Minocycline may attenuate postherpetic neuralgia.

Postherpetic neuralgia (PHN) is a chronic pain syndrome and one of the most common complications of herpes zoster. Although the pathophysiological mechanisms involved in PHN are still largely unknown, it seems reasonable to assume that there are lesions of the peripheral afferent pain pathways and inflammation-induced damage to afferent ganglia in the spinal cord. Growing body of evidence indicates that the glial cells, particularly microglia (CNS macrophages) and astrocytes are activated following peripheral and central noxious insult and their activation is thought to play an important role in central sensitization. Glial modulators showed antiallodynic and antihyperalgesic properties in various models of experimental pain. Minocycline is a semisynthetic second generation tetracycline that exerts neuroprotection effect. It has been shown to be effective in preventing sciatic inflammatory neuropathy and intrathecal HIV-1gp120 associated pain behaviors. This agent has been used recently as a selective microglial inhibitor since it prevents microglial activation and disease progression in experimental allergic encephalomyelitis, an animal model of multiple sclerosis and other neurodegenerative diseases, such as amyotropic lateral sclerosis and Parkinson's disease. Therefore, we hypothesize that minocycline might attenuate postherpetic neuralgia by specifically inhibiting the activation and metabolism of glial cells.