Although there is some variability (depending on the definition of postherpetic neuralgia), about 10% of those with zoster will have persisting pain 1 month after the rash.The main risk factor for postherpetic neuralgia is increasing age; it is uncommon in people aged <50 years, but develops in 20% of people aged 60 to 65 years who have had acute herpes zoster, and in >30% of those people aged >80 years. Up to 2% of people with acute herpes zoster may continue to have postherpetic pain for 5 years or more.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions aimed at preventing herpes zoster and subsequent postherpetic neuralgia? What are the effects of interventions during an acute attack of herpes zoster aimed at preventing postherpetic neuralgia? What are the effects of interventions to relieve established postherpetic neuralgia after the rash has healed? We searched: Medline, Embase, The Cochrane Library, and other important databases up to December 2009 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
We found 41 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
In this systematic review we present information relating to the effectiveness and safety of the following interventions: corticosteroids, capsaicin, dextromethorphan, dressings, gabapentin, herpes zoster vaccine, oral antiviral agents, oral opioid analgesics, lidocaine, topical antiviral agents (idoxuridine), and tricyclic antidepressants.
Pain that occurs after resolution of acute herpes zoster infection can be severe. It may be accompanied by itching and follows the distribution of the original infection. All definitions of postherpetic neuralgia (PHN) are arbitrary and range from 1 month to 6 months after the rash. For clinical trials, neuralgia of 3 months or more has become the most common definition, because resolution of neuralgia after 3 months is slow.
The main risk factor for postherpetic neuralgia is increasing age; it is uncommon in people aged <50 years, but develops in 20% of people aged 60 to 65 years who have had acute herpes zoster, and in >30% of those people aged >80 years.Up to 2% of people with acute herpes zoster may continue to have postherpetic pain for 5 years or more.
Oral antiviral agents (aciclovir, famciclovir, valaciclovir, and netivudine), taken during acute herpes zoster infection, may reduce the duration of postherpetic neuralgia compared with placebo.
We don't know whether topical antiviral drugs, tricyclic antidepressants, or corticosteroids taken during an acute attack reduce the risks of postherpetic neuralgia, as we found few good-quality studies.Corticosteroids may cause dissemination of herpes zoster infection.We don't know whether the use of dressings, oral opioids, or gabapentin during an acute attack reduces the risk of postherpetic neuralgia, as we found no studies.There is limited evidence that gabapentin and oxycodone may reduce the acute pain of herpes zoster.
Gabapentin and tricyclic antidepressants (amitriptyline, nortriptyline) and some opioids (oxycodone, morphine, methadone) may reduce pain at up to 8 weeks in people with established postherpetic neuralgia compared with placebo.Topical lidocaine may be more effective than placebo in treating postherpetic neuralgia.Adverse effects of tricyclic antidepressants are dose related and may be less frequent in postherpetic neuralgia compared with depression, as lower doses are generally used.
Opioid analgesic drugs are likely to be effective in reducing pain associated with postherpetic neuralgia, but they can cause sedation and other well-known adverse effects.We don't know whether dextromethorphan is effective at reducing postherpetic neuralgia.We don't know whether topical counterirritants such as capsaicin reduce postherpetic neuralgia.The zoster vaccine should be used as the primary prevention for herpes zoster and postherpetic neuralgia in people aged >60 years. We don't know whether serotonin–norepinephrine reuptake inhibitors (SNRIs; duloxetine, venlafaxine) or selective serotonin reuptake inhibitors are effective at reducing postherpetic neuralgia.