Cascara Sagrada

What is Cascara Sagrada?

Cascara sagrada is bark that USP requires be collected not less than one year before use, harvested from Frangula purshiana (DC.) A.Gray ex J.G.Cooper, a Rhamnaceae tree of the Pacific Northwest. The monograph is explicit: the article is the dried bark, it must yield not less than 7.0 percent total hydroxyanthracene derivatives calculated as cascaroside A on the dried basis, and not less than 60 percent of those derivatives must be cascarosides. The aging note is one sentence long, and it is the reason the bark is tolerable at all.

The tree grows from southern British Columbia to central California and east into northwestern Montana, reaching 4.5 to 12 meters tall with a trunk 20 to 50 cm across. Bark is peeled in the dry season, roughly mid-April through late August, and about 5 million pounds are reported harvested annually for the botanical trade. Fresh bark loses about 50 percent of its weight in drying, then sits one to three years before it is fit to sell. Most labels still carry the older name Rhamnus purshiana DC., as does the USP monograph.

Common Names

• Cascara sagrada, from the Spanish for sacred bark

• Cascara buckthorn, California buckthorn

• Chittam bark, chittem stick, chitticum stick

• Bearberry, bearwood

• Rhamni purshianae cortex, the pharmacopoeial Latin used by the EMA

Primary Active Compounds

• Cascarosides A, B, C and D, the four principal glycosides. A and B are stereoisomer pairs derived from barbaloin and carry both an O-glycosidic and a C-glycosidic linkage; C and D derive from chrysaloin.

• Barbaloin (aloin) and chrysaloin, the C-glycosides left after partial hydrolysis

• Aloe-emodin, emodin and chrysophanol, as O-glycosides and free aglycones

• Anthrones and dianthrones, including the compounds that make unaged bark violently emetic

• Total anthracene derivatives run about 6 to 9 percent of the dried bark

Key Note

Potency is not evenly distributed across that chemistry. The intact cascarosides are the most active laxative fraction, the aloins are weaker, and the free anthraquinones and dimers have little purgative activity. A bark testing at 9 percent total anthracenes with only 30 percent cascarosides is weaker and less predictable than one testing at 7 percent with 70 percent cascarosides, which is why the pharmacopoeial assay is written as cascaroside A.

Cascara sagrada is a stimulant laxative with a long commercial history, a short list of controlled human trials, and a regulatory record more interesting than its evidence base.

Primary Functions & Benefits

Cascara sagrada does one thing reliably. It produces a bowel movement, typically 8 to 12 hours after an oral dose, by acting directly on the colon.

Stimulant laxation

Colonic bacteria convert the unabsorbed cascarosides into active anthrones, which increase propulsive motility and shift the colon from net fluid absorption toward net secretion. Stool volume rises and transit time falls.

Short-term relief of occasional constipation

The only indication accepted by any current regulatory body. The EMA’s HMPC lists cascara under well-established use for short-term relief of occasional constipation in adults and adolescents over 12, with a ceiling of one week. It was also used historically in pre-procedure bowel clearing, but polyethylene glycol and sodium picosulfate displaced it.

What it does not do

Cascara sagrada does not detoxify, does not cleanse the liver, does not treat parasites, and does not produce weight loss beyond transient loss of stool water and electrolytes. It has no evidence base as a tonic, a daily digestive aid, or part of a multi-week cleanse. Marketing that positions it in those roles describes a use that no pharmacopoeia, no monograph and no controlled trial supports.

Forms & Standardization

Standardization for cascara is unusually well defined on paper and unusually loose in the US supplement aisle.

Dried bark powder, capsules

The most common retail form, typically 425 mg or 450 mg of dried bark per capsule. At the USP floor of 7.0 percent, a 425 mg capsule carries roughly 30 mg of hydroxyanthracenes, the top of the European single-dose range; at 9 percent, roughly 38 mg, above it. Most US labels state milligrams of bark and nothing about anthracene content, so the delivered dose can vary by a factor of two between bottles of the same stated strength.

Standardized dry extract

European Pharmacopoeia monograph 01/2008:1844 specifies a nominal hydroxyanthracene glycoside content of 8.0 to 25.0 percent m/m as cascaroside A, assayed at 90 to 110 percent of that nominal figure, with not less than 60 percent of the glycosides being cascarosides, extracted in boiling water or a solvent at least as strong as 60 percent V/V ethanol. This is the form where a stated dose means something.

