Systematic review of topical diclofenac for the treatment of acute and chronic musculoskeletal pain

Aim: The objective was to systematically review the efficacy and safety of topical diclofenac in both acute and chronic musculoskeletal pain in adults. Methods: We used standard Cochrane methods. Searches were conducted in MEDLINE, EMBASE and The Cochrane Register of Studies; date of the final search was November 2018. Included studies were randomized, double blinded, with ten or more participants per treatment arm. The primary outcome of "clinical success" was defined as participant-reported reduction in pain of at least 50%. Details of adverse events (AEs) were recorded. Results: For acute pain, 23 studies (5170 participants) were included. Compared to placebo, number needed to treat (NNT) for different formulations were as follows: diclofenac plaster, 4.7 (95% CI 3.7-6.5); diclofenac plaster with heparin, 7.4 (95% CI 4.6-19); and diclofenac Emulgel, 1.8 (95% CI 1.5-2.1). 4.1% (78/1919) reported a local AE. For chronic pain, 21 studies (26 publications) with 5995 participants were included. Formulations included gel, solution with or without DMSO, emulsion and plaster. A clinical success rate of similar to 60% (NNT 9.5 [95% CI 7-14.7]) was achieved with a variety of formulations. Local AEs (similar to 14%) were similar for both diclofenac and placebo. Conclusion: This systematic review of 11,000+ participants demonstrates that topical diclofenac is effective for acute pain, such as sprains, with minimal AEs. The effectiveness of topical diclofenac was also demonstrated in chronic musculoskeletal pain but with a higher NNT (worse) compared with acute pain. Formulation does play a part in effectiveness but needs further studies.