No evidence for effectiveness of antivirals in preventing postherpetic neuralgia

Clinical question: 
How effective are antiviral agents for preventing postherpetic neuralgia (PHN)?
Bottom line: 
Oral aciclovir did not significantly reduce the incidence of PHN, defined as pain lasting 120 days or longer from rash onset. There was some evidence for a reduction in the incidence of pain 4 weeks after the onset of rash (NNT* 11 [6 to 56]). There was insufficient evidence from randomised controlled trials to support the use of other antiviral agents (famciclovir) for preventing PHN. No serious adverse effects attributable to the experimental therapy were reported in these trials during treatment, or within 2 weeks of stopping treatment, and non-serious adverse effects were not significantly more common among those receiving antivirals than among control group participants. *NNT = number needed to treat to benefit 1 individual (95% confidence intervals)
Caveat: 
The results of the review were limited to oral antiviral agents (aciclovir and famciclovir), and immunocompetent patients with herpes zoster. Evidence of efficacy on outcomes, such as pain severity and quality of life, could not be shown by these results.
Context: 
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 within 72 hours of the onset of the rash, are one of the best-established approaches that may prevent the development of PHN.
Review CD#: 
CD006866
PEARLS No: 
181
Date: 
July, 2009
Authored by: 
Brian R McAvoy