Herbal Monograph
Bugleweed
Lycopus virginicus L.
Lamiaceae (Mint family)
Commission E-approved anti-thyroid herb — the herbal treatment of choice for mild hyperthyroidism with cardiac and nervous symptoms.
Overview
Plant Description
Erect, herbaceous perennial, 15-60 cm tall, arising from slender rhizomes and stolons. Stems square (characteristic of Lamiaceae), simple or sparingly branched, smooth to slightly pubescent, often purplish at base. Leaves opposite, sessile to short-petiolate, lanceolate to ovate-lanceolate, 3-10 cm long, coarsely serrate to irregularly toothed, with a few deeply cut lower leaves, glabrous to slightly pubescent, dark green, dotted with minute glands (aromatic oil glands). Flowers very small, white, sessile, in dense axillary whorls (verticillasters) at the nodes of the upper leaves; calyx 4-5-lobed; corolla tubular, 2-3 mm, white with purple spots, barely exceeding the calyx; 2 fertile stamens (characteristic of Lycopus, distinguishing it from Mentha which has 4). Fruit: four nutlets per flower, enclosed within the persistent calyx. The plant spreads vegetatively via stolons and can form dense colonies in wet habitats. Produces a characteristic mint-family aroma when crushed, though milder than most Lamiaceae.
Habitat
Wet to moist habitats: marshes, swamps, wet meadows, stream banks, pond margins, ditches, and moist woodland edges. Prefers partial shade but tolerates full sun in consistently moist soils. Thrives in neutral to slightly acidic soils. Typically found in the transition zone between aquatic and terrestrial habitats (riparian zone).
Distribution
Native to eastern North America, from Newfoundland and Quebec south to Florida and west to Minnesota and eastern Texas. Most common in the northeastern United States and southeastern Canada. L. europaeus is found throughout Europe and western Asia. Both species are common in their respective ranges and not considered threatened.
Parts Used
Aerial parts (herb) — Lycopus herba
Preferred: Fresh plant tincture (1:2) for maximum potency; dried herb tincture (1:5) or infusion for standard use
The entire above-ground plant (stems, leaves, flowers) harvested during flowering is the medicinal part. Both fresh and dried herb are used. Fresh plant preparations (fresh plant tincture, expressed juice) are preferred by some practitioners for maximum activity, as some of the hydroxycinnamic acid derivatives may degrade during drying. The dried herb retains adequate activity for clinical use. The German Commission E monograph specifies L. europaeus and L. virginicus herb.
Key Constituents
Hydroxycinnamic acid derivatives (phenylpropanoids)
The hydroxycinnamic acid derivatives, particularly rosmarinic acid and lithospermic acid, are the primary bioactive constituents responsible for bugleweed's anti-thyroid (antithyrotropic) activity. The mechanism involves multiple complementary pathways: (1) inhibition of peripheral T4-to-T3 conversion by 5'-deiodinase; (2) inhibition of TSH receptor antibody binding at the thyroid gland; (3) reduction of TSH-stimulated intracellular signaling (cAMP); and (4) decreased thyroidal iodine uptake. This multi-target anti-thyroid mechanism is the pharmacological basis for the traditional and Commission E-approved use of bugleweed for mild hyperthyroid conditions. The anti-thyroid activity is concentration-dependent and reversible upon discontinuation.
Flavonoids
The flavonoid fraction contributes to the anti-inflammatory, antioxidant, and mild anxiolytic properties of bugleweed. While not the primary anti-thyroid agents, the flavonoids support the overall therapeutic profile, particularly the calming/nervine effect that is clinically relevant in hyperthyroid patients experiencing anxiety, palpitations, and nervous excitability.
Terpenes and essential oil
The terpene fraction plays a minor role in the overall therapeutic activity of bugleweed. The low essential oil content differentiates it from aromatic Lamiaceae used primarily as carminatives or antimicrobials. Ursolic acid contributes to the anti-inflammatory profile.
Tannins and other phenolics
The tannin content provides mild astringent activity, contributing to the traditional hemostatic and tissue-toning applications. The overall tannin content is moderate — bugleweed is not primarily an astringent herb.