Fluidextract, aromatic fluidextract and tea

Traditional liquids are dosed at roughly 2 to 6 mL, and the aromatic version was one of the five cascara articles FDA delisted by name in 2002. Both have largely left US retail. The EMA monograph permits comminuted bark supplying at most 30 mg hydroxyanthracene derivatives per 150 mL of boiling water. Home-brewed bark tea has no dose control at all.

Combination products

Cascara appears in cleanse blends alongside senna (Senna alexandrina), aloe latex, rhubarb root and buckthorn. Stacking two or three anthranoids multiplies the anthracene load while each ingredient looks modest on the panel.

What standardization to look for

A stated percentage of hydroxyanthracene derivatives as cascaroside A, with the cascaroside fraction also stated. Anything else is not standardization, and a milligram figure for bark alone is a weight rather than a potency.

Food Sources

None. Cascara sagrada is a bark, not a food, and it has no dietary occurrence.

One naming collision is worth knowing. “Cascara” is also the trade name for the dried husk of the coffee cherry, Coffea arabica L., assessed by EFSA as an EU novel food. Coffee cherry cascara contains caffeine, no anthranoids and no laxative action. If you buy loose “cascara” from a coffee roaster, you are buying coffee fruit.

Who Should Take Cascara Sagrada

The group with a defensible reason to use it is narrow.

Adults with occasional constipation who have already tried the first-line options

Fiber, fluid, movement and an osmotic agent such as polyethylene glycol are the standard first steps. Osmotic laxatives have a larger and more recent evidence base than anthranoids, with no dependence concern attached. Cascara is a second or third option for someone who has worked through those and wants a short, defined course.

Adults who prefer a stimulant and tolerate it

Stimulants act faster and more predictably than bulk agents in some people. If a stimulant is the right class, cascara is one option within it, alongside bisacodyl and senna, both of which have more human trial data.

Adults over 12 who can commit to a one-week ceiling

The EMA monograph contraindicates children under 12, and no pediatric dosing exists anywhere. The duration limit matters more. Anyone who anticipates needing a laxative for longer than a week needs a workup for the cause, not a longer course of cascara.

Who Should AVOID or Use Caution

Contraindications

• Children under 12 years, per the EMA herbal monograph

• Pregnancy at any stage, excluded by the EMA monograph on the basis of experimental genotoxicity data for several anthranoids, on top of maternal fluid and electrolyte losses

• Breastfeeding. Rhein, an anthranoid metabolite, is measurable in human milk, and the monographs contraindicate use despite no reported infant laxative effects.

• Intestinal obstruction, stenosis, or ileus

• Acute inflammatory bowel disease, including Crohn’s disease and ulcerative colitis

• Appendicitis or undiagnosed acute abdominal pain

• Severe dehydration with electrolyte depletion

• Known hypersensitivity to the plant or to Rhamnaceae species

Use Caution

• Anyone taking digoxin or another cardiac glycoside. Potassium loss from stimulant laxatives raises cardiac glycoside sensitivity and arrhythmia risk.

• Anyone taking loop or thiazide diuretics, systemic corticosteroids, or licorice root, each of which independently lowers potassium

• Anyone with a history of liver injury from any cause, given the case reports below

• Anyone with chronic kidney disease, where fluid and electrolyte shifts are less well tolerated

• Adults over 65, who lose potassium more readily and are likelier to be on interacting medications

• Anyone with a history of laxative overuse, an eating disorder involving purging, hemorrhoids or anal fissures

Critical Safety Point

Constipation that persists beyond one week, arrives suddenly in an adult over 50, or comes with rectal bleeding, unexplained weight loss or a change in stool caliber is a reason for a colonoscopy, not a stronger laxative. Cascara masks the symptom while the cause goes unexamined. Every monograph on this bark says the same thing: do not treat undiagnosed gastrointestinal complaints with it.

Recommended Dosages

Dosing is one of the few areas where cascara is well specified, because European regulators wrote it down.

Standardized preparations

EMA posology is a single dose equivalent to 10 to 30 mg hydroxyanthracene derivatives, calculated as cascaroside A, once daily at night, individualized to the lowest amount that produces a soft stool. The German Commission E figure is 20 to 30 mg daily on the same basis, with secondary sources citing a limit of about 8 to 10 consecutive days.

Dried bark and capsules

Roughly 1 g of bark per dose in traditional practice. At the USP minimum of 7.0 percent, 1 g carries about 70 mg hydroxyanthracenes, more than double the EMA single-dose ceiling. Retail capsules of 425 mg or 450 mg supply roughly 30 to 40 mg each. Start at one capsule rather than two, and many people need less.

Dry extract

100 to 300 mg per dose is the figure in the older reference literature. With a standardized extract at 8 to 25 percent hydroxyanthracene glycosides, that spans roughly 8 mg to 75 mg, wide enough that the percentage has to be read off the label before the milligram number means anything.

Fluidextract and tea

2 to 6 mL per dose, or comminuted bark supplying not more than 30 mg hydroxyanthracene derivatives in 150 mL of boiling water, once at night.

Duration

Not more than 1 week, and the EMA monograph adds that within that week 2 to 3 doses usually suffice. Commission E is commonly cited as allowing 8 to 10 consecutive days. Beyond that, use requires medical supervision, and beyond 1 to 2 weeks the monographs stop endorsing it.

Timing & Administration

Take it at night, once daily

Both the EMA monograph and conventional practice put the dose at bedtime. The reason is the 8 to 12 hour lag. A dose at 10 p.m. produces an effect between 6 a.m. and 10 a.m., which is when most people would rather have it.

Take it with a full glass of water

Stimulant laxatives increase stool water content, and replacing that fluid matters in older adults.

Do not take it more than once in a 24-hour period

A second dose taken before the first has acted is the most common cause of the cramping and watery diarrhea people report. The lag makes it easy to assume the dose failed when it has not arrived yet.

Space it from other oral medications

Faster transit shortens the absorption window for anything else in the gut. Leave at least 1 to 2 hours, longer for narrow-therapeutic-index drugs.

Skip nights, and do not stack stimulants

2 to 3 doses across a single week, not 7. Daily dosing is where the tolerance pattern starts. Senna, aloe latex, rhubarb, buckthorn and bisacodyl act through overlapping mechanisms, and combining them stacks the effect without the benefit.

Timeline of Effects

The entire safety argument for this bark is built around a time window.

0 to 8 hours: nothing happens, and that is expected

The cascarosides are not absorbed in the stomach or small intestine and are not active in their intact form. They must physically reach the colon first. Nothing about the first eight hours indicates whether the dose will work.

8 to 12 hours: onset

The EMA monograph gives onset as 8 to 12 hours, the lag being transit time plus bacterial metabolism, and older sources cite 6 to 8 hours. Variability between individuals tracks colonic microbiota, because bacteria and not human enzymes generate the active compound, so someone recently treated with broad-spectrum antibiotics may respond weakly. In practice a 10 p.m. dose lands between 6 a.m. and 10 a.m.

Day 2 to day 7: the sanctioned window

The monographs endorse 2 to 3 doses total in this period. Producing the effect every day is not a sign the product is working better.

Beyond day 7: where the recommendation actually comes from

The one-week ceiling is not derived from a trial that found harm on day 8. It rests on three older and softer observations. First, chronic anthranoid use is associated with hypokalemia, and potassium depletion both worsens constipation and raises cardiac risk, so the drug becomes self-perpetuating. Second, prolonged use produces pseudomelanosis coli, documented after as little as a few months of use and in one mono-preparation case after 4 years. Third, the genotoxicity data package for hydroxyanthracene derivatives is incomplete, which is precisely the data FDA asked for in 1998 and never received. The limit is a boundary drawn around an evidence gap, not around a demonstrated threshold.

2 to 4 weeks of continuous use: functional changes

Tolerance, escalating doses and the pattern often labeled laxative dependence appear here, along with clinically detectable electrolyte problems in the people who develop them.

Months, then reversal

Pseudomelanosis coli can appear within a few months of regular use. It is lipofuscin accumulated in macrophages in the lamina propria, not melanin, and it is asymptomatic. Pigmentation regresses over several months to about a year after stopping. Bowel function recovery after chronic use is slower and often needs a structured taper onto an osmotic agent.

