Comfrey Information & Purchase
Also Known As:
Ass Ear, Black Root, Blackwort, Bruisewort, Common Comfrey, Consolidae Radix, Consoude, Consoude Officinale, Consound, Consuelda, Grande Consoude, Gum Plant, Healing Herb, Herbe aux Charpentiers, Herbe à la Coupure, Knitback, Knitbone, Langue-de-Vache, Oreille d'Âne, Salsify, Slippery Root, Wallwort.
CAUTION: See separate listings for Black Root and Bugle.
Symphytum officinale. Family: Boraginaceae.
People Use This For:
Orally, comfrey is used as a tea for gastritis, ulcers, excessive menstrual flow, diarrhea, bloody urine, persistent cough, pleuritis, bronchitis, cancer, angina, as a gargle for gum disease, and pharyngitis.
Topically, comfrey is used for ulcers, wounds, joint inflammation, bruises, rheumatoid arthritis, phlebitis, gout, and fractures.
POSSIBLY SAFE ...when used topically short-term on unbroken skin at or below a daily dosage of 100 mcg of the hepatotoxic pyrrolizidine alkaloids (PA). Externally-applied pyrrolizidine alkaloids are absorbed through the skin.
LIKELY UNSAFE ...when used orally because of its potential for acute or chronic liver toxicity. Comfrey contains hepatotoxic PAs. Chronic ingestion of more than 1 mg per day for 2 weeks or more than 0.1 mg per day for longer periods can cause liver disease. PAs may also be carcinogenic. The FDA has recommended removal of oral comfrey products from the market.
PREGNANCY AND LACTATION: LIKELY UNSAFE ...when used orally or topically. In addition to hepatotoxicity and possible carcinogenicity, the PAs in comfrey might be teratogenic. PAs are absorbed through the skin.
INSUFFICIENT RELIABLE EVIDENCE to RATE Bruises and sprains. Preliminary clinical research suggests that applying comfrey topically might improve pain and tenderness of bruises, sprains, and painful conditions of the muscles and joints. More evidence is needed to rate comfrey for this use.
Mechanism of Action:
The applicable parts of comfrey are the leaf, rhizome, and root. Comfrey contains symphytine, lasiocarpine, and other pyrrolizidine alkaloids (PA) that are hepatotoxic and carcinogenic, mutagenic, and teratogenic. Hepatotoxic PAs cause veno-occlusive liver disease. They destroy and damage centrilobular hepatocytes of the liver and also destroy small branches of the hepatic vein. PAs can also damage the lungs, resulting in pulmonary hypertension. The PA content of comfrey varies with time of harvesting and plant age. The roots have 10 times higher concentrations of PAs than the leaves.
PAs are metabolized in the liver by the cytochrome P450 (CYP) enzyme system, specifically by CYP 3A4, to toxic dehydroalkaloids and pyrroles. Enzyme inducers such as phenobarbital seem to enhance toxicity. Pyrroles are excreted as N-acetyl cysteine conjugates. Some researchers speculate that early administration of N-acetylcysteine might reduce toxicity.
Metabolism is also affected by pregnane X receptor induction of CYP3A4. Genetic or drug-induced variation in CYP3A4 or pregnane X receptor activity can affect the degree of PA toxicity by increasing or decreasing its metabolism.
There are sufficient amounts of hepatotoxic PAs in herbal products to cause toxicity.
Orally, the major concern about comfrey is the hepatotoxic pyrrolizidine alkaloid (PA) content. These constituents are hepatotoxic, pneumotoxic, carcinogenic, and mutagenic. Comfrey can cause acute veno-occlusive disease characterized by sudden abdominal pain, vomiting, ascites, and hepatomegaly. In subacute disease, comfrey can cause ascites, hepatomegaly, abdominal pain, diarrhea, vomiting, and abdominal swelling. Chronic toxicity appears as asthenia and progressive ascites. Hepatic fibrosis and inflammation may resolve, but hepatic failure is common with more severe disease. This may occur as late as 2 years after the initial ingestion. Other signs and symptoms of pyrrolizidine toxicity include bile duct proliferation, fatty changes of the liver, fibrosis, cirrhosis, and vascular lesions (11988). The mortality of comfrey toxicity is 50%. However, toxicity seems to vary among individuals.
Topically, PAs can be absorbed in quantities sufficient to cause toxicity with extended use or in high concentrations
Interactions with Herbs & Supplements:
HEPATOTOXIC HERBS AND SUPPLEMENTS: Theoretically, comfrey might have additive effects with herbs that cause hepatotoxicity. Other products that might affect the liver include chaparral, bishop's weed, borage, kava, uva ursi, and others.
HEPATOTOXIC PYRROLIZIDINE ALKALOID (PA)-CONTAINING HERBS: Concomitant use is contraindicated due to the risk of additive toxicity. Herbs containing hepatotoxic PAs include alkanna, boneset, borage, butterbur, coltsfoot, comfrey, forget-me-not, gravel root, hemp agrimony, and hound's tongue; and the Senecio species plants dusty miller, groundsel, golden ragwort, and tansy ragwort.
HERBS THAT INDUCE CYTOCHROME P450 3A4 (CYP3A4): Theoretically, herbs that induce CYP3A4 might increase the conversion of hepatotoxic PAs to toxic metabolites, enhancing toxicity. Herbs that induce CYP3A4 include echinacea, garlic, licorice, St. John's wort, and schisandra.
Interactions with Drugs:
CYTOCHROME P450 3A4 (CYP3A4) INDUCERS Interaction Rating = Moderate Be cautious with this combination.
Theoretically, drugs that induce CYP3A4 might increase the conversion of comfrey to toxic metabolites, enhancing toxicity. Some drugs that induce CYP3A4 include carbamazepine (Tegretol), phenobarbital, phenytoin (Dilantin), rifampin, rifabutin (Mycobutin), and others.
HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs. Some drugs that can adversely affect the liver include acetaminophen (Tylenol), amiodarone (Cordarone), carbamazepine (Tegretol), isoniazid (INH), methotrexate (Rheumatrex), methyldopa (Aldomet), and many others.
Interactions with Foods:
Interactions with Lab Tests:
LIVER FUNCTION TESTS: The hepatotoxic pyrrolizidine alkaloids (PA) in comfrey might increase liver function tests including alkaline phosphatase, aspartic acid transaminase (AST, SGOT) alanine aminotransferase (ALT, SGPT), total bilirubin, gamma-glutamyltransferase, and lactate dehydrogenase .
Interactions with Diseases or Conditions:
BROKEN, DAMAGED SKIN: Contraindicated. Apply only to unbroken skin. Broken skin might result in exposure to high concentrations of hepatotoxic pyrrolizidine alkaloids (PA).
LIVER DISEASE: Theoretically, comfrey might exacerbate liver dysfunction in patients with liver disease.
No typical dosage.
Some products labeled common comfrey or Symphytum officinale actually contain the more toxic prickly comfrey (Symphytum asperum) or Russian comfrey (Symphytum x uplandicum) species.
General Certificate Of Analysis (COA) less manufacture date and batch number provided for different product strengths if the link is not available or manufacture date and batch number is required use the email us box to request Certificate Of Analysis (COA) emailed. Any questions about product or wholesale pricing for twenty five kilos or more. Please be sure to use product ID, Trade Name and Scientific Name.
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"These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease."