Antiviral Medications for the Prevention of Post Herpetic Neuralgia after Herpes Zoster Infection

Abstract

Post herpetic neuralgia (PHN) is a condition of persistent, refractory pain in an area previously affected by an acute herpes zoster infection. Age remains an important risk factor for the development of PHN, with 40% of patients older than 50 years and 75% of patients 75 years and older developing PHN after an initial episode of shingles.¹ Persistent pain can lead to significant long‐term problems such as depression, altered activities of daily living, and anorexia.¹ Prior systematic reviews have suggested that treatment with antivirals within 72 hours of the onset of rash may reduce the incidence or duration of PHN.

The Cochrane systematic review discussed here is an update of a previous Cochrane review from 2009, and draws no new conclusions compared to the earlier review. The current review included 6 double‐blinded randomized placebo‐controlled trials and a total of 1211 patients. Five of these trials evaluated oral acyclovir, and the sixth trial evaluated famciclovir. Fifteen other studies were excluded for reasons such as a short follow‐up interval, lack of placebo control, or initiation of treatment beyond 72 hours from the onset of rash.

This review found no significant difference between acyclovir and placebo in the incidence of PHN at 4 months (risk ratio (RR): 0.75, 95% confidence interval (CI) 0.51 to 1.11) or at 6 months (RR: 1.05, 95% CI 0.87 to 1.27). The single study that evaluated famciclovir also failed to show reduced incidence compared to placebo. One trial comparing placebo and acyclovir with 46 participants reported statistically significant lower mean pain scores between two and six months using the VAS validated pain scale. The most common adverse drug events included nausea, vomiting, and headache, but these were not significantly different than in patients who received placebo.

The Cochrane review concludes that there is high quality evidence that acyclovir does not reduce the incidence of PHN and suggests that further trials should focus on famciclovir and other antiviral agents since there is currently insufficient evidence to determine their efficacy.

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