Herbal Actions
Reduces inflammation
Anti-inflammatory activity through multiple mechanisms: rosmarinic acid inhibits complement activation (C3 convertase inhibition), lipoxygenase, and cyclooxygenase pathways. Flavonoids (luteolin) inhibit COX-2 and pro-inflammatory cytokine production. The anti-inflammatory action is relevant both systemically and specifically in the context of autoimmune thyroid inflammation (Graves' disease), where it may reduce immune-mediated thyroid stimulation.
[1, 7]Supports and calms the nervous system
Bugleweed acts as a nervine relaxant, calming nervous excitability, reducing anxiety, and slowing heart rate. This nervine action is particularly valuable in the context of hyperthyroidism, where excessive thyroid hormone produces anxiety, tremor, insomnia, and palpitations. The nervine effect is mediated by the flavonoids (apigenin's GABAergic activity) and the overall reduction in circulating thyroid hormone. In Eclectic medicine, bugleweed was classified as a 'sedative to the heart and circulation.'
[4, 6]Tightens and tones tissue, reduces secretions
Mild astringent action from tannin content. Traditionally used for hemoptysis (coughing blood), excessive menstrual bleeding, and other mild hemorrhages. The astringent quality is moderate — bugleweed is not a primary astringent herb but the tannins contribute to tissue toning.
[4]Lowers blood pressure
Mild blood pressure-lowering effect, primarily indirect through reduction of sympathetic nervous system overactivation in hyperthyroid states and through direct vasodilatory effects of rosmarinic acid. Also slows heart rate (negative chronotropic effect), reducing cardiac output.
[1]Strengthens and tones the heart muscle
Traditionally described as a cardiac sedative rather than a stimulant — bugleweed calms the overactive heart. Reduces tachycardia, palpitations, and cardiac excitability. The Eclectic physicians specifically valued it for 'cardiac erethism' (excessive cardiac excitability) associated with hyperthyroidism or nervous origin.
[4, 5]Prevents or slows oxidative damage to cells
Significant antioxidant capacity due to the high rosmarinic acid content. Rosmarinic acid is one of the more potent natural antioxidants, scavenging superoxide, hydroxyl, and peroxyl radicals and chelating pro-oxidant metal ions.
[7]Therapeutic Indications
Endocrine System
Mild hyperthyroidism (Graves' disease, autonomous thyroid nodule)
The primary modern indication. The German Commission E approved Lycopus for 'mild thyroid hyperfunction with disturbances of the vegetative nervous system' based on the demonstrated ability of rosmarinic acid and lithospermic acid to inhibit multiple steps in thyroid hormone production and activation. Bugleweed reduces peripheral T4-to-T3 conversion, inhibits TSH receptor antibody binding, decreases thyroidal iodine uptake, and reduces TSH-stimulated cAMP. Clinical experience and open-label studies support its use for mild hyperthyroid symptoms including tachycardia, nervousness, tremor, and weight loss. It is NOT adequate as monotherapy for severe or thyrotoxic hyperthyroidism — it is appropriate for mild, subclinical, or early hyperthyroid presentations, often as an adjunct to conventional therapy or during the monitoring phase.
[1, 7]Thyroid-associated cardiac symptoms (palpitations, tachycardia)
Bugleweed is specifically indicated for the cardiac manifestations of hyperthyroidism: palpitations, tachycardia, and cardiac excitability. The combination of thyroid hormone reduction (reducing the adrenergic sensitization caused by excess T3/T4) with the direct nervine and cardiac-calming effects makes it particularly effective for this symptom cluster. This dual mechanism (endocrine + direct cardiac) is unique to bugleweed among thyroid-active herbs.
[1, 4]Nervous System
Anxiety and nervous excitability associated with hyperthyroidism
The nervine action of bugleweed is best contextualized as part of its overall anti-thyroid/calming profile rather than as a standalone anxiolytic. In patients with thyroid-driven anxiety (tremor, insomnia, nervous excitability, hypervigilance), bugleweed addresses both the cause (excess thyroid hormone) and the symptom (nervous system excitability). It is not typically used for anxiety of non-thyroid origin, where other nervines (passionflower, lemon balm) are preferred.
