Comfrey by Hawaii Pharm

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Angina. Although there has been interest in using oral comfrey for angina, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Back pain. It is unclear if topical comfrey is beneficial in patients with back pain. Details: Clinical research in patients with lower or upper back pain shows that applying a specific ointment (Kytta-Salbe f, Merck Selbstmedikation GmbH) containing comfrey root extract 35% as 4 grams three times daily for 5 days decreases pain approximately 2-fold when compared with placebo (44912). Other clinical research shows that applying a specific cream (Kytta-Balsam f, Merck Selbstmedikation GmbH) containing comfrey root extract 35% and methyl nicotinate 1.2% as 4 grams three times daily for 5 days decreases pain scores by 54% at rest and by 50% during active motion when compared with placebo. These improvements were 24% and 27%, respectively, when compared with methyl nicotinate alone (92570).
• Bronchitis. Although there has been interest in using oral comfrey for bronchitis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Bruises. It is unclear if topical comfrey is beneficial in patients with bruises. Details: Preliminary clinical research in adults with bruises from therapeutic subcutaneous enoxaparin injections shows that applying comfrey 10% ointment four times daily for 5 days reduces the average bruise size by 77% when compared with placebo. Topical comfrey also improved the bruise color (108668).
• Cancer. Although there has been interest in using oral comfrey for cancer, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Cough. Although there has been interest in using oral comfrey for cough, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Diarrhea. Although there has been interest in using oral comfrey for diarrhea, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Gastritis. Although there has been interest in using oral comfrey for gastritis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Menorrhagia. Although there has been interest in using oral comfrey for menorrhagia, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Osteoarthritis. It is unclear if topical comfrey is beneficial in patients with osteoarthritis. Details: Preliminary clinical research in patients with knee osteoarthritis shows that applying a specific ointment (Kytta-Salbe f, Merck Selbstmedikation GmbH) containing comfrey root extract 35% three times daily for 3 weeks decreases pain scores 4-fold to 5-fold more than placebo. Applying comfrey root extract ointment also improved functional scores when compared with placebo (44904). Other clinical research in adults with knee osteoarthritis shows that applying a specific cream (4Jointz, Arthritis Relief Plus Ltd) containing comfrey extract 10% to 20%, plus tannic acid, aloe vera gel, eucalyptus oil, and frankincense oil three times daily for 6-12 weeks decreases pain approximately 2-fold more than placebo. The combination product also improved stiffness and physical functioning when compared with placebo (44919,92571).
• Peptic ulcers. Although there has been interest in using oral comfrey for peptic ulcers, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Pharyngitis. Although there has been interest in using oral or topical comfrey for pharyngitis, there is insufficient reliable information about the clinical effects of comfrey for this purpose.
• Sprains. It is unclear if topical comfrey is beneficial in patients with sprains. Details: Preliminary clinical research in adults with acute ankle sprains shows that applying a specific ointment (Kytta-Salbe f, Merck Selbstmedikation GmbH) containing comfrey root extract 35% as 2 grams four times daily for 8 days reduces pain and swelling and improves ankle mobility when compared with placebo (44898). Other research in adults with acute ankle sprains also shows that applying the same ointment reduces pain and tenderness scores to a similar extent as diclofenac gel 1.16% (44902).
• Tuberculosis. Although there has been interest in using oral comfrey for tuberculosis, there is insufficient reliable information about the clinical effects of comfrey for this purpose. More evidence is needed to rate comfrey for these uses.

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POSSIBLY SAFE ...when used topically for less than 6 weeks on unbroken skin at a daily dose providing no more than 100 mcg of pyrrolizidine alkaloid (PA) constituents. PAs are absorbed through the skin (11990,44898,44902,92568).

POSSIBLY UNSAFE ...when used for extended durations or in high concentrations on unbroken skin. Topically, hepatotoxic pyrrolizidine alkaloids (PAs) in comfrey can be absorbed in quantities sufficient to cause toxicity with extended use for greater than 6 weeks or in quantities providing more than 100 mcg of PAs (11990,92568). ...when used topically on broken skin. PAs can be absorbed through broken skin. In countries where the PA content of comfrey is not regulated, including Australia and the United States, creams containing comfrey are required to include a warning not to use on broken skin (44950,44951).

LIKELY UNSAFE ...when used orally because of its potential for acute or chronic liver toxicity. Comfrey contains hepatotoxic pyrrolizidine alkaloids (PAs). Chronic ingestion of more than 1 mg daily for 2 weeks or more than 100 mcg daily for longer durations can cause liver disease. PAs may also be carcinogenic (11987,99068). The FDA has recommended removal of oral comfrey products from the market (11988).

PREGNANCY AND LACTATION: LIKELY UNSAFE
when used orally or topically. In addition to hepatotoxicity and possible carcinogenicity, the pyrrolizidine alkaloids (PAs) in comfrey might be teratogenic. PAs are absorbed through the skin (11987,11988,11990).

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CYTOCHROME P450 3A4 (CYP3A4) INDUCERS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, CYP3A4 inducers might increase the risk of adverse effects from the pyrrolizidine alkaloid constituents in comfrey.  Details CYP3A4 enzymes convert pyrrolizidine alkaloids, constituents of comfrey, to toxic metabolites (11990). Some case reports show that enzyme inducers, such as phenobarbital, seem to enhance the toxicity of comfrey (12841,12860).

HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.  Details Due to its pyrrolizidine alkaloid constituents, comfrey can cause hepatotoxic effects, including ascites, cirrhosis, hepatic fibrosis, hepatomegaly, and sinusoidal obstruction syndrome (11988,11990).

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General ...When used orally, comfrey may be unsafe. Topically, comfrey is generally well tolerated when applied to intact skin.
Most Common Adverse Effects:
Topically: Eczema, erythema, irritation, itching, rash.
Serious Adverse Effects (Rare):
All ROAs: Ascites, cirrhosis, death, hepatic fibrosis, hepatomegaly, pulmonary hypertension, and sinusoidal obstruction syndrome. These adverse effects are likely related to the pyrrolizidine alkaloid constituents of comfrey.

Dermatologic ...Topically, comfrey-containing creams and ointments may cause skin redness, irritation, itching, rash, and eczema (44902,44912,44917,44919,92566,92570,92571).

Hepatic ...The pyrrolizidine alkaloid constituents of comfrey can cause acute sinusoidal obstruction syndrome 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 associated with comfrey toxicity is 50%. However, specific toxic levels seem to vary among individuals (11990).

Pulmonary/Respiratory ...The pyrrolizidine alkaloid constituents of comfrey can damage the lungs, resulting in pulmonary hypertension (11987,11988,11990). A case report involving a 66-year-old female with known arterial hypertension, mild kidney insufficiency, and type 2 diabetes described severe partial respiratory insufficiency and pulmonary hypertension. The patient admitted to using a number of alternative therapies daily, including comfrey (44911).

Other ...Comfrey contains toxic pyrrolizidine alkaloids, which are carcinogenic and mutagenic (12841,12842).

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