Yarrow - Drug Monograph

Introduction

Yarrow (Achillea millefolium) is a flowering perennial plant belonging to the Asteraceae family that has been used for centuries in traditional medicine systems worldwide. While not an FDA-approved pharmaceutical drug, it remains a significant botanical medicine with a well-documented history of medicinal use. This monograph provides evidence-based information regarding its pharmacological properties, therapeutic applications, and clinical considerations.

Mechanism of Action

Yarrow contains multiple bioactive compounds that contribute to its pharmacological effects:

• Flavonoids (apigenin, luteolin): Exhibit anti-inflammatory, antioxidant, and spasmolytic properties
• Sesquiterpene lactones: Demonstrate anti-inflammatory and antibacterial activities
• Alkaloids (achilleine): Possess hemostatic properties through vasoconstriction and platelet aggregation enhancement
• Volatile oils (including chamazulene, borneol, and camphor): Display antimicrobial and anti-inflammatory effects
• Tannins: Provide astringent properties useful for wound healing

The combined action of these constituents results in yarrow's documented effects on the gastrointestinal tract, cardiovascular system, and inflammatory pathways.

Indications

• Minor wounds and bleeding: Topical application for hemostasis
• Gastrointestinal disorders: Dyspepsia, mild spasms, loss of appetite
• Inflammatory conditions: Topical use for skin inflammation, oral use for mild inflammatory conditions
• Women's health: Traditional use for menstrual disorders and discomfort
• Fever and common cold: Diaphoretic properties in traditional fever management

Dosage and Administration

• Tea/infusion: 1-2 grams dried herb in 150 mL boiling water, 3 times daily
• Tincture (1:5 in 45% alcohol): 2-4 mL three times daily
• Topical compress: 5-10 grams dried herb per liter of water
• Liquid extract (1:1 in 25% alcohol): 2-4 mL three times daily

• Pediatric use: Safety not established; not recommended
• Geriatric use: Standard adult dosing with caution due to potential drug interactions
• Renal/hepatic impairment: No specific dosing recommendations available

Pharmacokinetics

Limited human pharmacokinetic data exists for yarrow constituents:

• Absorption: Flavonoids and sesquiterpenes are absorbed orally with variable bioavailability
• Distribution: Limited data; constituents likely distribute throughout body tissues
• Metabolism: Hepatic metabolism via cytochrome P450 enzymes; specific isoenzymes involved require further investigation
• Elimination: Primarily renal elimination; some components may undergo enterohepatic recirculation
• Half-life: Not established for individual components

Contraindications

• Known hypersensitivity to plants in the Asteraceae/Compositae family (chrysanthemums, marigolds, daisies)
• Pregnancy (due to potential uterine stimulant effects)
• Lactation (insufficient safety data)
• Children under 12 years of age

Warnings and Precautions

• Photosensitivity: May increase sensitivity to sunlight due to furanocoumarin content
• Cross-reactivity: Patients with ragweed allergy may experience allergic reactions
• Uterine effects: Use with caution in women of childbearing potential due to potential emmenagogue effects
• Liver function: Monitor in patients with pre-existing liver conditions
• Surgery: Discontinue at least 2 weeks prior to elective surgery due to potential effects on bleeding

Drug Interactions

• Anticoagulants/Antiplatelets (warfarin, aspirin, clopidogrel): Potential increased bleeding risk due to coumarin content
• Lithium: May decrease lithium elimination, increasing lithium toxicity risk
• Sedatives (benzodiazepines, barbiturates): Additive CNS depression effects
• Antihypertensives: Potential additive blood pressure lowering effects
• Diuretics: May potentiate diuretic effects
• Cytochrome P450 substrates: May affect metabolism of various drugs

Adverse Effects

• Gastrointestinal discomfort (nausea, diarrhea)
• Dizziness
• Skin reactions (contact dermatitis, photosensitivity)

• Severe allergic reactions (anaphylaxis in sensitive individuals)
• Hepatotoxicity (with prolonged high-dose use)
• Increased bleeding tendency

Monitoring Parameters

• Baseline and periodic: Liver function tests, renal function
• During therapy: Bleeding parameters (if on anticoagulants), skin reactions
• Symptom monitoring: Gastrointestinal tolerance, allergic manifestations
• Drug interaction monitoring: Especially with anticoagulants, sedatives, and antihypertensives

Patient Education

• Inform healthcare providers about all herbal product use, including yarrow
• Discontinue use 2 weeks before surgical procedures
• Monitor for signs of allergic reaction, especially if known Asteraceae allergy
• Use sun protection due to potential photosensitivity
• Report any unusual bleeding or bruising
• Not for use during pregnancy or breastfeeding
• Keep out of reach of children
• Purchase from reputable sources to ensure product quality and authenticity

References

1. Applequist WL, Moerman DE. Yarrow (Achillea millefolium L.): A Neglected Panacea? A Review of Ethnobotany, Bioactivity, and Biomedical Research. Econ Bot. 2011;65(2):209-225.

2. European Medicines Agency. Assessment report on Achillea millefolium L., herba. London: EMA; 2016.

3. Nemeth E, Bernath J. Biological activities of yarrow species (Achillea spp.). Curr Pharm Des. 2008;14(29):3151-3167.

4. World Health Organization. WHO Monographs on Selected Medicinal Plants. Volume 2. Geneva: WHO; 2002.

5. Chandler RF, Hooper SN, Harvey MJ. Ethnobotany and phytochemistry of yarrow, Achillea millefolium, Compositae. Econ Bot. 1982;36(2):203-223.

6. Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Integrative Medicine Communications; 2000.

7. Barnes J, Anderson LA, Phillipson JD. Herbal Medicines. 3rd ed. London: Pharmaceutical Press; 2007.

8. Natural Medicines Comprehensive Database. Achillea millefolium. Therapeutic Research Center; 2023.