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Since May 10th 2008

Initial R

Rauvolfia serpentina
Rheum officinale
Rhamnus frangula
Rhamnus purshiana
Rehmannia glutinosa



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Untitled Document Rheum officinale Baill., or R. palmatum L. (Polygonaceae)

Rheum species are perennial herbs resembling the common garden rhubarb except for their lower growth and shape of their leaf blades; the underground portion consists of a strong vertical rhizome with fleshy, spreading roots; the portion above ground consists of a number of long petioled leaves that arise from the rhizome in the spring, and flower shoots bearing elongated leafy panicles that are crowded with greenish white, white, to dark purple flowers; the lamina is cordate to somewhat orbicular, entire or coarsely dentate (Rheum officinale) or palmately lobed (R. palmatum). The fruit is an ovoid-oblong or orbicular achene bearing 3 broad membranous wings and the remains of the perianth at the base

Plant material used
rhizomes and roots

Chemical assays
Contains not less than 2.2% hydroxyanthracene derivatives calculated as rhein. Quantitative analysis of total hydroxyanthracene glycosides, calculated as rhein, performed by spectrophotometric analysis. High-performance liquid chromatography is also available for quantitative analysis. Thin-layer chromatography is employed for the qualitative analysis for the presence of emodin, physcione (emodin 3-methyl ether), chrysophanol (chrysophanic acid), rhein, and aloe-emodin)

Major chemical constituents
The major constituents are hydroxyanthracene derivatives (2–5%) including emodin, physcione, aloe-emodin, and chrysophanol glycosides, along with di-O, C-glucosides of the monomeric reduced forms (rheinosides A–D), and dimeric reduced forms (sennosides A–F). The level of the oxidized forms is maximal in the summer and almost nil in the winter (12). Until the 1950s, chrysophanol and other anthraquinones were considered to be the constituents producing the purgative action of rhubarb. Current evidence indicates that the major active principles are the dimeric sennosides A–F

Dosage forms
Dried plant material and preparations standardized to contain 10–30mg of hydroxyanthracene derivatives per dose. Package in well-closed, lightresistant containers.

Medicinal uses
Uses supported by clinical data
Short-term treatment of occasional constipation.

Uses described in pharmacopoeias and well established documents

Uses described in traditional medicine
To treat hypotension, increase peripheral vasodilation, and inhibit blood coagulation

Proven pharmacological activity
Animal studies

Human studies

The major symptoms of overdose are griping and severe diarrhoea with consequent losses of fluid and electrolytes. Treatment should be supportive with generous amounts of fluid. Electrolytes, particularly potassium, should be monitored, especially in children and the elderly.

As with other stimulant laxatives, products containing Rhizoma Rhei should not be administered to patients with intestinal obstruction and stenosis, atony, severe dehydration states with water and electrolyte depletion, or chronic constipation. Rhizoma Rhei should not be used in patients with inflammatory intestinal diseases, such as appendicitis, Crohn disease, ulcerative colitis, or irritable bowel syndrome, or in children under 10 years of age. Rhizoma Rhei should not be used during pregnancy or lactation except under medical supervision after respective benefits and risks have been considered. As with other stimulant laxatives, Rhizoma Rhei is contraindicated in patients with cramps, colic, haemorrhoids, nephritis, or any undiagnosed abdominal symptoms such as pain, nausea, or vomiting.

Products containing Rhizoma Rhei should be used only if no effect can be obtained through a change of diet or use of bulk-forming laxatives. Stimulant laxatives should not be used when abdominal pain, nausea, or vomiting are present. Rectal bleeding or failure to have a bowel movement after the use of a laxative may indicate a serious condition. Use of stimulant laxatives for longer than the recommended short-term application may increase intestinal sluggishness. The use of stimulant laxatives for more than 2 weeks requires medical supervision. Chronic use may lead to pseudomelanosis coli (harmless) and to an aggravation of constipation with dependence and possible need for increased dosages. Chronic abuse with diarrhoea and consequent fluid and electrolyte losses (mainly hypokalaemia) may cause albuminuria and haematuria, and it may result in cardiac and neuromuscular dysfunction, the latter particularly in case of concomitant use of cardiac glycosides (digoxin), diuretics, corticosteroids, or liquorice root (see below, Precautions)

Laxatives containing anthraquinone glycosides should not be used for periods longer than 1–2 weeks continually, owing to the danger of electrolyte imbalance.

Drug interactions
Decreased intestinal transit time may reduce absorption of orally administered drugs. Electrolyte imbalances such as increased loss of potassium may potentiate the effects of cardiotonic glycosides (digitalis, strophanthus). Existing hypokalaemia resulting from long-term laxative abuse can also potentiate the effects of antiarrhythmic drugs, such as quinidine, which affect potassium channels to change sinus rhythm. Simultaneous use with other drugs or herbs which induce hypokalaemia, such as thiazide diuretics, adrenocorticosteroids, or liquorice root, may exacerbate electrolyte imbalance.

Drug and laboratory test interactions
Anthranoid metabolites may not be detectable with standard methods. Thus results of measuring faecal excretion may not be reliable. Urinary excretion of certain anthranoid metabolites may discolour the urine, which is not clinically relevant but may cause false positive results for urinary urobilinogen and for estrogens when measured by the Kober procedure.

Carcinogenesis, mutagenesis, impairment of fertility
Data on the carcinogenicity of Rhizoma Rhei are not available. While chronic abuse of anthranoid-containing laxatives was hypothesized to play a role in colorectal cancer, no causal relationship between anthranoid laxative abuse and colorectal cancer has been demonstrated.

Pregnancy: teratogenic effects
The teratogenic effects of Rhizoma Rhei have not been evaluated.

Pregnancy: non-teratogenic effects
Products containing Rhizoma Rhei should not be used by pregnant women because they have a pronounced action on the large intestine and have not undergone sufficient toxicological investigation.

Nursing mothers
Anthranoid metabolites appear in breast milk. Rhizoma Rhei should not be used during lactation as there are insufficient data available to assess the potential for pharmacological effects in the breast-fed infant

Paediatric use
Use of Rhizoma Rhei for children under 10 years of age is contraindicated.

Adverse reactions
Single doses may cause cramp-like discomfort of the gastrointestinal tract, which may require a reduction of dosage. Overdoses can lead to colicky abdominal spasms and pain and the formation of thin, watery stools. Chronic abuse of anthraquinone stimulant laxatives can lead to hepatitis. Long-term laxative abuse may lead to electrolyte disturbances (hypokalaemia, hypocalcaemia), metabolic acidosis, malabsorption, weight loss, albuminuria, and haematuria. Weakness and orthostatic hypotension may be exacerbated in elderly patients when stimulant laxatives are repeatedly used. Secondary aldosteronism may occur due to renal tubular damage after aggravated use. Steatorrhoea and protein-losing gastroenteropathy with hypoalbuminaemia have also been reported in laxative abuse. Melanotic pigmentation of the colonic mucosa (pseudomelanosis coli) has been observed in individuals taking anthraquinone laxatives for extended time periods. The pigmentation is clinically harmless and usually reversible within 4–12 months after the drug has been discontinued. Conflicting data exist on other toxic effects such as intestinal-neuronal damage after long-term use.

The individually correct dosage is the smallest dosage necessary to maintain a soft stool. The average dose is 0.5–1.5 g of dried plant material or in decoction; preparations standardized to contain 10–30mg of hydroxyanthracene derivatives, usually taken at bedtime


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