared from a standardized amount of comminuted bark in 150 ml of boiling water. Duration is not to exceed one week, and usually two to three doses in that week are sufficient. The case report above involved 425 mg capsules of aged bark with 5 percent cascaroside potency.

None of this is a dose recommendation. It is what the literature used, set down so a label can be compared with it; a pharmacist or clinician decides what applies to you.

The safety record

EMA lists intestinal obstruction and stenosis, atony, appendicitis, inflammatory bowel disease, abdominal pain of unknown origin, severe dehydration, and age under 12 as contraindications, and says use in pregnancy and lactation is contraindicated because of experimental genotoxic risk of anthranoids such as emodin and aloe-emodin. It warns that long-term use of stimulant laxatives may lead to impaired intestinal function and dependence, that patients with kidney disorders should be aware of electrolyte imbalance, and that incontinent adults need pads changed more often to prevent skin damage.

Hepatotoxicity has been reported with chronic overdose, and a cascara-specific case of cholestatic hepatitis is documented. The 2002 FDA rule was based on the absence of carcinogenicity, genotoxicity and mutagenicity data that the agency had requested; it did not report harm in people.

Medicines it can interact with

The EMA monograph says that low potassium from long-term laxative abuse potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicines. Concomitant use with diuretics, adrenocorticosteroids and licorice root may enhance potassium loss, and patients taking those products, or medicines that prolong the QT interval, are told to consult a doctor first. The case report of hepatitis involved a patient also taking amitriptyline, cimetidine and baclofen, so the contribution of those medicines could not be separated.

Where cascara sagrada turns up in the catalog

Cascara sagrada appears on the labels below, alone or inside a blend; each product page gives the printed amount, the evidence for that product and the review picture.

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 Bio Cleanse Herbal Detox Kit 3.7 out of 5 from 263 ratings from Amazon · $10.33 per day over the 9-day course at the Amazon price ($9.22 at the brand price); it is a course, not a daily supplement

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Read next

Ayurvedic / Western Senna Senna alexandrina (Cassia senna, Cassia angustifolia) TCM / Western Aloe vera Aloe vera (L.) Burm.f. (Aloe barbadensis Miller) TCM / Western Rhubarb root Rheum palmatum; Rheum officinale Ayurvedic / Western Psyllium Plantago ovata Western Yellow dock Rumex crispus

What people want to know

Why did FDA remove cascara from OTC laxatives?

In 2002 FDA ruled that aloe and cascara sagrada ingredients in OTC laxative products were not generally recognized as safe and effective. The agency had asked for genotoxicity, mutagenicity and carcinogenicity data and received none for these ingredients. It said they should be eliminated from OTC laxative drug products.

Is a cascara supplement the same as an OTC drug?

Not in the way the label is regulated. A product with a Drug Facts panel is an OTC drug under the drug rules, and the 2002 rule concerns products labeled for OTC laxative use. The rule's text does not itself address herbal products sold as dietary supplements.

Has cascara been tested in clinical trials?

EMA found no controlled clinical studies of cascara alone. The only studies used it in combination products, and the efficacy is inferred from long use and from the class of stimulant laxatives.

How long can it be used according to the monograph?

EMA's revised monograph says not to use for more than one week, and notes that two to three doses in that week usually suffice. It warns that long-term use of stimulant laxatives may lead to impaired bowel function and dependence.

Does cascara cause melanosis coli?

Melanosis coli, a brown discoloration of the colon lining, is associated with long-term anthranoid laxative use, which includes cascara, senna and aloe. A prospective case-control study found no link between anthranoid use and colorectal adenoma or cancer, while an earlier endoscopy study found a higher rate of melanosis in people with cancer.

Sources