[6]Cardiovascular System
Functional tachycardia and palpitations (nervous heart)
The Eclectic physicians used bugleweed for 'cardiac erethism' — a rapid, bounding, excitable heart not necessarily due to thyroid disease but associated with nervous excitability, stress, and functional cardiac over-stimulation. Felter described the specific indication as 'a rapid, tumultuous heart action with precordial oppression and pain, cardiac irritability, and a sense of constriction.' This use predates the understanding of thyroid-cardiac connections and reflects the direct cardio-sedative activity.
[4, 5]Respiratory System
Hemoptysis and irritative cough
A secondary Eclectic indication. Bugleweed's mild astringent and hemostatic properties were used for cough with blood-streaked sputum (hemoptysis of non-serious origin) and irritative, dry cough. Ellingwood described it for 'hemoptysis from passive hemorrhage, chronic cough with bloody sputum.' Not a primary modern indication but reflects the astringent/hemostatic action.
[5]Reproductive System
Menorrhagia and metrorrhagia (excessive menstrual bleeding)
Traditional Eclectic use based on the astringent/hemostatic properties. Used for excessive menstrual bleeding, particularly when associated with nervous excitability or thyroid dysfunction. Not a primary modern indication.
[4]Energetics
Temperature
cool
Moisture
dry
Taste
Tissue States
heat/excitation, wind/tension
Bugleweed is cooling and mildly drying in energetic quality. In vitalist Western herbal energetics, it is specifically indicated for states of heat and excitation — the hot, rapid, anxious, tremulous presentation of hyperthyroidism. The cooling action reduces excess metabolic heat; the drying, astringent quality tones tissues that are 'leaking' or in excess secretion (excess sweating, hemoptysis, menorrhagia). The bitter taste reflects the phenolic acid content. Bugleweed is contraindicated in cold, hypofunction states (hypothyroidism) where its cooling, thyroid-suppressive quality would worsen the condition.
Traditional Uses
Eclectic medicine (19th-20th century American)
- Primary remedy for 'cardiac erethism' — rapid, excitable, tumultuous heart action
- Hemoptysis (coughing blood) of passive origin
- Chronic cough with blood-streaked sputum
- Excessive menstrual bleeding (menorrhagia)
- Nervous excitability with cardiac symptoms
- Intermittent fever (as an adjunct diaphoretic)
- Diabetes mellitus (Eclectic indication, not supported by modern evidence)
"The Eclectic physicians valued bugleweed primarily as a cardiac and pulmonary sedative. Felter and Lloyd (1898) in King's American Dispensatory describe it for 'irritable heart, cough, and hemoptysis,' noting its specific action on the 'heart and lungs, lessening the frequency and force of the pulse, allaying irritation, and controlling hemorrhage.' Ellingwood (1919) added that its specific indications included 'tumultuous heart action, precordial oppression, cardiac pain, chronic cough with bloody expectoration, and hemoptysis from passive causes.' The Eclectics did not understand the thyroid mechanism — they described its effects phenomenologically."
European phytotherapy (Commission E)
- Mild thyroid hyperfunction with disturbances of the vegetative nervous system (Commission E approved indication)
- Thyroid-related tachycardia and palpitations
- Premenstrual breast tension and pain (mastodynia) associated with thyroid dysfunction
- Autonomic nervous system disturbances with cardiac involvement
"The German Commission E monograph (1990) approved Lycopus virginicus and L. europaeus herb for the treatment of mild forms of thyroid hyperfunction with disturbances of the vegetative nervous system, provided no thyroid enlargement is present. This monograph reflects the European phytotherapy understanding of bugleweed as primarily an anti-thyroid agent, which emerged in the mid-20th century with the discovery that rosmarinic acid and lithospermic acid inhibit thyroid hormone metabolism. The European approach is more pharmacologically specific than the Eclectic empirical tradition."
