Efficacy of topical analgesia Zanthoxylum rhetsa in the treatment of primary knee osteoarthritis: A randomized, double-blind, positive-controlled clinical trial

Background

The essential oil from the pericarp (EOP) of Zanthoxylum rhetsa (Roxb.) DC. inhibits prostaglandin E₂, which is related to knee osteoarthritis (OA). However, there is no clinical report on its efficacy.

Objectives

To assess the efficacy of EOP in Z. rhetsa (ZR) spray as a novel spray compared to diclofenac (DF) spray in elderly individuals diagnosed with primary knee OA.

Methods

60 patients with unilateral knee pain over three months were randomly assigned to either the ZR spray (experimental) or DF spray (control) group. Each group applied the spray topically 3 times daily (2 mL each time) for 14 consecutive days. Follow-ups occurred after day 7 and after day 14. Primary outcomes included pain score measurements, with secondary outcomes focusing on WOMAC index scores.

Results

The ZR and DF spray groups did not significantly differ at baseline. ZR spray is the first to demonstrate non-inferior efficacy compared to DF spray, with no significant difference in the mean change of pain scores at rest after 10 min (effect size <0.2) and following a 20-m walk test (effect size <0.5), including walking time (effect size <0.2), as well as in WOMAC index scores (effect size <0.3) from baseline to the first and second visits. Additionally, patients treated with ZR spray required less oral medication from the first visit.

Conclusions

Analgesia and improved knee functionality provided by ZR spray are suitable for combined treatment in elderly patients with co-morbidities or limited oral NSAID medication due to increased risk.