One-year follow-up of zoster-associated pain in 764 immunocompetent patients with acute herpes zoster treated with famciclovir (FAMILIAR study)

Background Herpes zoster (HZ), a reactivation of varicella zoster virus manifested by skin blisters and neuralgia, can lead to postherpetic neuralgia in 10-20% of affected subjects. Method In this study, a cohort of 764 patients with HZ was treated with 1500 mg/day of famciclovir for 7 days, and zoster-associated pain (ZAP) was monitored monthly thereafter for up to 12 months until pain resolution was achieved. Patients were questioned monthly by telephone, and pain was recorded using a numerical rating scale (NRS, 0-10). Key results A total of 751 of 764 (98.3%) patients completed follow-up. The percentage of patients with ZAP was 12.4% at day 90, 7.1% at 6 months and 4.0% at 1 year. After the third month, the NRS were 3 or less in most of the remaining patients with ZAP. Stratified analysis revealed significant persistence of ZAP in patients aged ≥50 years and in those aged ≥65 years, and in patients with either moderate-to-severe skin symptoms or severe pain at the initial consultation. Stratified analyses unexpectedly showed patients who commenced famciclovir at 0-2 days after onset of the eruption had a higher prevalence of ZAP at day 90 than those treated at 3-5 days or ≥6 days after rash onset (P = 0.0164, log-rank test). On further analysis, a higher proportion of patients (45.4%) treated at 0-2 days had moderate to severe symptoms compared with those treated at 3-5 days (40.5%) or ≥6 days (37.0%) (P = 0.0987, Cochran-Armitage test). Conclusion & Inference This study, with an exceptionally high follow-up rate, revealed several new findings, including the influence of disease severity on the delay between the onset of symptoms and seeking medical attention. Six adverse drug reactions were reported in five of 721 patients in the safety analysis, including two severe cases of vomiting and convulsions.