Prevention of postherpetic neuralgia with varicella-zoster hyperimmune globulin.
Recovery after an acute attack of herpes zoster is followed by postherpetic neuralgia (PHN) in 9-14% of all patients. Depending on the patient's age, the severity of the acute attack of herpes zoster and the dermatome involved, the incidence of PHN may be as high as 65%. The purpose of our study was to ascertain the incidence of PHN after a prophylactic intravenous injection of varicella-zoster hyperimmune globulin (VZV-IG) (Varitect Biotest Pharma). For this double-blind placebo-controlled randomised investigation we defined PHN as pain confined to the dermatome previously affected by herpes zoster, and we required a pain intensity of at least 15% points on a visual analogue scale (VAS) for this dermatome. The inclusion criteria were the dermatological diagnosis of herpes zoster together with age over 50 years. On Day 1, 20 patients received a single intravenous infusion of VZV-IG in a dose of 2mL/kg body weight, 20 patients (control group) received a single infusion of human albumin 5% in a dose of 2mL/kg body weight. All patients received acyclovir intravenously in a dose of 15mg/kg body weight per 24h for 5 days. The patients were followed up for a total of 42 days. The incidence of PHN at Day 42 was selected as the main outcome criterion for assessing the efficacy of prophylaxis. On reaching a significant difference between the groups (t test; alpha<0.05) in favour of the active treatment group, prophylaxis of PHN by VZV-IG was assessed as effective. Pain was assessed on a VAS and a NAS. As auxiliary outcome criteria, we used the McGill Pain-Rating Questionnaire in its German version, the revised multidimensional pain scale (RMSS) and the Freiburg symptom list (FBL). All results were assessed by the t test (alpha<0.05). The frequency of PHN in the placebo group was 70% (14/20), in the active treatment group it was 35% (7/20) at Day 42. The results of the McGill test showed the variability of the perception of pain in the placebo group significantly greater. No significant group differences were found in the FBL. Being tested with the RMSS, the patients of the placebo group assessed their pains as significantly "more obstinate" (p=0.047). The results can be summed up by saying that VZV-IG not only reduces the incidence of PHN, but also that in certain respects the patients' assessments of their pain experience were different. In our study we found a 50% reduction in PHN incidence However, the outcome time point of our trial was so close to the acute phase of the zoster illness that spontaneous remissions of PHN still have to be taken into account. Despite the widely varied approaches to the problem, reliably effective therapy, let alone 100% prevention of PHN, is still not feasible.