[1]
Native American medicine
- Used by some eastern woodland tribes for fever, cough, and bleeding conditions
- Root and herb preparations for respiratory complaints
- General astringent and wound herb
"Native American use of Lycopus species was less extensive than the subsequent Eclectic adoption. Some tribes used the plant for fever and respiratory conditions, recognizing its mild astringent and calming properties. The extensive therapeutic development occurred primarily in the Eclectic tradition."
[8]
Modern Research
Anti-thyroid mechanism — rosmarinic acid and Lycopus
In vitro and in vivo studies characterizing the anti-thyroid mechanisms of Lycopus extracts and their constituents, particularly rosmarinic acid and lithospermic acid.
Findings: Lycopus extracts and isolated rosmarinic acid/lithospermic acid inhibit multiple steps in thyroid hormone metabolism: (1) inhibition of TSH receptor antibody (TRAb) binding to TSH receptors on thyroid cells; (2) reduction of TSH-stimulated cAMP accumulation in thyroid tissue; (3) inhibition of peripheral 5'-deiodinase (type I), the enzyme that converts T4 to the more active T3; (4) decreased thyroidal iodine uptake. The anti-thyrotropic activity appears to be primarily mediated by the oxidized derivatives of rosmarinic acid and lithospermic acid rather than the parent compounds.
Limitations: Much of the mechanistic work is in vitro or in animal models. The relative contribution of each mechanism in human clinical use is not fully delineated. The active metabolites (oxidized derivatives) are difficult to standardize in commercial preparations.
Commission E therapeutic monograph — clinical basis
The German Commission E evaluated clinical evidence supporting Lycopus for mild thyroid hyperfunction, forming the basis of the positive therapeutic monograph.
Findings: The Commission E concluded that Lycopus herb is effective for mild forms of thyroid hyperfunction with autonomic nervous system disturbances, based on pharmacological evidence (anti-thyrotropic, T4-to-T3 conversion inhibition), traditional clinical experience, and available clinical data. The monograph specifies that treatment should not be abruptly discontinued (rebound thyroid overactivity possible) and should not be used when thyroid enlargement is present.
Limitations: The Commission E monographs were based on expert consensus rather than systematic meta-analysis. Large-scale RCTs of Lycopus for hyperthyroidism are lacking. The evidence base is stronger for mechanism than for clinical outcomes.
[1]
Antioxidant activity of Lycopus species
Studies evaluating the antioxidant capacity of Lycopus extracts in relation to their rosmarinic acid content.
Findings: Lycopus species, particularly L. europaeus and L. virginicus, demonstrate potent antioxidant activity in DPPH, ABTS, and ORAC assays, correlating with their high rosmarinic acid content (among the highest of all Lamiaceae species tested). The antioxidant activity may contribute to the anti-inflammatory effects and to protection against oxidative stress associated with hyperthyroidism (excess thyroid hormone increases metabolic rate and reactive oxygen species production).
Limitations: In vitro antioxidant assays have limited predictive value for in vivo antioxidant effects. Clinical studies measuring oxidative stress biomarkers in bugleweed-treated patients are lacking.
[7]
Complement inhibition and anti-inflammatory activity
Studies investigating the ability of rosmarinic acid from Lycopus to inhibit complement activation.
Findings: Rosmarinic acid inhibits complement C3 convertase, reducing complement-mediated inflammation. This mechanism is particularly relevant in autoimmune thyroid disease (Graves' disease), where complement activation contributes to thyroid inflammation and tissue damage. The complement-inhibiting activity adds an immune-modulatory dimension to bugleweed's anti-thyroid profile.
Limitations: In vitro mechanism. Clinical significance of complement inhibition in Graves' disease patients using bugleweed has not been assessed in controlled trials.
[3]
Prolactin inhibition
Lycopus extracts have been shown to reduce prolactin levels in experimental models.
Findings: Lycopus europaeus extract reduces prolactin secretion, possibly through dopaminergic mechanisms. This anti-prolactin activity may contribute to the traditional use for premenstrual breast tension (mastodynia), which is often associated with relative hyperprolactinemia. The Commission E notes this as a secondary application.
