Comfrey

Ass ear, black root, blackwort, boneset, bruisewort, consound, gum plant, healing herb, knitback, knitbone, salsify, slippery root, Symphytum officinale, wallwort

The medicinal components of comfrey are derived from the fresh or dried root and leaves of Symphytum officinale. Also used are the leaves and roots of Russian comfrey, a hybrid of S.officinale and S. asperum.

Comfrey's also medicinal effect may result from its allantoin content, which promotes cell proliferation and enhances wound healing. The roots contain more allantoin (0.6% to 0.7%) than the leaves (0.30/0)' Other components include rosmarinic acid-also beheved to have anti inflammatory properties mucilage, and numerous pyrrolizidine alkaloids Pyrrolizidine alkaloids are converted in the liver to toxic metabohtes that have been linked to hepatotoxicity. The root contains a higher amount of pyrrolizidine alkaloids than the leaves.

Russian comfrey contains echimidine, which may be the most toxic pyrrolizidine alkaloid found in comfrey. Comfrey is available as alcohol-free root extract, compounded oil, cream, leaf extract, ointment, and root extract, in products such as Comfree.

Reported uses

Comfrey is used topically to treat bruises, sprains, joint inflammation, swelling, and ulcers. It's also used to help heal wounds.

Administration

• Ointments and other external preparations containing 5% to 20% dried herb: Daily dose not to exceed 100 mcg of pyrrolizidine alkaloids with 1,2 unsaturated necine structure; applied topically to intact skin.

Hazards

Adverse effects associated with the internal use of comfrey include pancreatic islet cell tumors, urinary bladder tumors, hepatoxicity, liver damage, venoocclusive disease, and cancer. There are no reported Interactions with the topical use.

Comfrey should not be consumed orally. Topical application should be limited to 10 days.

Safety Risk Several agencies, including the United States Pharma copoeia's expert advisory panel and the American Herbal Products Association, have identified comfrey preparations as potentially harmful because of reports of liver toxicity. Many countries have banned internal use of comfrey, so such use is highly discouraged.

Clinical considerations

• Advise patient that comfrey isn't recommended for internal use.
• If patient has ingested comfrey, monitor for signs and symptoms of hepatotoxicity, including abdominal distention, nausea, right upper quadrant abdominal pain, and an elevated liver function test. If patient is using comfrey to promote wound healing, monitor the wound being treated. Evaluate the possibility of an infectious cause of cellulitis or inflammation.
• Inform patient that external preparations shouldn't be applied to broken or abraded skin.
• Use of comfrey should be limited to 4 to 6 weeks per year, to prevent exposure to large amounts of pyrrolizidine alkaloids.
• Tell patient to remind prescriber and pharmacist of any herbal or dietary supplement that he's taking when obtaining a new prescription.
• Advise patient to consult his health care provider before using an herbal preparation because a treatment with proven efficacy may be available.

Research summary

The concepts behind the use of comfrey and the claims made regarding its effects have not yet been validated scientifically.