Benefits of Taking Cascara Sagrada

Reliable relief of occasional constipation

The effect is consistent enough that cascara was a monograph drug for decades before 2002. Two older controlled trials sit behind the European well-established use designation. Stern (1966) ran a randomized double-blind study in 25 institutionalized elderly patients aged 59 to 86, median 70.7 years, using a tablet containing 162 mg prune concentrate plus 162 mg cascarin, and reported that 22 of 25 patients, 88 percent, met all four prespecified criteria. Mauracher and colleagues (1976) ran a randomized double-blind crossover trial in 47 patients with chronic constipation, most over 70, and found cascara equal in effect to glucofrangulin and to bisacodyl in moderate cases.

Predictable timing and low systemic exposure

The 8 to 12 hour onset is consistent enough to plan around, and the pharmacology is largely local. Vyth and colleagues (1979) recovered rhein and traces of chrysophanol in urine after doses of 60 to 100 mg of cascara extract.

No demonstrated colorectal cancer signal

The largest direct test of the long-standing concern is Nusko G, Schneider B, Schneider I, Wittekind C, Hahn EG, Gut, 2000 May;46(5):651-655. This prospective case-control study at the University of Erlangen enrolled 202 patients with newly diagnosed colorectal carcinoma, 114 with adenomatous polyps, and 238 colonoscopy controls with no neoplasia. Unadjusted odds ratios for anthranoid use were 1.0 (95% CI 0.5 to 1.9) for adenoma and 1.0 (95% CI 0.6 to 1.8) for carcinoma. After adjustment for age, sex and blood in the stool, the odds ratios were 0.84 (95% CI 0.4 to 1.7) and 0.93 (95% CI 0.5 to 1.7). Macroscopic and high-grade microscopic melanosis coli were likewise not significant risk factors.

Potential Negatives & Side Effects

Common

• Abdominal cramping and griping, the most frequently reported effect, dose-dependent and worse with poorly aged bark

• Loose or watery stools when the dose exceeds what the individual needs

• Nausea, and harmless yellow-brown or reddish discoloration of urine from anthraquinone metabolites

With repeated or prolonged use

• Hypokalemia. Stimulant laxatives increase potassium losses in stool, and low potassium causes muscle weakness and, in the wrong context, cardiac arrhythmia. Sodium and magnesium losses and dehydration accompany it.

• Pseudomelanosis coli. Prevalence in colonoscopy series is low: 0.8 to 1.1 percent in the Wittoesch series from Rochester, Minnesota, and 1.8 percent in a multicenter Chinese analysis of 342,922 colonoscopies, with higher rates in men over 60.

• Tolerance and escalating dose requirement, and in severe chronic abuse, the protein-losing enteropathy and secondary hyperaldosteronism described in the laxative abuse literature

Uncommon and serious

• Hepatotoxicity. Nadir A, Reddy D, Van Thiel DH, American Journal of Gastroenterology, 2000 Dec;95(12):3634-3637, reported a 48-year-old man who developed jaundice within 3 days of starting cascara sagrada, with bilirubin 11.8 mg/dL, ALT 999 U/L and alkaline phosphatase 309 U/L, progressing to ascites and portal hypertension, recovering over 3 months after stopping. Jacobsen C, Semb S, Kromann-Andersen H, Ugeskrift for Laeger, 2009 Nov 9;171(46):3367-3369, reported a 49-year-old woman with jaundice 4 weeks into daily use, bilirubin rising from 8.4 to 24.6 mg/dL, ALT 944 U/L, ascites, and recovery over 4 months. The Spanish registry reported by García-Cortés and colleagues in 2008 included two cascara cases, one of them with onset at 2 months, bilirubin 7.1 mg/dL and ALT at 56 times the upper limit of normal, resolving in 3 months.

• Hypersensitivity reactions

Frequency context

Hepatotoxicity from cascara is rare, a handful of published cases against a very large historical exposure base. The pattern is idiosyncratic rather than dose-dependent, so it is not avoidable by dose reduction, and at least one case recurred on rechallenge.

Deficiency Symptoms

Cascara sagrada is not an essential nutrient, so there is no deficiency state. No recommended intake exists, no blood or tissue marker of cascara status exists, and no physiological process in the human body requires cascarosides at any level. A person who never consumes cascara sagrada has no cascara-related risk of any kind.

