Comfrey root extract in combination with methylnicotinate in the treatment of acute upper or lower back pain: Results of a double-blind, placebo-controlled, multicenter, three-arm RCT

Several RCTs have confirmed the efficacy of comfrey root extract (Symphytum officinale L.) (CRE) in painful muscle and joint complaints. The topical pharmacotherapeutic approach has also included hyperaemising drugs to relax the contracted muscle area. Thus, the extract has also been used in combination with methylnicotinate (MN).

The objective was to show the superiority of a CRE plus MN cream (Kytta-Balsam® f) to MN and placebo cream in patients with acute upper or low back pain. In this RCT 379 patients were assigned to three groups (combination of 35% CRE plus 1.2% MN, n = 163; MN, n = 164; placebo, n = 52) and applied a 12 cm layer of cream 3 times daily for 5 days. The trial included four visits.

The primary efficacy variable was the AUC (area under the curve) of the VAS (Visual Analogue Scale) on active standardised movement values at visits 1 to 4. Patients performed standardised, muscle group specific tests. Secondary measures included back pain at rest, pressure algometry, consumption of analgesic medication, functional impairment measured with Oswestry Disability Index, and global assessment of response.

The AUC of the VAS on active standardised movement was markedly smaller in the combination treatment group than in the MN and the placebo group (ANOVA: p < 0.0001). The pairwise comparisons of the mean AUCs of VAS sums showed values 27% lower in favour of the combination compared to MN, and values 50% lower in favour of the combination compared to placebo. MN alone reached a reduction in this variable of 31% compared to placebo. All pairwise comparisons were statistically significant (t-test: p < 0.0001). The results were consistent across the primary and all secondary variables. Patients treated with the combination had significant superior reductions in pain scores and were more satisfied with the treatment effect.

The combination demonstrated superiority to the two other treatment arms, while methyl nicotinate displayed a considerable effect as well.