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Topical diclofenac is now about as evidence-based as it can get

 •  • by Paul Ingraham
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Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

Many times over the years I have written about scientific papers that were the “nail in the coffin” for some treatment of dubious value, finally confirming that it doesn’t work. Today I have the opposite: science that strikes me as the last word in positive results. (I cannot think of a good metaphor for the opposite, unfortunately. I tried. I tried hard!)

Although little is ever truly “proven” in science, sometimes we can achieve a good-enough confidence and can consider the matter closed. I believe the safety and efficacy of topical diclofenac (Voltaren, Pennsaid) has now reached that point.

To recap the basics, diclofenac is a non-steroidal anti-inflammatory drug in the same class as ibuprofen and acetylsalicylic acid. When used topically, it is considered safer because it limits dosage, putting the drug only where you need it.

And it is indeed safe, and it is indeed actually efficacious for its most obvious target: osteoarthritis. And likely for several other common musculoskeletal complaints (athough that is much further from “proven,” it’s a pretty safe bet).

This last surge of confidence comes from an enormous new review (da Costa et al.) of trials of common pain medications for osteoarthritis, pooling the results of almost 200 trials with over 100,000 study subjects.

The big loser in this review was opioid treatment: its modest benefit, “regardless of preparation or dose, does not outweigh the harm it might cause.” (And I’ll add some more perspective from another new paper, Jenkin et al.: for patients getting surgery for fractures, acetaminophen with a bit of codeine did just as much good as oxycodone! That is counter-intuitive!)

And the big winner in da Costa et al. was the star of our show today, topical diclofenac, which:

…seems to be effective and generally safer because of reduced systemic exposure and lower dose, and should be considered as first line pharmacological treatment for knee osteoarthritis.

And how about oral NSAIDs? Two were judged most effective, though somewhat risky thanks to their side effects: “Etoricoxib 60 mg/day and diclofenac 150 mg/day seem to be the most effective oral NSAIDs.” (But far from entirely safe!)

Writing about this stuff a decade ago, all the signs were genuinely encouraging, but I still felt like I was going on a limb that could snap at any time. But it did not snap. Importantly, da Costa et al. is not the first big review that rules in favour of topical diclofenac — it’s just the most recent and biggest yet. And that’s enough. I no longer feel like I’m out on a limb with this: topical diclofenac definitely works for many people, and I’m relieved to really and truly “know” that after years of cautiously endorsing it. Now I can endorse it recklessly!