Herpes zoster and pain.

Pain is frequently the most distressing symptom of herpes zoster. Pain occurs in most patients during the acute phase and sometimes continues as postherpetic neuralgia (PHN) for months or years after the rash has healed. Both the acute pain and the incidence and duration of postherpetic pain are influenced by the age of the patient and the distribution of the rash. The acute pain is probably related to neuronal inflammation induced by the replicating varicella-zoster virus and can be helped by antiviral agents and by steroids. As yet, the pathophysiology of PHN is poorly understood and may well be multifactorial, perhaps accounting for the two clearly different types of PHN described. Prevention of PHN is not possible but there are some data suggesting the use of antiviral agents during the acute phase may be helpful. Once PHN has become established conventional analgesics are ineffective and tricyclic antidepressants seem to be the optimal therapy.