Post herpetic neuralgia pain may precede eruption of vesicles by 7 days and usually resolves within 3 months. Post herpetic neuralgia is defined as facial pain in the affected nerve distribution that remains 3 months after skin vesicles resolve. Dorsal root ganglion necrosis, presence of virus in the nerve and atrophy of the dorsal horn are thought to contribute to post herpetic neuralgia. Antiviral medications including acyclovir and the more bioavailable valaciclovir and famciclovir are used in the treatment of acute herpes zoster and may help to prevent development of post-herpetic neuralgia (PHN). A meta-analysis of 5 placebo-controlled trials showed that acyclovir reduced the incidence of pain at 6 months, with a number needed to treat of 6.3. Tricyclic antidepressants may also help to prevent PHN. A randomized trial of patients 60 years with or older with herpes zoster who were treated with amitriptyline versus placebo showed a 50% decrease in pain prevalence at 6 months in the group treated with amitriptyline. The use of steroids has also been suggested but this has not been shown be effective in preventing PHN.
Pain caused by post-herpetic neuralgia may be treated with neuropathic pain medications including anticonvulsants (gabapentin, pregabalin), antidepressants (TCAs), topical agents (lidocaine), capsacin and opioids. Sympathetic blockade, such as a stellate ganglion block) may be helpful if performed in the first year.
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