Herb-Drug Interactions: Rhubarb

2011

Rheum officinale Baill., Rheum palmatum L. (Polygonaceae)

Synonym(s) and related species

Chinese rhubarb.

Rheum tanguticum Maxim.

Note that Indian rhubarb (Himalayan rhubarb) consists of the dried root of Rheum emodi Wall, or some other related species of Rheum.

Note also that the root of Rheum rhaponticum Willd (English rhubarb, Garden rhubarb) sometimes occurs as an adulterant in rhubarb and pharmacopoeias specify a test for its absence.

Pharmacopoeias

Compound Rhubarb Tincture (British Pharmacopoeia 2009); Rhubarb (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4).

Constituents

Anthraquinone glycosides are major components of rhubarb. It contains chrysophanol, emodin, rhein, aloe-emodin, physcion and sennosides A to E. Various tannins, stilbene glycosides, resins, starch and trace amounts of volatile oil are also present.

Indian rhubarb contains similar anthraquinones, but English rhubarb contains only chrysophanol and some of its glycosides.

Use and indications

Rhubarb rhizome and root is used as a laxative, but at low doses it is also used to treat diarrhoea, because of the tannin content. It is also used as a flavouring in food.

Pharmacokinetics

For information on the pharmacokinetics of an anthraquinone glycoside present in rhubarb, see under aloes.

Interactions overview

A case report describes raised digoxin levels and toxicity in a patient taking a Chinese herbal laxative containing rhubarb (daio), see Liquorice + Digitalis glycosides for further details.

No further interactions with rhubarb found; however, rhubarb (by virtue of its anthraquinone content) is expected to share some of the interactions of a number of other anthraquinone-containing laxatives, such as aloes and senna9. Of particular relevance are the interactions with corticosteroids and potassium-depleting diuretics.