Lidocaine Patch for Back pain: 4% beats 5% !

FDA approved Lidocaine 5% patch for Postherpetic Neuralgia (PHN). In the hospital setting however, I have seen these patches used for almost everything except PHN 🤣 : acute or chronic low back pain, shoulder pain, rib pain, you-name-it-pain. One of my enterprising patients even removed the patch from their lower back & placed it on the forehead for a headache. 🤨

Specifically for back pain, no proper large randomized controlled trials for the 5% Lidocaine patch (Lidoderm) exist, as summarized in this 2020 review paper. The only small randomized control trial in the list showed a placebo patch was as good as a 5% Lidocaine patch ! A study that I found interesting was a Randomized controlled non-inferiority study in 2017 comparing a OTC 4% Lidocaine + Menthol patch with prescription 5% Lidoderm patch & placebo patches for back pain & arthritis. The study concluded that the 4% patch was non-inferior to 5% patch AND CONSISTENTLY MORE SUPERIOR superior to placebo than the 5% patch. The authors believe that the Menthol can help deliver Lidocaine better to the skin.

Off-label usage of Lidocaine patches isn’t going away, often patients demand them too. I find them hit-or-miss – although I am not against a placebo effect. So why not just go cheaper. I now always prescribe a 4% Lidocaine patch ( or advise 4% Lidocaine + 1.25% Menthol patch if available ), especially when I realized that after using a 5% patch for recommended max 12-hours, 95% of the drug is unused & wasted anyway (Page 2 on the FDA package insert)

So, what I am saying is, if using a Lidocaine patch for non-PHN pain,for the limited benefits of such patches in general, I see no point using a 5% Patch instead of 4%. If not more, at similar bang for less bucks !

💡 To summarize why:

• Lidocaine 4% patch is cheaper than the 5% patch
• Lidocaine 4% is over the counter (OTC), while 5% patches are prescription only
• The only randomized controlled trial of 5% patch for chronic back pain did not show it any better than placebo
• Lidocaine 4% patch combined with 1.25% Menthol (Still cheap, Still OTC, (e.g. Amazon sells Lido+Menthol patches) is at least good as the 5% patch & perhaps more effective. Menthol with its additional pain-relief effect is also shown to improve Lidocaine delivery to the skin