We reviewed the evidence about the effect of antiviral medicines for preventing postherpetic neuralgia (PHN).
PHN is a painful condition that can occur after shingles (herpes zoster) in the area where the rash occurred. Many people with PHN find that treatments work only a little or not at all. Attention has therefore turned to stopping the development of PHN. Some people suggested that medicines that target the virus that causes shingles (antiviral medicines), given at the time of the rash, might prevent PHN. The aim of this review was to assess the whether antiviral medicines are able to prevent PHN.
We identified six clinical trials that met our standards for inclusion in the review. They included a total of 1319 participants. We decided that our main measure of whether antiviral medicines work in preventing PHN would be whether or not PHN had developed six months after a first attack of shingles (some of the studies we included of aciclovir measured PHN at four months).
Key results and quality of the evidence
Aciclovir, which is an antiviral medicine, was used in five trials (900 participants) and was not better than a placebo (dummy pill) in preventing PHN. In the other trial (419 participants), famciclovir, which is another antiviral drug, was no better than placebo in preventing pain following healing of the shingles rash. The number of side effects with aciclovir and famciclovir was not very different from the number with placebo. The trials did not have any major problems of design or conduct that put the results in doubt, although most of the reports did not provide enough information to fully assess every aspect. We conclude that according to high quality evidence, oral aciclovir was ineffective in reducing the incidence of PHN and there is not enough evidence on other antiviral treatments. There need to be further well-designed trials of famciclovir or other new antiviral agents with a greater number of participants. Future trials should pay more attention to the severity of pain and quality of life of participants, and should include different groups of people, such as those who have lowered immunity.
The evidence is current to April 2013, when the searches were last updated. Because new evidence on this topic is slow to emerge, we have scheduled the next update of this review for 2017.