Cramp bark

Cramp Bark (Viburnum opulus L.)

1. Identity, Botanical Description, and Natural Sources

Cramp bark is the common name applied to the dried bark of Viburnum opulus L., a deciduous shrub in the family Adoxaceae (historically also classified within Caprifoliaceae). It is a member of the Adoxaceae family, a group of plants often characterised by their small, white or cream-coloured flowers arranged in clusters. The accepted scientific name is Viburnum opulus L., and botanical synonyms and recognized varieties include Viburnum opulus var. edule, Viburnum opulus var. sargentii (Koehne) Takeda, Viburnum opulus var. opulus, and Viburnum opulus var. americanum (Miller) Ait.

The American Herbal Pharmacopoeia® (AHP) recognizes two varieties of this medicinal species: V. opulus var. americanum (American) and V. opulus var. opulus (Eurasian). The European variety is the most popular in Europe, while V. opulus var. americanum Aiton grows in North America and V. opulus var. sargentii (Koehne) Takeda is native to Korea, northern China, and Japan.

Common Names and Synonyms

Common names include American cranberry bush, common snowball, cramp bark, cranberry bush, cranberry tree, European cranberry bush, Gilaboru/Gilaburu (Turkish), guelder rose, high cranberry, highbush cranberry, pimbina, snowball bush, and squaw bush.

Botanical Description and Habitat

The plant is an upright shrub 1–3.5 m tall, with small white flowers that grow in clusters. The leaves are dark green, have 3–5 lobes, and are approximately 6 cm wide at the broadest part. The fruit are small berries that are red to black in colour. The bark of Viburnum opulus is green-brown on the outer surface, and green-yellow to red-brown on the inner surface. The bark has a strong characteristic odour and tastes somewhat bitter.

Viburnum opulus is a valuable decorative, medicinal, and food plant. This deciduous shrub is found in natural habitats in Europe, Russia, and some regions in North Africa and North Asia. Cramp bark typically thrives in damp woodlands, hedgerows, and along the edges of streams or rivers, and is commonly found in temperate regions across Europe, North America, and Asia.

Medicinal Part Used and Harvesting

The bark is harvested in spring and summer when the plant is flowering. It is removed in strips from the young shoots, ensuring enough remains for the plant's continued growth. Cramp bark is the dried bark of Viburnum opulus L. The bark is harvested from wild or cultivated trees and extracted using water, 70% ethanol, or glycerin-based solvents to produce liquid extracts, tinctures, or powders.

Relationship to Black Haw

Viburnum opulus is native to Northern America and Europe, where it grows in woodlands and thickets. It is related to Viburnum prunifolium (Black Haw) and they are often used interchangeably. Viburnum opulus contains hydroquinones, coumarins, and tannins, whereas Viburnum prunifolium's primary constituents include coumarins, biflavones, and phenolic acids. The constituents of cramp bark are very similar to those of its close relative black haw (Viburnum prunifolium), although cramp bark and black haw should not be considered interchangeable in the strict sense.

2. Traditional and Historical Use

Native American Traditions

Traditional use is predominately in Northern America and Canada, where cramp bark was used by Native Americans as an anti-abortive, to remedy uterine prolapse, and as a spasmolytic for cramping pains in all parts of the body. A decoction of the bark was also used as a social beverage, diuretic, eye-wash, and for conditions involving swollen glands.

The Meskwaki tribe of Wisconsin used cramp bark to treat menstrual cramps and other painful conditions such as arthritis and back pain, whilst the Penobscot people of Maine used the herb to counter swollen lymph glands and gout. The North American variety, Viburnum opulus var. americanum, has been used by the Ojibwe, Menominee, Potawatomi, Iroquois, and Cree, who used the bark in decoctions for cramping and muscle tension. The American variety was also used by the Iroquois for prolapsed uterus after childbirth.

European Herbal and Folk Medicine

The medicinal use of cramp bark stretches back centuries in European herbal tradition. The bark was widely known as a remedy for muscular cramps and spasms by the 16th century, when herbalists including John Gerard described its use for relieving 'gripings of the belly' and calming uterine complaints.

In Eastern European folk medicine, the shrub held a prominent position — in Russia and Ukraine, where it is known as kalyna, the plant was considered sacred and symbolic of feminine beauty, love, and the homeland. An infusion of the bark is used in Russian traditional medicine to treat scrofula in children, asphyxia, colds, and uterine, gastric and hemorrhoidal bleeding. The bark has been used to treat high blood pressure, heart trouble, tuberculosis, and shortness of breath.

