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Department of Anesthesiology University of Rochester School of Medicine and Dentistry Rochester, NY 14642
The results of recent studies and meta-analyses demonstrate that the antiviral drugs acyclovir, famciclovir, and valacyclovir reduce the risk of developing postherpetic neuralgia (PHN) and the overall duration of herpes zoster pain (1–5). Indeed, routine use of antiviral drugs has been recommended for herpes zoster patients who are at increased risk of prolonged pain and other complications—those who are older, have moderate or severe rash, have moderate or severe pain, or have ophthalmic involvement (6–9). Ahmed et al. (10) recently reported the results of a trial of percutaneous electrical nerve stimulation (PENS) versus famciclovir treatment in 50 patients with acute herpes zoster. In view of the data on the efficacy of antiviral therapy and current treatment guidelines, Ahmed et al.’s (10) conclusion that the results of their trial suggest that PENS "may be a viable alternative to antiviral drugs for the treatment of acute herpes zoster lesions" must be critically evaluated.
In immunocompetent patients, acute zoster is most often an uncomplicated infection that lasts 2–3 wk. What makes herpes zoster a clinical concern is not the lesions, but the unfortunate minority of patients who develop PHN (8,11). Ahmed et al. (10) reported that PENS was "more effective than famciclovir in preventing PHN-related pain symptoms 3 and 6 mo after resolution of the cutaneous lesions." This conclusion was based on comparing the mean pain severity in the antiviral and PENS groups of the few patients with persisting pain in the subset of patients over 50 years of age. But the differences between the two treatments in the percentages of patients with pain at these follow-up times were not statistically significant. There was no evidence, therefore, that PENS prevented PHN, although it may have reduced the intensity of pain in older patients.
Given the very limited evidence provided by Ahmed et al.’s (10) data that PENS significantly attenuated PHN, their conclusion that PENS provides a viable alternative to antiviral drugs must be rejected, and antiviral therapy must remain the standard of care for patients with acute herpes zoster. However, a substantial number of patients with herpes zoster still suffer from prolonged pain, despite adequate antiviral therapy. Although it is possible that new antivirals with greater efficacy will be developed, another strategy for preventing PHN involves supplementing antiviral treatment. The appropriate design in such research on the prevention of PHN is to compare an antiviral agent combined with an investigational treatment (e.g., PENS) with the antiviral agent combined with a placebo matching the investigational treatment (12).
References
Department of Anesthesiology, and Pain Management University of Texas Southwestern Medical Center at Dallas, TX 75235
Dr. Dworkin argues that percutaneous electrical nerve stimulation (PENS) is not a viable alternative to antiviral drugs. Although the results of this preliminary study require validation in a larger series of patients, the fact remains that PENS compared favorably to an antiviral drug in this immunocompetent patient population (1). As pointed out by Dr. Dworkin, "a substantial number of herpes zoster patients still suffer from prolonged pain despite ‘adequate’ antiviral therapy." Therefore, it would be logical to perform a follow-up study evaluating the effects of combining antiviral therapy with PENS therapy (as we had suggested in our manuscript) (1).
Rather than reject a potentially useful new therapy for postherpetic neuralgia, the impressive findings in this Brief Communication will hopefully encourage other investigators to pursue studies with novel modalities like PENS for preventing postherpetic neuralgia. Electroanalgesia is proving to be a useful therapeutic modality for a wide variety of acute and chronic pain syndromes. In many cases, these nonpharmacologic techniques can also "complement" standard pharmacologic therapies. We encourage Dr. Dworkin and his colleagues to support research of promising new therapies rather than simply rejecting them "out of hand" because the numbers are necessarily small in the initial trials.
References
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