Topical analgesics: lidocaine, capsaicin and topical NSAIDs

Topicals put the drug where the pain is and keep systemic exposure low. Know the lidocaine patch 12-hour rule, capsaicin 8% application times and repeat interval, and that topical NSAIDs come before oral NSAIDs in knee osteoarthritis.

1. Lidocaine 5% patch: three patches, 12 hours. Apply up to three patches to intact skin over the most painful area, once for up to 12 hours in any 24-hour period; absorption rises with area and duration ¹.
2. Topicals are second-line for neuropathic pain. The 2025 NeuPSIG update gives capsaicin 8% patches, capsaicin cream and lidocaine 5% plasters weak, second-line recommendations ²; the 2015 version limited topicals to peripheral pain with a local pain generator ⁶.
3. Lidocaine in frail patients: second line since 2025. NeuPSIG 2015 allowed lidocaine patches first line when systemic drugs raised safety concerns, particularly in frail older patients ⁶; the 2025 update ranks them second line, with very low certainty evidence (NNT 14.5) ².
4. Capsaicin 8% works by defunctionalizing nociceptors. It activates TRPV1, causing initial burning, then reduces TRPV1-expressing nerve endings, which re-emerge over several months ³.
5. Know capsaicin 8% application times. Up to four systems for 30 minutes on the feet in diabetic neuropathy, or 60 minutes for postherpetic neuralgia, repeated no more often than every 3 months, on intact skin ³.
6. Topical NSAIDs before oral in knee osteoarthritis. ACR/AF strongly recommends topical NSAIDs and advises considering them before oral NSAIDs ⁴. Topical diclofenac has a more favorable renal profile than oral, but at-risk kidneys still need monitoring ⁵.

Never apply capsaicin 8% or a lidocaine patch to broken skin, and handle capsaicin with nitrile gloves; wearing lidocaine patches continuously exceeds the labeled limit ¹³.

• Lidocaine patch schedule: 12 hours on, 12 hours off, maximum three patches ¹.
• Used lidocaine patches still contain drug; fold them and keep them away from children and pets ¹.
• NeuPSIG 2025 NNTs: capsaicin 8% patch 13.2; capsaicin cream 6.1 and lidocaine 5% 14.5, both very low certainty ².
• The burning during capsaicin application reflects TRPV1 activation before nociceptor defunctionalization ³.
• Capsaicin 8% can be repeated every 3 months as pain returns, not sooner ³.
• Topical diclofenac reduces but does not abolish renal risk in high-risk patients ⁵.
• NeuPSIG 2015 proposed topical treatment only for peripheral neuropathic pain with a presumed local pain generator, not for central pain ⁶.
• Topical NSAIDs follow the ACR principle that therapies with the least systemic exposure are preferable ⁴.

• Leaving lidocaine patches on around the clock to extend relief ¹.
• Repeating capsaicin 8% monthly because pain returns early ³.
• Starting oral NSAIDs first in an older adult with knee osteoarthritis and renal risk ⁴.
• Expecting a topical to help diffuse or central neuropathic pain without a local generator ⁶.