The Eclectic Medical Movement (19th Century)

Cramp bark was used by Eclectic practitioners of the 19th century for all types of cramping. Indications included dysmenorrhoea, threatened miscarriage, skeletal muscle cramping, ovarian pain, angina, palpitations, spasm of the bladder, and infantile enuresis. It was used interchangeably with Viburnum prunifolium, but was considered more specific to the uterus in its action and a more potent antispasmodic.

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. In 1952, the bark was also included in the State Pharmacopoeia of the USSR.

Cramp bark is included in the British Herbal Pharmacopoeia and is used by herbalists in the United Kingdom for miscarriage prevention. It is thought that at least four active substances, including scopoletin and aesculetin, which have been identified, have uterine spasmolytic activity.

Turkish Folk Medicine (Gilaburu)

In Turkey, the fermented fruit juice of European cranberrybush is known as gilaburu; in the middle Anatolian region, this traditional drink is considered useful for kidney disorders, menstrual and stomach cramps, hypertension, asthma, digestion problems, and the common cold. In Turkish folk medicine, the juice obtained by squeezing the fruits of V. opulus is taken orally to pass kidney stones. In inner Anatolia, a traditional drink named gilaburu has been prepared from the fruits of V. opulus.

3. Phytochemistry: Key Constituents and Active Compounds

Health benefits of V. opulus result from the presence of bioactive components such as phenolic compounds, vitamin C, carotenoids, iridoids, and essential oils, among others. The bark specifically is the primary medicinal part, and its chemical profile differs from the fruit. The bark of Viburnum opulus contains salicylates (e.g., salicin), coumarins (scopoletin and scopaline), tannins and phenolic acids (including caffeic, p-coumaric, ferulic, gallic, ellagic, and syringic acid derivatives), sesquiterpenes (viopudial and viburtinal), a resin glycoside (viburnin), valeric acid, proanthocyanidins (flavonols), and hydroquinone glycosides (arbutin).

Principal Antispasmodic Constituents

• Scopoletin: A coumarin that is the major constituent responsible for antispasmodic action. Evidence for its antispasmodic effects derives primarily from in vitro studies demonstrating calcium channel antagonism by scopoletin. Cramp bark contains the antispasmodic compounds scopoletin and viopudial, which relax smooth and skeletal muscle tissue by inhibiting calcium-mediated muscle contractions. The identification of scopoletin as an antispasmodic component of V. opulus was published in the Journal of Medicinal Chemistry in 1967 (Jarboe et al.).
• Viopudial: A sesquiterpene that contributes to antispasmodic action. Both scopoletin and viopudial have been determined to be responsible for the uterine relaxant activity of V. opulus. Viopudial has not been found in black haw bark, which may account for its weaker activity. Viopudial was described as a "hypotensive and smooth muscle antispasmodic" in research published in the Proceedings of the Society for Experimental Biology and Medicine in 1972 (Nicholson et al.).
• Viburnin: An antispasmodic bitter specific to the uterus and peripheral vasculature.
• Catechin and Epicatechin: Their presence is required for differentiation of cramp bark from Viburnum prunifolium; they largely contribute to the astringent activity of cramp bark.
• Proanthocyanidins: Have demonstrated gastroprotective effects via an increase in endogenous nitric oxide generation, suppression of lipid peroxidation, and mobilization of antioxidant activity.
• Salicylates (methyl salicylate / salicin): The bark contains methyl salicylate, which is a weak-acting precursor to the salicylic acid used in aspirin, but much less irritating to the gastric mucosa. Salicylates are anti-inflammatory and analgesic. Coumarins (scopoletin and scopaline) are uterine relaxants, with scopoletin being especially antispasmodic.
• Hydroquinone glycosides (arbutin): Hydroquinone glycosides (arbutin) have emmenagogue effects.
• Tannins: Tannins are astringent and may reduce excessive blood loss during menstruation.
• Valerianic (valeric) acid: Associated with the characteristic odour of the bark, noted as early as the 19th century; the bark is known to contain valerianic acid and yields its properties to water or diluted alcohol.

Overall, cramp bark is regarded as a powerful smooth and skeletal muscle antispasmodic, and hypotensive due to peripheral vasodilation caused by arterial smooth muscle relaxation.

4. Mechanisms of Action

The pharmacological actions of cramp bark are attributed primarily to its coumarin and sesquiterpene constituents acting on smooth and skeletal muscle tissue.

