Although vidarabine was the first systemic antiviral drug for the treatment of acute herpes zoster, the agent now used most frequently is acyclovir, a far safer drug that became available a decade ago. However, even with widespread use of acyclovir, postherpetic neuralgia (PHN) remains a principal cause of postinfectious morbidity. Newer antiviral agents, such as famciclovir and valacyclovir, have recently been introduced for the treatment of uncomplicated herpes zoster. In a double-blind, randomized study, 500 mg of famciclovir three times daily for 7 days was compared with placebo; in a second study, 500 mg of famciclovir three times daily for 7 days was compared with 800 mg of acyclovir five times daily for 7 days. Famciclovir significantly reduced duration of viral shedding (P = 0.0001) and accelerated lesion resolution compared with placebo. Famciclovir was comparable to acyclovir for these acute parameters. Most importantly, famciclovir recipients lost PHN two times faster than those receiving placebo (P = 0.02 all patients; P = 0.004 patients > or = 50 years) resulting in a reduction in the median duration of PHN (56 days all patients; 100 days patients > or = 50 years). This reduction translated to a 3.5-month reduction in the median duration of PHN for patients 50 years or older, those at greatest risk for developing the most common complication of herpes zoster. Famciclovir 500 mg administered three times a day for 7 days is an effective and well-tolerated treatment for acute herpes zoster, and is the only oral antiviral agent proven to reduce the duration of PHN when administered during acute zoster infection.
Herpes zoster occurs rarely in immunocompetent children and infrequently in immunocompetent young adults. However, its incidence increases with age, particularly after age 50. Reactivation of varicella-zoster virus (VZV) is characterized by a rash and is generally accompanied by considerable pain, dysesthesias, and skin hypersensitivity. Chronic pain that is sometimes experienced after the rash has healed is referred to as postherpetic neuralgia (PHN), the most common complication of herpes zoster. Postherpetic neuralgia is often severe and, unfortunately, refractory to most forms of treatment. The incidence of PHN also increases dramatically with increased age. More than 50% of zoster patients over 60 years old will develop PHN, which may persist for months and even years. Thus, established PHN is difficult to manage, often causing serious morbidity, depression, and high costs in terms of consumption of healthcare resources. Currently, early antiviral treatment with famciclovir has shown promise of reducing the duration of PHN.
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