What cascara sagrada addresses

Cascara treats constipation, a presenting complaint with many causes, not a shortage of anything in the bark. Constipation is most commonly driven by low dietary fiber, inadequate fluid, inactivity, and medication effects from opioids, anticholinergics, calcium channel blockers, iron and some antidepressants. It is also caused by hypothyroidism, hypercalcemia, hypokalemia, diabetic autonomic neuropathy, pelvic floor dyssynergia, and mechanical obstruction including colorectal cancer. A stimulant laxative corrects none of them, and makes several harder to detect.

Bottom line

Nobody develops a problem from not taking cascara sagrada. The question is never whether you are getting enough, but whether the constipation has been explained, and whether fiber, fluid, activity and an osmotic agent have been tried first.

Toxicity Symptoms

At high intake

• Severe abdominal cramping, colic and profuse watery diarrhea

• Vomiting, the hallmark effect of insufficiently aged bark, caused by free anthrones

• Dehydration, with dizziness, reduced urine output and postural symptoms

• Hypokalemia, causing muscle weakness, fatigue and, when severe, cardiac arrhythmia

• Metabolic alkalosis and secondary hyperaldosteronism, described after prolonged heavy use in the laxative abuse literature

• Hematuria and albuminuria, described in the monographs as a consequence of long-term use

Signs to reduce or stop

• More than one loose stool per dose, which means the dose is too high

• Cramping that persists between doses

• Muscle weakness, palpitations or an irregular pulse, all of which point at potassium

• Yellowing of the skin or eyes, dark urine with pale stools, or right upper quadrant pain, any of which warrants stopping immediately and getting liver enzymes checked

• Rash, itching, or facial or throat swelling

• Needing a higher dose than last week for the same result

General note

Fatal poisoning from cascara is not a documented hazard in the standard references, and acute risk is dominated by fluid and electrolyte loss rather than direct organ damage. The realistic hazards are dehydration, potassium depletion in people whose cardiac or renal status makes that dangerous, and the rare idiosyncratic liver injury no dose adjustment prevents. The risk of one correctly dosed night differs enormously from six weeks of nightly use, and almost all reported harm sits in the second category.

How Cascara Sagrada Works

Step 1: the compound that is swallowed is not the compound that acts

Cascarosides A, B, C and D are glycosides whose C-glycosidic bonds resist hydrolysis by human digestive enzymes and stomach acid, and the molecules are too polar to be absorbed efficiently in the small intestine. They arrive in the colon intact.

Step 2: colonic bacteria do the activation

Bacterial beta-glucosidases cleave the O-glycosidic sugar and bacterial reductases convert the released aglycones into anthrones, the pharmacologically active species. Cascara is a prodrug in the strict sense, and its effect depends on an individual’s gut flora.

Step 3: two parallel effects on the colon

The anthrones act on colonic epithelium and on the enteric nervous system. The motility effect increases propulsive peristalsis, shortening the time available for water reabsorption. The secretory effect shifts the epithelium toward net secretion of water and electrolytes, through inhibition of Na+/K+-ATPase and stimulation of chloride secretion, with prostaglandin and nitric oxide mediation described experimentally.

Step 4: limited systemic exposure

Some aglycone material is absorbed, conjugated in the liver as glucuronides and sulfates, and excreted in urine and bile. Measured plasma concentrations are small: rhein at 6 to 28 ng/mL, aloe-emodin under 2 ng/mL and only intermittently detectable.

Why the aging requirement exists, mechanistically

Fresh bark carries high concentrations of free anthrones and reduced anthranols, and those are the compounds responsible for the vomiting and violent cramping caused by fresh cascara. Over one to three years of storage, or under controlled heat treatment or aeration, they oxidize to the corresponding anthraquinones and glycosidic forms, which are far gentler. The USP one-year collection requirement is a chemical specification written in the language of time.

Synergistic Supplements

Magnesium and soluble fiber

Magnesium hydroxide and magnesium citrate work osmotically rather than as stimulants, and an osmotic agent is a better first-line choice than cascara for most people. Psyllium and partially hydrolyzed guar gum address the underlying problem rather than forcing an outcome. Both should be taken with adequate fluid and spaced in time from cascara, because bulk fiber and a stimulant together increase cramping.