Antispasmodic / Smooth Muscle Relaxation

Evidence for antispasmodic effects derives primarily from in vitro studies demonstrating calcium channel antagonism by scopoletin and spasmolytic activity of viopudial in isolated tissue preparations. Several Viburnum spp., including V. opulus, have produced uterine relaxation in isolated rat tissues.

Coumarins (scopoletin, scopaline) are uterine relaxants. Cramp bark (Viburnum opulus) is considered the most potent uterine antispasmodic of the various Viburnum species because it contains more of the antispasmodic constituent scopoletin and also has viopudial. Scopoletin is a derivative of coumarin. Coumarins are known to ease muscle tension, and have also been found to reduce pain, inflammation, and uric acid levels. The bark also contains methyl salicylate, a weak-acting precursor to the salicylic acid found in aspirin for pain-relieving and anti-inflammatory effects.

Hypotensive Action

The hypotensive effect of cramp bark is due to peripheral vasodilation caused by arterial smooth muscle relaxation. Viopudial, in particular, was characterized in experimental research as both a hypotensive agent and a smooth muscle antispasmodic (Nicholson et al., 1972).

Gastroprotective Action

The tannins in V. opulus bark bind mucous proteins after intragastric administration, causing them to precipitate and thereby cover and protect sensitive stomach cells. Consequently, local pain is decreased, blood vessels are constricted, the secretion of gastric juice is decreased, and membrane density is increased, resulting in decreased inflammation.

Antioxidant Activity

The genus has been reported to possess antinociceptive, relaxant, spasmolytic, hepatoprotective, hypoglycemic, antioxidant, antiacetylcholinesterase, and anticarcinogenic potential. In cell-based studies, V. opulus demonstrated anti-inflammatory, anti-obesity, anti-diabetic, osteogenic, cardio-protective, and cytoprotective properties. These findings, however, are primarily derived from in vitro or animal studies and have not been confirmed in human clinical trials.

5. Scientific Evidence by Area of Use

5.1 Dysmenorrhoea (Menstrual Cramps)

Traditional basis: Cramp bark has a long history of use in folk medicine, especially among Native Americans and European herbalists, primarily for treating muscle spasms, menstrual cramps, and general pain relief. Traditionally, the bark was brewed into teas or tinctures for its antispasmodic and sedative properties.

Scientific evidence: There are no clinical trial reports for premenstrual syndrome; only the folk medicine use, as antispasmodic, in menstrual cramps, dysmenorrhea, and miscarriage prevention. Folk uses for cramp bark include treatment of painful menstruation and prevention of miscarriage, but no clinical trials are available to support these uses.

While cramp bark has centuries of traditional use for menstrual cramps, modern clinical research on its efficacy remains limited but promising. A study evaluating a homeopathic preparation of Viburnum opulus 3X for primary dysmenorrhea found that participants experienced significant reduction in pain intensity and duration compared to baseline measurements, and the treatment was well-tolerated with no adverse effects reported. This single study involved a highly diluted homeopathic preparation, which substantially limits any conclusions that can be drawn about the effect of cramp bark itself.

In a rat model of surgically induced endometriosis, V. opulus methanol and ethanol extracts administered at 100 mg/kg doses reduced post-treatment volumes of cystic and vascularised endometriotic implants by 67.6 mm³ and 66.7 mm³, respectively. This was a preclinical animal study (published in Journal of Ethnopharmacology, 2016, Saltan et al.) and does not constitute clinical evidence in humans.

Evidence strength: The antispasmodic mechanism is supported by in vitro and isolated-tissue pharmacological studies, and by the identification of scopoletin and viopudial as active constituents. However, there is an absence of published randomised controlled trials in humans evaluating cramp bark for dysmenorrhoea. The overall clinical evidence is rated as very weak.

5.2 Ureteral Stones (Kidney Stone Expulsion)

Traditional basis: The fruits of V. opulus have been consumed as food and applied as folk remedy in Europe and Asia. The fruits have been reported to be utilized for the treatment of kidney and bladder infections. In Turkish folk medicine, the juice obtained by squeezing the fruits is taken orally to pass kidney stones.

Preclinical evidence: In an animal study investigating the effects of different extracts of V. opulus fruit on urolithiasis, lyophilized V. opulus juice was found to have a preventive effect in rats with sodium oxalate-induced urolithiasis. The results obtained in that study provided scientific evidence for the traditional usage of V. opulus on passing kidney stones in Turkish folk medicine.

