Antiviral treatment for preventing postherpetic neuralgia

Postherpetic neuralgia (PHN) is a painful and refractory complication of herpes zoster. Treatments are either partially or totally ineffective for many people with PHN. Antiviral agents, used at the time of the rash, are one of the best-established approaches that may prevent the development of PHN.

To investigate the effectiveness of antiviral agents in preventing PHN.

We searched the Cochrane Neuromuscular Disease Group Trials Register (January 13 2009), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2008, Issue 4), MEDLINE (January 1966 to November Week 3 2008), EMBASE (January 1980 to Week 02 2009), LILACS (January 1982 to 13 January 2009), and the Chinese Biomedical Retrieval System (January 1978 to 13 January 2009). We checked the references of published studies to identify additional trials.

All randomised and quasi-randomised controlled trials for antiviral treatment given within 72 hours after the onset of herpes zoster for preventing PHN irrespective of any language restrictions.

Two authors independently selected trials and evaluated the methodological quality, then extracted and analysed data from the included trials.

Twenty trials were identified. Twelve trials were excluded and two trials are awaiting classification. Six randomised controlled trials, with a total of 1211 participants were eligible; five trials evaluated oral acyclovir, and one trial with 419 participants evaluated oral famciclovir. There was no significant difference between the oral acyclovir and control groups on the incidence of PHN four months (risk ratio (RR), 0.75; 95% CI 0.51 to 1.11; P = 0.15) or six months (RR 1.05, 95% CI 0.87 to 1.27; P = 0.62) after the onset of the acute herpetic rash. There was some evidence for a reduction in the incidence of pain four weeks after the onset of rash. In the trial of famciclovir versus placebo, neither 500 mg and 750 mg doses of famciclovir reduced the incidence of herpetic neuralgia significantly.

Oral acyclovir did not reduce the incidence of PHN significantly. There is insufficient evidence from randomised controlled trials to determine whether other antiviral treatments prevent PHN. Additional well-designed, randomised controlled trials of famciclovir or other new antiviral agents, with a greater number of participants are needed. Future trials should pay more attention to the severity of pain and quality of life of participants, and should be conducted among different subgroups of people, such as people who are immunocompromised.