The relative efficacy of topical non-steroidal anti-inflammatory drugs and capsaicin in osteoarthritis: a network meta-analysis of randomised controlled trials

OBJECTIVE: To compare the efficacy of topical non-steroidal anti-inflammatory drugs (NSAIDs) with topical capsaicin for pain relief in osteoarthritis (OA). DESIGN: A systematic literature search was conducted for randomised controlled trials (RCTs) examining any topical NSAID or capsaicin in OA. Pain relief at or nearest to 4 weeks was pooled using a random-effects network meta-analysis (NMA) in a Frequentist and Bayesian setting. Analysis was conducted for all trials and for trials using drugs listed as licensed for OA in the British National Formulary (BNF). RESULTS: The trial network comprised 28 RCTs (7372 participants), of which 17 RCTs (3174 participants) were included in the as licensed analyses. No RCTs directly compared topical NSAIDs with capsaicin. Placebo was the only common comparator for topical NSAIDs and capsaicin. Frequentist and Bayesian effect size (ES) estimates were in agreement. Topical NSAIDs were statistically superior to placebo overall (ES 0.30, 95% confidence interval [CI] 0.19 to 0.41) and as licensed (ES 0.32, 95% CI 0.24 to 0.39). However, capsaicin was only statistically superior to placebo when used at licensed doses (ES 0.41, 95% CI 0.17 to 0.64). No significant differences were observed in pain relief between topical NSAIDs and capsaicin (overall: ES 0.04, 95% CI −0.26 to 0.33; as licensed: ES-0.09, 95% CI −0.34 to 0.16). CONCLUSIONS: Current evidence indicates that topical NSAIDs and capsaicin in licensed doses may be equally effective for pain relief in OA. Whether the equivalence varies between individuals remains unknown.