Human (retrospective) study: A retrospective study was conducted to evaluate the efficacy of Gilaburu (Viburnum opulus) extract in the treatment of distal ureteral stones <10 mm. Data of 103 patients were retrospectively analyzed. Patients were divided into two groups: those given V. opulus 1000 mg peroral 3×2 and diclofenac 50 mg peroral on-demand (n=53), and those given only diclofenac sodium 50 mg peroral on-demand (n=50). The rate of stone expulsion was significantly higher (82% vs. 66%, p=0.026), and elapsed time to stone expulsion was significantly shorter (9±1.8 vs. 14±2.3 days, p=0.018) in the V. opulus group. The need for additional treatment and analgesic requirement was less in the V. opulus group. The authors concluded that V. opulus is an herbal treatment alternative that facilitates the passage of ureteral stones <10 mm, but that prospective, randomised studies are needed to support these results.

Cramp bark may also be used for spasmodic tissue states in the bladder. This is particularly noted for ureteral stones: the smooth muscle contraction that often occurs in this condition is relaxed by cramp bark, which facilitates the passage of ureteral stones.

Evidence strength: The single human study was retrospective in design and used a fruit extract rather than the bark preparation typically sold as a supplement; this limits its applicability. Preclinical data are supportive. Prospective randomised trials are lacking. Evidence is preliminary.

5.3 Threatened Miscarriage / Uterine Spasm in Pregnancy

When there is uterine cramping in the absence of cervical dilatation, cramp bark (Viburnum opulus) and black haw (Viburnum prunifolium) are used to arrest uterine spasm. These herbs have a long history of use as spasmolytics during pregnancy, especially for miscarriage, dating back well over a hundred years by Western herbalists, and even longer by Native American tribes.

Evidence strength: No human clinical trials have been conducted. Evidence is based entirely on traditional use and Eclectic practice. The pharmacological plausibility is supported by the demonstrated uterine relaxant properties of scopoletin and viopudial in isolated tissues.

5.4 Gastrointestinal Cramping

Cramp bark is sometimes used for colic or irritable bowel syndrome as it reduces pain and cramping caused by infection or indigestion in the gastrointestinal tract. The fruits of V. opulus have been used in folk medicine for a wide range of conditions including digestive problems. Preclinical research has investigated gastroprotective effects of the plant's proanthocyanidins in animal models, though no human clinical trials are available for this indication.

Evidence strength: Preclinical only. No clinical trials.

5.5 Hypertension and Cardiovascular Effects

The constituent viopudial was characterised in early pharmacological research (Nicholson et al., 1972) as a hypotensive agent. The hypotensive effect is attributed to peripheral vasodilation caused by arterial smooth muscle relaxation. Folk uses for cramp bark include treatment of heart disease and hypertension, but no clinical trials are available to support these uses.

Evidence strength: Pharmacological mechanism identified in vitro; no clinical trials in humans.

5.6 Musculoskeletal Pain and Spasm

Cramp bark can be used both internally and topically to relieve cramps (especially menstrual and uterine and ovarian pain), asthma, and hypertension. Muscle spasms, pain and cramping in any area can benefit from its use including back and leg pain, arthritis, and polymyalgia. These applications are supported by traditional use and the broad antispasmodic pharmacology of scopoletin and viopudial, but remain unverified by human clinical trial.

Evidence strength: Traditional use and in vitro pharmacological data; no clinical trials.

5.7 Respiratory Conditions (Asthma, Bronchospasm)

Cramp bark can be used for bronchial spasm that can sometimes occur with an enduring post-viral cough. Folk uses for cramp bark include treatment of asthma. The theoretical basis is the general antispasmodic action of the bark on smooth muscle in the bronchial mucosa.

Evidence strength: Traditional use only; no clinical evidence.

5.8 Antidiabetic and Other Metabolic Effects

In vitro (test-tube) and animal studies suggest that cramp bark may help prevent kidney stones and type II diabetes. A 2021 study published in Antioxidants (Kajszczak et al.) investigated the glycoside hydrolase and non-enzymatic glycation inhibitory potential of V. opulus fruit in vitro, suggesting potential relevance to blood-sugar regulation. Viburnum opulus is used for muscle cramps, diabetes, high blood pressure, and kidney stones, but there is no good scientific evidence to support these uses.

Evidence strength: In vitro and animal only; no clinical trials in humans.

