The objective of this trial was to investigate the efficacy of a Comfrey root extract cream in patients with acute upper or lower back pain. The study was conducted as a double-blind, multi-centre, parallel group design RCT over a period of 5 ± 1 days. The patients (n=120, mean age 36.9 years, 46.7 % female) were treated three times a day, 4 g cream per application. The trial included four visits.

The primary efficacy variable was the area-under-the-curve (AUC) of the Visual Analogue Scale (VAS) on active standardised movement values at visits 1 to 4. Among the secondary objectives were back pain at rest (VAS), pressure algometry (pain-time curve; AUC over 5 days), global assessment of efficacy by the patient and investigator, and functional impairment measured with the Oswestry Disability Index.

There was a significant treatment difference between verum and placebo. In the course of the trial the primary variable decreased on average (median) about 95,2 % in the Comfrey extract group and 37.8 % in the placebo group. The results separated by pain location show an equivalent effect of comfrey extract: Regarding pain at rest, in lower back pain a reduction of 98% were observed, in upper back pain 96.9%.

The results of this RCT were clear-cut and consistent across all variables. Comfrey root extract cream showed a remarkably potent and clinically relevant effect in reducing acute back pain. For the first time a fast-acting effect of the ointment (1 hour) was also witnessed in this trial.