A topical comfrey extract outperformed placebo in the treatment of lower back pain, according to a new study published in the British Journal of Sports Medicine.
This finding is probably not very surprising to practitioners of botanical medicine. This herb has traditionally been used as a topical pain reliever, and continues to be in lay botanical practice. Previous studies of the same comfrey gel (Kytta-Salbe, Merck) have shown similar effect versus placebo or topical NSAID in ankle injury and knee pain.
What may be a surprise to botanical prescribers, however, is that the source of funding for this trial is Merck, a company not usually known for interest in CAM practices. Given that they manufacture this topical preparation, perhaps it isn’t surprising to see company support for the trial.
As far as I am aware, this particular extraction is proprietary and may or may not be the same thing as the hot compresses used in traditional applications. The extract does appear to be available in the United States (bless you, Google).
As a topical application, comfrey is not known to be associated with any serious adverse effect. Comfrey should not be taken by mouth, as it contains pyrrizolidine alkaloids, which can cause serious liver toxicity.