Cramp Bark (Viburnum opulus)

Cramp bark (Viburnum opulus) contains the antispasmodic compounds scopoletin and viopudial, which relax smooth and skeletal muscle tissue by inhibiting calcium-mediated muscle contractions. It has been used in European herbal medicine for centuries primarily to relieve uterine and menstrual cramping, though modern clinical trial evidence remains limited.

Origin & History

Cramp bark is the dried bark of Viburnum opulus L., a deciduous shrub native to Europe, northern Africa, and central Asia. 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.

Historical & Cultural Context

Cramp bark has been used in European traditional medicine for over 200 years as documented in the British Herbal Pharmacopoeia, primarily as an antispasmodic for menstrual cramps and muscle spasms. Native American and early European herbalists employed bark decoctions and tinctures for cramps, colic, and nervous conditions.

Health Benefits

• Traditional antispasmodic for menstrual cramps and muscle spasms - evidence based on historical use only, no clinical trials identified
• Potential antioxidant activity - preliminary evidence from in vitro assays (ORAC, FRAP, ABTS) showing radical scavenging capacity
• Traditional use for uterine pain relief - supported by 200+ years of European herbalism but lacks clinical validation
• May help with muscle relaxation - patent data suggests verbenalin content (~7.7% in extracts) as active marker but no human studies
• Traditional remedy for colic and nervous conditions - historical use documented in Native American and European herbalism without clinical evidence

How It Works

Scopoletin, a coumarin glycoside in cramp bark, acts as a smooth muscle relaxant by blocking voltage-gated calcium channels, reducing intracellular calcium availability needed for muscle contraction. Viopudial, a bitter iridoid, has demonstrated spasmolytic activity by modulating autonomic nerve signaling at smooth muscle tissue. Additionally, flavonoids such as amentoflavone may contribute antioxidant activity by scavenging reactive oxygen species via hydrogen atom transfer and single electron transfer mechanisms, as measured in ORAC, FRAP, and ABTS in vitro assays.

Scientific Research

No human clinical trials, RCTs, or meta-analyses on cramp bark were identified in the research. Available studies (PMC6684545, PMC7694363) focus only on phytochemical composition and in vitro antioxidant assays rather than human outcomes.

Clinical Summary

No peer-reviewed randomized controlled trials specifically evaluating cramp bark in human subjects for menstrual pain or muscle spasm relief have been identified in the published literature. Evidence for its antispasmodic effects derives primarily from in vitro studies demonstrating calcium channel antagonism by scopoletin and spasmolytic activity of viopudial in isolated tissue preparations. Its antioxidant capacity has been quantified in cell-free assays, but these findings have not been translated into clinical outcomes data. The overall evidence base remains at a traditional-use and preclinical level, warranting caution before drawing firm efficacy conclusions.

Nutritional Profile

Cramp Bark (Viburnum opulus) is a medicinal bark rather than a nutritional food source; macronutrient content (protein, fat, carbohydrate) is negligible in therapeutic preparations. Bioactive compounds drive its pharmacological interest: Scopoletin (coumarin glycoside) is the primary active constituent, reported at approximately 0.1–0.5% dry weight in bark extracts, acting as a smooth muscle relaxant. Viopudial (an iridoid) is present at trace levels and contributes to antispasmodic activity. Isovaleric acid and its esters (including borneol isovalerate) are volatile constituents identified in bark, contributing to muscle-relaxing properties. Chlorogenic acid and other hydroxycinnamic acid derivatives provide phenolic antioxidant activity, with total phenolic content reported at 15–40 mg GAE/g dry extract in preliminary assays. Tannins (hydrolyzable type) are present at approximately 2–4% dry weight, contributing astringent properties. Flavonoids including amentoflavone and kaempferol glycosides have been identified at low concentrations (<1% dry weight). Saponins are present in minor quantities. Vitamin C has been detected in the fruit (not bark) at approximately 50–80 mg/100g fresh weight. Mineral content of bark includes modest potassium, calcium, and magnesium, but concentrations are insufficient to contribute meaningfully to dietary intake. Bioavailability data is largely absent from clinical literature; scopoletin bioavailability is inferred from related coumarin pharmacokinetic studies suggesting reasonable oral absorption, but bark-specific human pharmacokinetic studies have not been published.

Preparation & Dosage

No clinically studied dosage ranges available due to absence of human trials. Commercial preparations include alcohol-free liquid extracts (1:3 w/v dry bark in glycerin-water) and bark powders, but standardization is limited. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Valerian, Passionflower, Magnesium, Black Cohosh, Ginger

Safety & Interactions

Cramp bark is generally considered well tolerated at typical herbal doses (300–500 mg dried bark extract, 2–3 times daily), with mild nausea and gastrointestinal upset reported at higher doses. Due to its uterine-relaxing spasmolytic activity, it is contraindicated in early pregnancy despite traditional use for threatened miscarriage, as the safety profile in pregnant women has not been established by clinical research. Its coumarin content (scopoletin) raises a theoretical interaction concern with anticoagulant medications such as warfarin, as coumarins can potentiate blood-thinning effects, though direct pharmacokinetic interaction studies are lacking. Individuals with aspirin sensitivity or salicylate intolerance should use caution, as Viburnum opulus bark contains salicin-related compounds.