Rhubarb Plant
Botanical Description & Habitat
Rheum palmatum
Common names
Chinese rhubarb
Turkey rhubarb
Habitat
Native to China and Tibet, grown elsewhere for ornamental purposes.
Description
The conical rootstock, which is fleshy and yellow inside, produces large, cordate, or almost orbicular, 7-lobed leaves on thick petioles from 12 to 18 inches long. A hollow flower stem, 5 ot 10 feet high, also grows from the rootstock and is topped by a leafy panicle of green or white flowers.
Medicinal parts
Rootstock
Historical Properties & Uses
Rhubarb has a history as an ingredient in many laxative preparations. It is generally considered a mild laxative producing a soft stool 6-10 hours after ingestion, but should not be used by itself when the colon is totally evacuated, because the presence of astringent tannins may produce constipation. On very rare occasions, sensitive persons may experience mild colicky pains.
Rhubarb is important because its anthraquinones differ somewhat from those of cascara sagrada or buckthorn. Only some of rhubarb's anthraquinones reach the large intestine intact, while many are resorbed in the small intestine and later released into the large intestine. The timing of the activity of rhubarb thus differs somewhat from cascara. As with other anthraquinones, those of rhubarb do not become active until, through fermentation by bacteria in the large intestine and intestinal wall, they undergo moderate chemical change. Only then do they stimulate secretion of mucus through the wall of the large intestine, whereby the consistency of the intestinal contents is decreased. They also reflexively stimulate the musculature of the wall lining, whereby peristalsis and bowel emptying are increased.
Rhubarb is especially well suited for children since it is very mild in action. For chronic constipation, it may be used year-round, but should only be given when necessary, since prolonged use may lead to potassium deficiency and chronic constipation. In the absence of constipation, but in case of mild diarrhea, small amounts of rhubarb can be antidiarreic due to the tannins. Rhubarb is generally used in blends with other laxatives such as cascara, butternut and buckthorn.
Rhubarb has also been found beneficial in numerous other problems; it relieves liver, spleen, and gallbladder problems, especially gallstones, jaundice, hemorrhoids, and upper digestive tract bleeding. It also has anti-bacterial, anti-inflammatory and hypotensive actions.
This herb has approval status by the German Commission E for constipation.
References:
Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.
Method of Action
Rhubarb contains two major classes of active components: anthraquinones and tannins (catechin and gallic acid). The anthraquinones are cathartic; the tannins are astringent.
Rhubarb is a reliable laxative when used properly
The proper use of rhubarb is as a single large dose. Because it is mild, a large dose will not produce unwarranted griping. Should repeated treatments become necessary, a change to cascara is recommended to avoid habituation. Rhubarb produces a soft stool 6-10 hours after ingestion, but should not be used by itself when the colon is totally evacuated, because the presence of astringent tannins may produce constipation.
Rhubarb can remedy upper digestive tract bleeding
Rhubarb's ability to stop bleeding has been known for over 1,700 years. In a recent 3-year study, a total of 400 patients suffering from upper digestive tract bleeding were treated with rhubarb powder or tablets in doses of 3 grams 2-4 times per day until occult blood ceased to appear in the stool. Patients with hemorrhage due to cirrhosis of the liver or rupture of the esophagus were excluded from the study. Of the 400 cases, only 11 were failures: 97% showed absence of occult blood in an average time of 1.5 days (shortest time was 5 hours, longest time was 14.5 days).
The average therapeutic amount of rhubarb was 15 g. Over 95% of the patients reported abdominal pain after taking the rhubarb, but when bowel movement occurred, the pain lessened or disappeared.
Compared to other orthodox treatments, rhubarb stopped the bleeding very rapidly, therein decreasing blood loss, and reducing the need for coagulant drugs, caused rapid disappearance of absorption fever, increased appetite, corrected anemia. The herb was easy to obtain and use, and was reliable. Its mode of action is not yet clear.
Rhubarb has antibiotic effects
The respiration of Staphylococcus aureus in ordinary broth is strongly inhibited by emodin, aloe emodin, and rhein of minimal growth-inhibitory concentration. The percentages of inhibition range from 42-83%.
Drug Interactions & Precautions
Known Interactions
Rhubarb will potentiate the effects of other laxatives, cathartics, and purgatives.
Rhubarb, due to its cathartic activity, may potentiate anticoagulant therapy by reducing absorption of vitamin K from the gut. It may also inhibit absorption of dextrose from the intestines.