Limitations: Limited clinical evidence for the anti-prolactin effect. Mechanism is less well-characterized than the anti-thyroid activity.
[7]
Preparations & Dosage
Tincture
Strength: 1:2 fresh plant in 50-60% ethanol (preferred); or 1:5 dried herb in 45% ethanol
Macerate fresh or dried bugleweed herb (aerial parts) in ethanol-water menstruum. Fresh plant tincture: 1:2 in 50-60% ethanol (preferred for stronger thyroid-suppressive activity). Dried herb tincture: 1:5 in 45% ethanol. Macerate for 4-6 weeks. Press and filter.
2-6 mL of 1:5 tincture, 3 times daily. For fresh plant tincture (1:2), reduce dose proportionally: 1-2 mL, 3 times daily. Start low and titrate based on thyroid function monitoring.
3 times daily.
Long-term use is typical for thyroid conditions (months to years), but requires ongoing thyroid function monitoring. Do NOT discontinue abruptly — taper gradually over 2-4 weeks to avoid rebound thyroid overactivity.
Not established. Not recommended for children without qualified practitioner supervision.
Fresh plant tincture is considered more potent than dried herb preparations by many practitioners, as some of the hydroxycinnamic acid derivatives may oxidize or degrade during drying. However, dried herb tinctures retain adequate clinical activity. CRITICAL: Do not stop bugleweed tincture abruptly in patients using it for thyroid conditions — gradual tapering over 2-4 weeks is recommended to avoid rebound thyroid hyperactivity.
Infusion (Tea)
Strength: 1-2 g dried herb per 250 mL water
Pour 250 mL of boiling water over 1-2 g of dried bugleweed herb. Cover and steep for 10-15 minutes. Strain.
One cup (250 mL), 2-3 times daily.
2-3 times daily.
Ongoing for thyroid conditions with monitoring.
Not established.
Infusion is the simplest preparation form. Adequate for mild symptoms but less potent than tincture for thyroid management. May be useful as an adjunct or for patients who cannot tolerate alcohol. The taste is mildly bitter and acceptable to most patients.
Capsule / Powder
Strength: Crude dried herb powder, 500-1000 mg per capsule
Dried, powdered bugleweed herb encapsulated. Ensure product specifies Lycopus virginicus or L. europaeus and is standardized or quality-verified for rosmarinic acid content.
500-1000 mg of dried herb per capsule; 2-3 capsules daily (1-3 g total daily dose). Adjust based on thyroid function.
2-3 times daily with meals.
Long-term use with monitoring.
Not established.
Capsules provide convenient dosing but may be less potent than tincture or fresh-plant preparations. Look for products from manufacturers who verify rosmarinic acid content (>2% in dried herb).
[1]
Standardized Extract
Strength: Varies by manufacturer. Standardized to minimum rosmarinic acid content (typically ≥2%).
Commercially prepared concentrated extract of Lycopus herb, standardized to rosmarinic acid content. Available from European phytotherapy manufacturers.
Follow manufacturer's guidelines. Typical standardized extract dose: equivalent to 1-2 g of dried herb, 2-3 times daily.
2-3 times daily.
Long-term use with thyroid function monitoring.
Not established.
Standardized extracts offer more consistent dosing than crude herb preparations. European phytotherapy manufacturers (particularly German companies) produce standardized Lycopus preparations used in clinical practice. The standardization to rosmarinic acid content is important because the anti-thyroid activity correlates with this constituent.
Safety & Interactions
Class 2c
Not to be used with specific medications (AHPA Botanical Safety Handbook)
Contraindications
Bugleweed suppresses thyroid function. Use in hypothyroid patients would worsen the condition, potentially leading to myxedema. This is the most important contraindication.
The Commission E specifically contraindicates Lycopus when thyroid enlargement is present. Thyroid-suppressive activity in the context of goiter could worsen thyroid insufficiency and promote further compensatory gland enlargement.
Bugleweed's inhibition of T4-to-T3 conversion and thyroid function would interfere with thyroid hormone replacement, potentially causing iatrogenic hypothyroidism or requiring dose adjustments that are difficult to manage.