Potassium monitoring

A safety measure rather than a pairing. Anyone using an anthranoid alongside a diuretic or digoxin should have serum potassium checked rather than guessed at.

Adequate water, and ginger for tolerability

The laxative effect depends on drawing fluid into the lumen, and taking cascara while underhydrated produces the cramping without the comfortable outcome. Ginger is used traditionally to reduce anthranoid griping. That pairing rests on tradition rather than trials, and it addresses a side effect rather than improving the laxative action.

What is not synergy

Combining cascara with senna, aloe latex, rhubarb root or buckthorn is additive dosing of one mechanism dressed up as a formula. Four anthranoids at 25 percent of a dose each is one full dose, split across four label lines so none looks large.

Interactions & What NOT to Take

Cardiac glycosides, including digoxin

The most clinically important interaction. Potassium loss from stimulant laxatives increases myocardial sensitivity to digoxin and raises the risk of arrhythmia at ordinary serum digoxin concentrations. Every monograph on this bark carries this warning.

Loop and thiazide diuretics

Additive potassium and magnesium loss. Furosemide, hydrochlorothiazide and chlorthalidone compound the effect.

Systemic corticosteroids, licorice root and antiarrhythmics

Corticosteroids add potassium loss through a separate mechanism. Glycyrrhizin from licorice promotes potassium loss and sodium retention, and stacked with an anthranoid it is a recognized route to clinically significant hypokalemia. Quinidine and other antiarrhythmics matter because QT interval and potassium status interact.

Oral medications generally

Accelerated colonic transit reduces the absorption window for other oral drugs. Space cascara from oral contraceptives, thyroid hormone, anticonvulsants, anticoagulants and any narrow-therapeutic-index medication by at least 1 to 2 hours, and preferably longer.

Other stimulant laxatives

Senna, bisacodyl, sodium picosulfate, aloe latex, rhubarb root, buckthorn bark. Do not stack.

Hepatotoxic medications

Given the case reports, avoid combining cascara with agents already carrying meaningful hepatotoxicity risk, and stop it if liver enzymes are elevated for any reason.

What to tell a clinician

Name cascara sagrada specifically before any surgery or colonoscopy, and at any visit where potassium, liver enzymes or digoxin levels come up. It goes unmentioned because people class it as a tea rather than a drug.

Quality, Testing & Adulteration

Cascara has clear specifications and weak routine enforcement in the US supplement channel.

The aging requirement is the first thing to verify

The USP note reads: collect cascara sagrada not less than one year prior to use. Pacific Northwest practice ages dried bark one to three years. Bark that is fresh, or dried and shipped inside a few months without heat treatment or aeration, contains free anthrones and causes vomiting and violent cramping. A consumer cannot detect this except by asking the manufacturer for the harvest date and aging protocol, and most cannot answer.

Assay specifications worth requesting

• USP dried bark: not less than 7.0 percent total hydroxyanthracene derivatives calculated as cascaroside A on the dried basis, with not less than 60 percent of that total being cascarosides

• Ph. Eur. standardized dry extract, monograph 01/2008:1844: 8.0 to 25.0 percent m/m hydroxyanthracene glycosides as cascaroside A, assayed at 90 to 110 percent of the nominal declared value, with a minimum of 60 percent of the glycosides being cascarosides

• Loss on drying: USP allows not more than 12.0 percent weight loss after 5 hours at 105 degrees C

Why the cascaroside percentage is the number that matters

Total anthracene content is easy to hit and tells you little. A sample dominated by free anthraquinones and dimers can meet a total-anthracene figure while carrying almost no laxative activity. The 60 percent cascaroside floor exists to prevent that, and very few US certificates of analysis report the fraction separately.

Species substitution

• Frangula alnus Mill., alder buckthorn, also called Rhamnus frangula L. Its bark is a legitimate anthranoid laxative in Europe, but it is standardized to glucofrangulin A rather than cascaroside A, and the two assays are not interchangeable. A cascara product substituted with frangula bark can pass a generic total-anthraquinone test and fail a cascaroside-specific one.

• Rhamnus cathartica L., common buckthorn. Naturalized and invasive across North America, so it is cheap and abundant, and its bark and berries are harsher.

• Other Frangula and Rhamnus species in the trade, several morphologically similar once the bark is cut or powdered.

