Topical Analgesics


Topical analgesics are widely available – many without prescription – in a variety of application forms. Some are rubbed onto the skin to produce pain relief, but there are also plasters available on the market.

There is a number of possible definitions for topical analgesics since many different applications fall under this category.

 

Main categories of topical analgesics

Rubefacients:

traditional formulations based on salicylate and nicotinate esters, capsaicin and capsicumextracts and derivatives

NSAIDs:

diclofenac, felbinac, ibuprofen, ketoprofen, piroxicam, naproxen, flurbiprofen and other NSAIDs

A miscellaneous group:

including benzydamine, mucopolysaccharide polysulphate, salicylamide and cooling sprays

 

Other topical analgesics

5% lidocaine plaster:

The lidocaine plaster develops its analgesic efficacy based on two different principles:

  1. The device as such offers an immediate cooling and soothing mechanical protection against painful as well as non-painful stimuli. By protecting e.g. against the painful rub of clothing on the skin (allodynia), the plaster may contribute significantly to improving patients quality of life.
  2. Topical lidocaine effects on the membranes of peripheral endings of A- and C- nerve fibres were it blocks mainly pathologically over-excitable sodium channels. This blockade inhibits sodium ion influx which is needed to generate an action potential transmitting a signal towards to central nervous system. As a consequence of the targeted blockade the neuronal membrane is stabilised, ectopic discharges are reduced and peripheral nociception is inhibited (local analgesia). As a long-term consequence, reduction of peripheral input may counteract on central sensitization.
Nociceptors


The 5% lidocaine medicated plaster is indicated for neuropathic pain following a herpes zoster infection (post-herpetic neuralgia).