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What is Crampbark?

Viburnum opulus is a large bush that often is grown ornamentally for its attractive white flowers. It is native to northern Asia and Europe. The American variety of V. opulus (also known as V. trilobatum) has edible red berries, while the European variety bears bitter fruit. The trunk and root bark are the commonly used drug products.

Scientific Name(s)

Viburnum opulus, V. opulus var. americanum

Common Name(s)

Cramp bark also is known as guelder rose, snowball, squaw bush, cranberry tree, highbush cranberry, and pimbina.

What is it used for?

Traditional/Ethnobotanical uses

The American variety was used by the Iroquois for prolapsed uterus after childbirth, and other tribes recognized its use as a diuretic. The Eclectic medical movement in the 19th century adopted cramp bark for dysmenorrhea and to prevent miscarriage. It was believed to be a stronger antispasmodic than the related Viburnum species V. prunifolium (black haw). The bark was made official in the U.S. Pharmacopeia in 1894 and was included in the National Formulary in 1916. Widespread adulteration by mountain maple (Acer spicatum) and other Viburnum species led to confusion about the correct source plant. A later review surveyed the botanical, chemical, and pharmacological differences between black haw and cramp bark.

Uterine relaxant

Cramp bark has been used for painful menstruation and to prevent miscarriage. Animal studies show that cramp bark relaxes uterine tissues. However, no clinical studies examining efficacy in humans have been performed.

What is the recommended dosage?

3 to 4 g/day.


Contraindications have not yet been identified.


Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.


None well documented.

Side Effects

No studies have been performed.


There are no studies of the toxicology of cramp bark.


1. Cramp Bark. Review of Natural Products. factsandcomparisons4.0 [online]. 2006. Available from Wolters Kluwer Health, Inc. Accessed April 23, 2007.

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