How identity should actually be established

Powdered bark cannot be identified visually with confidence. Serious identity work is orthogonal: HPTLC fingerprinting against an authenticated reference, HPLC quantification of cascaroside A specifically, and DNA barcoding of the raw material. Microscopy is diagnostic too, and the USP monograph names the markers, including stone cells in tangentially elongated groups of 20 to 50 cells, phloem rays 1 to 4 cells wide and 15 to 25 cells deep, starch grains up to 8 micrometers, and calcium oxalate prisms and rosettes of 6 to 20 micrometers.

Sourcing and contaminants

The bark is wild-harvested, and peeling it from a standing trunk kills the tree unless the harvest is done by coppicing. Cascara populations in parts of the Pacific Northwest have been reduced by decades of overharvest, and coppice-managed sourcing is rarely documented on a label. Wild-stand bark should carry heavy metal, pesticide residue and microbial testing.

Special Considerations

Pregnancy and breastfeeding

Contraindicated in both. The EMA monograph excludes pregnancy, with osmotic agents and fiber as the accepted approaches. In breastfeeding the pharmacokinetic picture is reassuring rather than alarming: small amounts of rhein appear in human milk, and no laxative effect in breastfed infants has been reported. That contraindication reflects absence of adequate data rather than evidence of harm.

Children under 12

Contraindicated outright. No pediatric posology exists.

Older adults

Higher baseline risk of hypokalemia, dehydration and drug interactions. Both supporting trials ran in elderly populations, so the efficacy data fits this group, but the safety margin is narrower.

Surgery and liver disease

Stop well before any scheduled procedure. Avoid entirely in liver disease: the published cases involve people with no prior liver disease, and there is no reason to add an idiosyncratic hepatotoxin to a compromised liver.

Regulatory status by jurisdiction

• United States: not GRASE as an OTC laxative drug since November 5, 2002, listed at 21 CFR 310.545, restated in FDA’s final administrative order for OTC laxative drug products, OTC000032 (M007), issued May 2, 2023. Legal as a dietary supplement.

• European Union: a regulated herbal medicinal product under the EU herbal monograph Rhamni purshianae cortex, Revision 1 adopted 6 May 2020, for short-term relief of occasional constipation.

• European Union food law: Commission Regulation (EU) 2021/468 of 18 March 2021 amended Annex III of Regulation (EC) No 1925/2006, prohibiting aloe-emodin, emodin, danthron and preparations from the leaf of Aloe species containing hydroxyanthracene derivatives, and placing bark preparations of Rhamnus frangula L. and Rhamnus purshiana DC. under Union scrutiny. On 13 November 2024 the General Court, in Aloe Vera of Europe BV v Commission and related actions (T-189/21, T-271/21, T-274/21, T-302/21), annulled those entries other than danthron, holding that the Commission had exceeded its powers under that legal basis. The EU position is therefore unsettled, and the underlying EFSA safety concern has not been withdrawn.

The EFSA assessment that drove the EU action

The EFSA panel opinion adopted 22 November 2017 and published in the EFSA Journal 2018;16(1):5090 concluded that aloe-emodin, emodin and danthron are genotoxic and that no safe daily intake could be established. Underlying it were the National Toxicology Program rodent studies on emodin, which found 3 Zymbal’s gland carcinomas in female rats at 2,500 ppm and low incidences of renal tubule adenoma and carcinoma in exposed male mice, classified by NTP as equivocal evidence in female rats and male mice and no evidence in male rats and female mice. The signal is weak and the human data set is thin, which is why regulators reach for precautionary limits.

Research Status & Evidence Quality

Strong Evidence For

• Laxative effect. The mechanism is understood at the level of bacterial activation and colonic secretion, and the effect is reproducible. Nobody disputes it, FDA included, whose 2002 action concerned missing safety data rather than absence of effect.

• Onset timing of 8 to 12 hours.

• Chemistry and analytical identity. Cascarosides A through D are fully characterized, with pharmacopoeial assays in both USP and Ph. Eur.

Moderate Evidence For

• Short-term efficacy in constipation in older adults, resting on two small randomized double-blind trials: Stern (1966), n=25, and Mauracher and colleagues (1976), n=47 crossover. Both are small, both are at least 50 years old, and one used a combination product containing prune concentrate, which complicates attribution.

