The objective was to show the superiority of Comfrey root extract ointment (Kytta-Salbe® f; Merck Selbstmedikation GmbH) to placebo ointment in patients with acute upper or low back pain. The study was conducted as a double-blind, multi-centre, randomised clinical trial with parallel group design over a period of 5 ± 1 days. The patients (n = 120, mean age 36.9 years) were treated with verum or placebo ointment three times a day, 4 g ointment 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. The secondary efficacy variables were back pain at rest using assessment by patient on VAS, pressure algometry (pain-time curve; AUC over 5 days), global assessment of efficacy by the patient and the investigator, consumption of analgesic medication, and functional impairment measured with the Oswestry Disability Index.
There was a significant treatment difference between Comfrey extract and placebo regarding the primary variable. In the course of the trial the pain intensity on active standardised movement decreased on average (medians) about 95.2 % in the verum group and 37.8 % in the placebo group. The results of this clinical trial were clear-cut and consistent across all primary and secondary efficacy variables. Comfrey root extract showed a remarkably potent and clical relevant effect in reducing acute back pain. For the first time, also a fast acting effect of the ointment (1 hour) has been witnessed.
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