Bugleweed's inhibition of iodine uptake by the thyroid would interfere with radioiodine uptake scans and radioiodine therapy (I-131). Discontinue bugleweed at least 2 weeks before planned thyroid imaging or radioiodine treatment.
Drug Interactions
| Drug / Class | Severity | Mechanism |
|---|---|---|
| Levothyroxine (Synthroid, Levoxyl) and liothyronine (Cytomel) (Thyroid hormones) | major | Bugleweed inhibits peripheral T4-to-T3 conversion and decreases thyroid hormone production/activity. This directly opposes the therapeutic intent of thyroid hormone replacement, potentially causing iatrogenic hypothyroidism. |
| Methimazole (Tapazole) and propylthiouracil (PTU) (Antithyroid drugs (thionamides)) | moderate | Additive thyroid-suppressive effect. Bugleweed inhibits T4-to-T3 conversion and iodine uptake; thionamides inhibit thyroid peroxidase. Combined use could cause excessive thyroid suppression and hypothyroidism. |
| Radioiodine (I-131) and diagnostic thyroid imaging agents (Thyroid diagnostic/therapeutic agents) | major | Bugleweed decreases thyroidal iodine uptake, which would reduce the efficacy of radioiodine therapy and interfere with radioiodine uptake scan results. |
| Beta-blockers (propranolol, atenolol, metoprolol) (Beta-adrenergic blockers) | minor | Additive cardiac-slowing effect. Bugleweed reduces heart rate and cardiac excitability; beta-blockers do the same. Combined use could cause excessive bradycardia. |
| Sedative medications (benzodiazepines, barbiturates, zolpidem) (CNS depressants) | minor | Potential additive sedation. Bugleweed's nervine and calming effects may add to the sedation of pharmaceutical CNS depressants. |
Pregnancy & Lactation
Pregnancy
possibly unsafe
Lactation
insufficient data
PREGNANCY: The anti-thyroid activity of bugleweed makes it potentially unsafe during pregnancy, when maternal thyroid function is critical for fetal neurodevelopment. Suppression of maternal thyroid hormones could harm fetal brain development. Additionally, the effect of rosmarinic acid and lithospermic acid on fetal thyroid development is unknown. Avoid during pregnancy. LACTATION: Insufficient data. It is unknown whether the anti-thyroid constituents are excreted into breast milk. Given the critical role of thyroid hormones in infant neurodevelopment, avoidance during lactation is recommended as a precautionary measure.
Adverse Effects
References
Monograph Sources
- [1] German Commission E. Commission E Monograph: Lycopi herba (Bugleweed herb). Bundesanzeiger (Federal Gazette), Germany (1990)
- [2] Gardner Z, McGuffin M (eds.). American Herbal Products Association's Botanical Safety Handbook, Second Edition: Lycopus virginicus. CRC Press, Boca Raton (2013)
Clinical Studies
- [3] Auf'mkolk M, Ingbar JC, Kubota K, Amir SM, Ingbar SH. Extracts and auto-oxidized constituents of certain plants inhibit the receptor-binding and the biological activity of Graves' immunoglobulins. Endocrinology (1985) ; 116 : 1687-1693 . PMID: 2579856
Traditional Texts
- [4] Felter HW, Lloyd JU. King's American Dispensatory, 18th Edition: Lycopus. Ohio Valley Company, Cincinnati (1898)
- [5] Ellingwood F. American Materia Medica, Therapeutics and Pharmacognosy: Lycopus. Ellingwood's Therapeutist, Chicago (1919)
- [6] Hoffmann D. Medical Herbalism: The Science and Practice of Herbal Medicine. Healing Arts Press, Rochester, VT (2003)
- [7] Bone K, Mills S. Principles and Practice of Phytotherapy: Modern Herbal Medicine, Second Edition — Lycopus. Churchill Livingstone/Elsevier, Edinburgh (2013)
- [8] Moerman DE. Native American Ethnobotany. Timber Press, Portland, OR (1998)
Last updated: 2026-03-23 | Status: published
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