Topical comfrey root extract in painful osteoarthritis: results of a randomized, double-blind placebo-controlled clinical trial

The aim of this randomized, double-blind, placebo-controlled clinical trial (COPA) was to demonstrate the therapeutic efficacy of a comfrey root extract ointment (Extr. Rad. Symphyti) in the treatment of patients with painful osteoarthritis of the knee. The trial was performed in accordance with the Declaration of Helsinki/Hong Kong 1989/Somerset 1996 as well as ICH-GCP Guidelines. 220 patients (153 women, 67 men, mean age 57.9 years) received daily 6g (3×2g) of either an active ointment (Kytta-Salbe® f, containing comfrey root fluid extract 1:2, 35.0g, extraction solvent ethanol 60% (v/v)) or a corresponding placebo, for 21 days.

In the course of the study, the VAS sum score (primary target variable) decreased by 51.6mm (54.7%) in the active therapy group and by 10.1mm (10.7%) in the placebo group. The mean group difference of 41.5mm or 44.0% points is significant (p <0.001). The WOMAC sum score (secondary target variable) decreased by 60.4 mm (58.0%) in the active therapy group and by 14.7mm (14.1%) in the placebo group. The mean group difference of 45.7mm or 43.9% points is significant (p<0.001). With regard to further exploratory target variables SF-36 (quality of life), angle measurement (knee mobility), CGI (clinical global impression) and global efficacy assessment by investigator and patient, a significant superiority was also demonstrated (p<0.001, respectively) for the phytotherapeutic agent versus placebo. A total of 22 AEs occured in 22 patients (7 in the active therapy group, 15 in the placebo group). None did present as adverse drug reaction in the active therapy group.

Conclusion: The comfrey root extract ointment reduced the symptoms of osteoarthritis of the knee significantly. The therapy lead to reduction of pain, improved knee mobility and better quality of life. Therefore, the present clinical trial has demonstrated that the topical application of a comfrey root extract is a sensible and safe treatment option for patients with painful osteoarthritis.

Reference: Grube B, Grünwald J, Krug L, Staiger C (2007) Phytomedicine 14: 2–10.