• Absence of colorectal neoplasia risk, on the Nusko 2000 odds ratios of 0.93 and 0.84 cited above. It is a single well-conducted case-control study, and it addresses anthranoids as a class rather than cascara specifically.

• Pseudomelanosis coli as a consequence of chronic use, and its reversal over several months to a year after discontinuation.

Emerging / Preliminary Evidence For

• Hepatotoxicity as a causal association. A handful of published case reports with consistent features, positive dechallenge and at least one positive rechallenge. Enough for a probable causal signal, not enough to estimate incidence.

• Genotoxicity at the whole-preparation level. In vitro mutagenicity is documented for emodin in Salmonella typhimurium TA100 with S9 activation and for aloe-emodin in TA1537, TA98, TA1538 and TA97, with 2-hydroxyemodin the proximate genotoxin. In vivo confirmation is weak, and Heidemann and colleagues (1996) found no indication of mutagenic activity for aloe-emodin in vivo.

Research Limitations

• No modern randomized controlled trial of a standardized cascara preparation has been published. The efficacy evidence is 50 and 60 years old.

• No trial has compared cascara head-to-head with polyethylene glycol, the current first-line agent.

• No long-term safety study exists. The one-week limit is a precaution extrapolated from class data, not a figure derived from a study that looked at week 2.

• The mutagenicity, genotoxicity and carcinogenicity data FDA requested in 1998 was never generated, and still has not been, 28 years later.

• A trial of 425 mg of dried bark is a trial of an unknown anthracene dose unless the bark was assayed, and most published work predates the standardized extract monograph. Almost all mechanistic and toxicological work uses isolated anthranoids rather than whole bark, so the toxicology of the compounds and the risk profile of the preparation are related but not identical.

Summary & Key Takeaways

Cascara sagrada works. That is the easiest thing to say about it and the hardest thing to build a case on, because working and being adequately studied are separate questions, and this bark has only the first. It has a pharmacopoeial identity, a real mechanism, a predictable 8 to 12 hour onset, and two small randomized trials from 1966 and 1976 behind a European well-established use designation. It also carries FDA’s 2002 determination that it is not generally recognized as safe and effective as an OTC laxative, issued because the safety data requested in 1998 was never supplied. Both facts are true at once, and the shelf location changed while neither of them did.

Bottom Line

For an adult with occasional constipation who has already tried fiber, fluid, activity and an osmotic agent, a short course at 10 to 30 mg hydroxyanthracene derivatives as cascaroside A, once at night, on 2 or 3 nights within a single week, is defensible. Outside that description the case weakens quickly. Anyone reaching for it daily, or in week 3, is treating a symptom whose cause has not been established with a drug whose long-term safety has not been studied.

Key Safety Points

• Hard ceiling of 1 week. Commission E is commonly cited as allowing 8 to 10 consecutive days. Neither figure is a suggestion.

• Contraindicated in pregnancy, in breastfeeding, in children under 12, in intestinal obstruction, in inflammatory bowel disease, and in undiagnosed abdominal pain.

• The potassium interaction with digoxin, diuretics, corticosteroids and licorice is the interaction most likely to cause real harm.

• Jaundice, dark urine or right upper quadrant pain means stop immediately and get liver enzymes checked. Documented cases include bilirubin of 24.6 mg/dL and ALT of 999 U/L.

• Verify the bark was aged at least 1 year. The USP requirement exists because unaged bark causes vomiting.

• Ask for the cascaroside percentage rather than total anthraquinones alone. USP requires at least 60 percent of hydroxyanthracene derivatives to be cascarosides.

Special Note

The name on the label is probably still Rhamnus purshiana. The accepted botanical name is Frangula purshiana (DC.) A.Gray ex J.G.Cooper, and the genus was separated on real characters, confirmed by molecular work: Frangula has five petals where Rhamnus usually has four, buds without scales, branches without spines, and undivided styles. Plastid and nuclear sequence analyses by Richardson and colleagues in 2000 and by Bolmgren and Oxelman in 2004 supported the split. The practical consequence is worth knowing. When you compare a certificate of analysis, a pharmacopoeial monograph and a product label, three different names may be describing the same tree, and two different trees may be hiding behind one name.