Postherpetic neuralgia: impact of famciclovir, age, rash severity, and acute pain in herpes zoster patients.

New and previously reported analyses of the data from a placebo-controlled trial of famciclovir are reviewed in light of recently proposed recommendations for the analysis of pain in herpes zoster trials. The analyses examined the effect of famciclovir treatment on the duration of postherpetic neuralgia (PHN), which was defined as pain persisting after rash healing, pain persisting > 30 days after study enrollment, or pain persisting > 3 months after study enrollment; the baseline characteristics of patients in the famciclovir and placebo groups who developed PHN; the impact of famciclovir treatment on the duration of PHN, while controlling for significant covariates; and the prevalence of PHN at monthly intervals from 30 to 180 days after enrollment. The results of these analyses indicated that greater age, rash severity, and acute pain severity are risk factors for prolonged PHN. In addition, they demonstrated that treatment of acute herpes zoster patients with famciclovir significantly reduces both the duration and prevalence of PHN.