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Comfrey Root Ointment Reduces Pain in Patients with Knee Osteoarthritis
Reviewed: Grube B, Grunwald J, Krug L, Staiger C. Efficacy of a comfrey root (Symphyti offic. radix) extract ointment in the treatment of patients with painful osteoarthritis of the knee: results of a double-blind, randomised, bicenter, placebo-controlled trial. Phytomed. 2007;14(1):2-10.

Rheumatic disorders have different causes (inflammatory, infectious, degenerative, metabolic) and are located at different parts of the body (joints, tendons, muscles, spine). The multitude of diseases and complaints is matched by an equally large number of therapeutic treatment options. Phytomedicines such as ointments applied topically have the benefit of being applied on target and have fewer or no adverse drug reactions compared to conventional pharmaceutical medications taken orally.

For many years, the leaves and roots of the traditional medicinal plant comfrey (Symphytum officinale, Boraginaceae) have been used both internally and externally in different forms of administration for the treatment of a variety of diseases (e.g., bone fractures, wounds, ulcers). Recently, several clinical trials have proven the efficacy of comfrey in the treatment of distortions, strains and sprains, and other muscle and joint complaints.1,2,3,4 The pharmacodynamics of preparations made from the root may be attributable to the presence of allantoin, rosmarinic acid, and other hydroxycinamon acid derivatives, as well as mucopolysaccharides.

The goal of this randomized, placebo-controlled, double-blind study performed in Berlin, Germany, was to investigate the effect of daily application of a comfrey root extract (Kytta-Salbe®f, Merck Selbstmedikation GmbH, Darmstadt, Germany) over a 3-week period in patients suffering from painful osteoarthritis of the knee. Patients were randomly allocated to 1 of 2 treatment groups and received either Kytta-Salbe or placebo. The patients were to massage into the knee a 6 cm long thread of comfrey ointment or placebo 3 times per day.

Kytta Salbe contains comfrey root liquid extract (1:2, ethanol 60% V/V, 35%), and the extract specification allows an allantoin content of 0.2–0.5% (m/m). A special procedure removes more than 99% of the potentially hepatotoxic pyrrolizidine alkaloids contained in S. officinale (specification: < 0.35 ppm in the proprietary medicinal product). The German Commission E monograph on comfrey root approves it for external use as treatment for bruising, pulled muscles and ligaments, and sprains. Further, the daily dose of applied salve should not exceed an equivalent of more than 100 mcg pyrrolizidine alkaloids with 1,2-unsaturated necine structure, including its N-oxides.5

A total of 220 patients participated in the study. Pain relief was the primary criterion for evaluation. The results of the study demonstrated a greater decline in total pain in the comfrey group (54.7%) compared to the placebo group (10.7%). The average difference of 44.0% between the groups was significant (P<0.001). The decline in pain at rest and pain on movement was similar and statistically different in the comfrey root ointment group (P<0.001). The patients’ diaries confirmed the significance seen in the pain parameters.

The WOMAC (Western Ontario and McMaster Universities) total score (a secondary criterion measuring pain, stiffness, and function) also improved similar to the pain scores. At the end of the trial, a reduction by 58.0% was recorded for the comfrey group versus 14.1% for the placebo group. The average group difference of 43.9% was significant (P<0.001). Other exploratory parameters (quality of life, mobility of the knee, clinical global impression, and global assessment of efficacy) revealed a significant superiority (P<0.001, each) of the comfrey group over the placebo group.

The results of this study suggest that Kytta-Salbe comfrey root ointment is well suited for the treatment of osteoarthritis of the knee. Pain was reduced, mobility of the knee was improved, and quality of life was increased. The authors conclude that because the comfrey root ointment was significantly superior to the placebo medication with regard to all the parameters, this study proves the therapeutic efficacy of the comfrey root ointment in the treatment of painful osteoarthritis of the knee.

—Jennifer Minigh
  1. Koll R, Buhr M, Dieter R, et al. Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distortions: results of a multicenter, randomized, placebo-controlled, doubleblind study. Phytomedicine. 2004;11:470–477.

  2. Predel HG, Giannetti B, Koll R, Bulitta M, Staiger C. Efficacy of a comfrey root extract ointment in comparison to diclofenac in the treatment of ankle distortions: results of an observer-blind, randomized, multicenter study. Phytomedicine. 2005;12:707–715.

  3. Kucera M, Barna M, Horacek O, Kovarikova J, Kucera A. Topical symphytum herb concentrate cream against myalgia: a randomized controlled double blind clinical study. Adv Ther. 2005;22:681–692.

  4. Staiger C. Beinwell – eine moderne Arzneipflanze [Comfrey – a modern herbal drug]. Z Phytother. 2005;26:169–173.

  5. Blumenthal M, Busse WR, Goldberg A, Gruenwald J, Hall T, Riggins CW, Rister RS, eds. Klein S, Rister RS, trans. The Complete German Commission E Monographs Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; Boston: Integrative Medicine Communications; 1998.