What is the mechanism and clinical use of topical lidocaine patches in focal neuropathic pain?

• A. Local sodium channel blockade reduces ectopic signaling with minimal systemic exposure
• B. Systemic analgesia via opioid receptors
• C. They increase nerve conduction
• D. Decrease inflammation via COX inhibition

Answer: (D)

Topical lidocaine patches work by delivering a local anesthetic directly to a restricted skin area, where it acts on voltage-gated sodium channels on peripheral nerves. By blocking these channels in nociceptive fibers, the patch reduces the initiation and propagation of nerve impulses, especially the abnormal, ectopic discharges that underlie focal neuropathic pain. Because lidocaine is absorbed slowly through intact skin, systemic exposure is limited, so the analgesia is localized with relatively few systemic side effects.

Clinically, this makes the patch useful for focal neuropathic pain conditions such as postherpetic neuralgia or localized peripheral neuropathies where the pain is confined to a discrete area and can be targeted with a patch. The patch is typically applied for several hours per day (often up to about 12 hours) and removed before applying a new one in a different location if needed. It does not work by COX inhibition or systemic opioid receptor activation, and it does not increase nerve conduction; its benefit comes from local blockade of nerve signaling.