6. Body Systems and Health Areas

Based on traditional use, pharmacological research, and the limited clinical literature, cramp bark has been associated with the following body systems:

• Female Reproductive System: Primary area of use — uterine antispasmodic, dysmenorrhoea, threatened miscarriage, postpartum afterpains, endometriosis (preclinical).
• Musculoskeletal System: Skeletal and smooth muscle spasm, back pain, leg cramps, arthritis-associated pain.
• Urinary System: Ureteral stone expulsion (retrospective clinical study), bladder spasm, enuresis, diuresis.
• Cardiovascular System: Peripheral vasodilation, hypotensive effects (pharmacological data only).
• Digestive System: Gastrointestinal cramping, colic, gastroprotection (preclinical).
• Respiratory System: Bronchospasm, asthma (traditional use).
• Nervous System: Nervine relaxant properties attributed in traditional contexts.

Cramp bark best lends its therapeutic actions for conditions that present with constricted and tense tissue states. These may present throughout the body in almost any organ system.

7. Dosage Forms and Reported Dosages

The bark of both Viburnum opulus and related species is used medicinally and may be decocted, tinctured, or encapsulated as crude herb.

Tincture

Tincture (1:5 in 40%): Take between 4–8 mL in a little water up to 3 times a day. A tincture (1:5; 45%) at 5–10 mL three times daily has been described; for acute conditions, up to 5 mL every half hour or 30 mL every 3–4 hours. For a 1:2 liquid extract, 2–4.5 mL per day or 15–30 mL per week is cited; for acute dysmenorrhoea specifically, 4–8 mL three times daily using a 1:5 extract.

Decoction

To make a decoction, place 2 teaspoons of dried material in one cup of boiling water, simmer gently for 15–20 minutes, and drink hot 3 times a day.

Dried Powder (Capsule/Tablet)

Powder: 2–4 g three times daily.

Dosages Used in Clinical Research

In the retrospective clinical study on ureteral stones, V. opulus extract was administered at 1000 mg peroral 3×2 (i.e., 1000 mg taken twice per dosing interval, three times daily) alongside diclofenac 50 mg as needed. This study used a fruit extract rather than bark, so this dosage cannot be directly applied to bark preparations.

Clinical studies are generally lacking to provide standardized dosing guidance.

8. Safety Considerations and Drug Interactions

General Safety Profile

Contraindications have not yet been formally identified in the available literature. There is not enough reliable information to know with certainty whether Viburnum opulus is safe to use or what all the side effects might be.

Pregnancy and Lactation

Information regarding cramp bark safety in pregnancy and lactation is currently unavailable; therefore, avoidance of use in pregnant or lactating women is recommended in some references. There is not enough reliable information to know if Viburnum opulus is safe to use when pregnant or breast-feeding. This is a significant consideration given that the plant has paradoxically also been used as a uterine antispasmodic during pregnancy to prevent miscarriage — the two traditional indications (uterine stimulation via emmenagogue compounds and uterine relaxation via antispasmodic constituents) are pharmacologically contradictory, and no clinical safety studies have resolved this ambiguity.

Salicylate Content

Because cramp bark contains naturally occurring salicylates (aspirin-related compounds), individuals with aspirin allergies should use caution.

Coumarin Content and Anticoagulant Interactions

Cramp bark contains coumarins, which may have mild blood-thinning effects, so caution is advised in those taking anticoagulant medications.

Fruit vs. Bark Toxicity

Fresh berries are considered toxic. Medicinally, only the bark is used in the preparations described above; the berries and other plant parts have distinct chemical profiles and should not be considered equivalent to the bark.

Adulteration

Widespread adulteration of Viburnum spp. preparations with Acer spicatum (mountain maple) yielded varying results in research trials conducted in the early 20th century regarding the efficacy of Viburnum opulus. This is a documented quality-control concern that may affect both historical research results and modern commercial preparations.

Conservation Status

According to the IUCN Red List of Threatened Plants Status, cramp bark is classified as 'least concern' due to its widespread distribution, stable populations, and no major threats.

References

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• Kızılay F, et al. The evaluation of the effectiveness of Gilaburu (Viburnum opulus L.) extract in the medical expulsive treatment of distal ureteral stones. Turk J Urol. 2019;45(63). PubMed PMID 30978165
• Kızılay F, et al. (full text). The evaluation of the effectiveness of Gilaburu (Viburnum opulus L.) extract in the medical expulsive treatment of distal ureteral stones. PMC7595025
• İlhan M, et al. Preclinical Evaluation of Antiurolithiatic Activity of Viburnum opulus L. on Sodium Oxalate-Induced Urolithiasis Rat Model. Evid Based Complement Alternat Med. 2014;2014:578103. PMC4137613
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