Charles E. Argoff, MD, Professor of Neurology and Director of the Comprehensive Pain Center, Albany Medical Center, describes the side effect profile of topical NSAIDs, which is exactly the same as for oral NSAIDs. The incidence of side effects however tends to be lower.
Safety and efficacy of topical diclofenac sodium 1% gel in knee osteoarthritis: a randomized controlled trial.
Baraf HS, Gold MS, Clark MB, Altman RD. Phys Sportsmed. 2010 Jun;38(2):19-28.
The effects of topical viscous lignocaine 2% versus per-rectal diclofenac in early post-tonsillectomy pain in children.
Rhendra Hardy MZ, Zayuah MS, Baharudin A, Wan Aasim WA, Shamsul KH, Hashimah I, Suan YA. Int J Pediatr Otorhinolaryngol. 2010 Apr;74(4):374-7. Epub 2010 Feb 2.
Systemic bioavailability of topical diclofenac sodium gel 1% versus oral diclofenac sodium in healthy volunteers.
Kienzler JL, Gold M, Nollevaux F. J Clin Pharmacol. 2010 Jan;50(1):50-61. Epub 2009 Oct 19.