What is lidocaine patch 5% used for?

Its meant to treat. Post-Herpetic Neuralgia officially. But can be used for muscle and superficial pain like neuropathy or nerve entrapment pain.
Lidocaine patches. While it only has limited FDA indications, the FDA is supposed to only regulate what companies making health care related products can advertise so it is often not worth the substantial investment (millions) to apply and so there are many non-FDA indicated uses from sunburn to sprains and other areas of tenderness can be helped, but the dosing needs to follow the package insert regardless.