This cathartic increases the intestinal transit time. It may therefore inhibit the absorption of digitalis glycosides and decrease their cardiac action. But cathartic-induced hypokalemia increases toxicity and potency of absorbed digitalis. Cathartic-induced hypokalemia potentiates muscle relaxants.
The German Commission E also notes the possibility for chronic use of rhubarb, via depletion of potassium resources, to potentiate cardiac glycosides and interact with antiarrhythmia drugs.
In additions to the specific interactions listed, the cathartic action of rhubarb tends to hasten the passage of all oral medications through the gut and thereby inhibit their action.
Possible Interactions
Laxative-induced diarrhea may result in decreased absorption of isoniazid and thereby inhibit their action.
The same is true with sulfisoxazole, but it appears to be a clinically unimportant interaction effect.
Comments
Laxative-induced increased speed of intestinal emptying may result in decreased absorption of vitamin K and/or anticoagulants.
References:
Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.
Safety Factors & Toxicity
Rhubarb contains astringent tannins which may produce rebound constipation following bowel evacuation. Therefore, it is normally not included among the most-recommended laxatives. Research indicates, however, this is not the case if the plant is used properly.
Rhubarb leaf is highly toxic and should be avoided completely.
Rhubarb root has approval status by the German Commission E.
The German Commission E recommends a limited duration for the use of this herb of not over 2 weeks without medical advice.
References:
Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.
Preparation & Administration
This herb has approval status by the German Commission E.
Recommended daily dosages in Germany are as follows:
20 - 30 mg calculated as rhein.
The German Commission E recommends a limited duration for the use of this herb of not over 2 weeks without medical advice.
References:
Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.
References
Am Hospital Formulary Service. Am Soc of Hosp Pharm. Wash, D.C.
Azarnoff, D.L. & A. Hurwitz. 1970. Drug interactions. Pharmacol Physicians, 4(2). pp. 1-7.
Beckman, H. 1967. Dilemmas in drug therapy. Saunders, Philadelphia.
Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.
Bressler, R., M.D. Bogdonoff & G.J. Subak-Sharpe. 1981. The Physicians Drug Manual. Doubleday & Co, Inc. Garden City, NY. 1213 pp.
Chen, C.H., T.T. Li, H.L. Su & C.I. Wang. Chinese rhubarb. Vii. Mechanism of antibiotic action of anthraquinone derivatives. Effects on the respiration of staphylococcus aureus. Sheng Wu Hua Hsueh Yu Sheng Wu Wu Li-sueh Pao 3(4), 426-433, 1963.
Chirikdjian, Kopp & Beran. Ueber die laxative wirkung eines neuen anthraquinonglykosides aus rhadix rhei. Plant Medica, 48, 34-37, 1983.
Goodman, L.S. & A. Gilman. 1975. Pharm Basis of Thera. MacMillan, NY.
Hansten, P.D. 1979. Drug Interactions, 4th ed. Lea & Febiger, Phila.
Hansten, P.D. 1969. Oral anticoagulant drug interactions. Hospital Form. Management, 4(1). pp. 20-22.
Interactions of drugs. Med Let Drugs Ther, 12(11). pp. 93-96.
Jiao., et. al. Resume of 400 cases of acute upper digestive tract bleeding treated with rhubarb alone. Pharmacology, 20 (Suppl. 1), 128-130, 1980.
Kastrup, E.K., ed. 1981. Drug Facts and Comparisons, 1982 edition. Facts and Comparisions Division, J.P. Lippincott Co, Phila(St. Louis).
List, P. & L. Hoerhammer. 1969-1976. Hagers Hanbuch der Pharmazeutischen Praxis, vols. 2-5. Springer-Verlag, Berlin.
Lust, J. B. 1980. The Herb Book. Benedict, Lust Publ. California.
Martin, E.W. 1978. Drug Interactions Index, 1978/79. J.B. Lippincott Company, Philadelphia.
Mattila, M.J., et.al. 1974. Effect of sodium sulphate and castor oil on drug absorbtion from the human intestine. Ann of Clin Rsrch, 6.
Mowrey, Daniel B., Ph.D. Exper. Psych., Brigham Young University. Director of Nebo Institute of Herbal Sciences. Director of Behavior Change Agent Training Institute. Director of Research, Nova Corp.
Prescott, L.F. Dec. 6, 1969. Pharmacokinetic drug interactions. Lancet, 2. pp. 1239-1243.
Su, H.L. & C.H. Chen. Chinese rhubarb. II. Paper chromatography of anthraquinone derivatives. Yao Hsueh Hsue Pao, 10(12). 725-730, 1963.
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